Biochemistry of Fish Oils

CHAPTER 7

Biochemistry of Fish Oils

T O M O T A R O TSUCHIYA

Government Chemical Industrial Research Institute, Tokyo, Japan

I. Composition and Oxidation 211 A. Chemical Composition 211 B. Oxidation Processes 234

II. Rancidity Problems in Fish 242 A. Introduction 242 B. Development of Rancidity 242 C. Deterioration of Oils in Fish 243 D. Practical Measures 246 References 247

Composition of Fish Oils 247 Seasonal Variations 255 Oxidation of Fish Oils 255 Rancidity Problems in Fish 257

I. Composition and Oxidation

A . CHEMICAL COMPOSITION

1. General Considerations Fish oils, in general, consist predominantly of triglyceryl esters of

fatty acids and minor proportions of free fatty acids, vitamins, coloring matters, hydrocarbons, sterols, phosphatides, etc. However, some kinds of liver oils of elasmobranch fishes contain a relatively large quantity of squalene or glyceryl ether esters of fatty acids; and some fish liver oil (Tsuchiya and Kaneko, 1954 ) x has frequently been found to contain considerable amounts of free fatty acids.

In the predominant proportions of triglyceryl esters of fatty acids, fish oils are similar to vegetable oils and terrestrial animal fats, although some kinds of fish liver oils are exceptions. However, fish oils differ remarkably from vegetable oils in containing a great variety of fatty acids, especially, highly unsaturated fatty acids.2

1 The Reference List at the end of this chapter is divided into sections according to subject matter as follows: Composition of Fish Oils, Seasonal Variations, Oxidation of Fish Oils, and Rancidity Problems in Fish.

2 The statement that an oil contains various fatty acids by no means signifies

211

212 TOMOTARO TSUCHIYA

Besides the fatty acids occurring both in vegetable oils and in terrestrial animal fats, namely, palmitic, stearic, and oleic acids, all fish oils contain both saturated and unsaturated fatty acids of the C 2 0 and C 2 2, and even C 2 4, series. Moreover, fish oils contain highly unsaturated fatty acids —fatty acids having from four to six unsaturated linkages; and especially, marine fish oils contain considerable amounts of these acids. On the other hand, some vegetable oils, semidrying and drying oils, contain great proportions of linoleic or linolenic acid. Linoleic and linolenic acids are, however, not detected with certainty in marine fish oils; and even if these acids occur in fish oils, they would be present in small amounts.

Fish oils are divided into two groups, sea-water (marine) fish oils and fresh-water fish oils; and the two groups differ markedly in their fatty acid composition (Lovern, 1932). In general, sea-water fish oils have a relatively complex composition, and contain great proportions of Ci8, C2o, and C 2 2 acids; whereas fresh-water fish oils contain smaller amounts of C 2 0 and C 2 2 unsaturated acids than sea-water fish oils, but great amounts of palmitic acid and C i 8 unsaturated acids. It has also been found by Tsujimoto (1917b, 1932c) that the bromine content of ether-insoluble bromides of the fatty acids obtained from marine fish oils is generally higher than that of the fatty acids of fresh-water fish oils. Such differences between fresh-water and sea-water fish oils might come from differences in food, environmental conditions, or seasonal conditions (Lovern, 1932).

In this connection, it is to be noted that the oils from the young and adult salmon differ markedly in the fatty acid composition. The oil from salmon parr (young salmon at the initial 1-4 years of their life, living in fresh water) closely resembles the fresh-water fish oils in fatty acid composition, whereas the oil from the adult salmon, which live in the sea, falls in the group of sea-water fish oils. The oils from salmon at various stages of life have been intensively investigated by Lovern (1934 a,b).

Besides all this, there are some other features to be noted which are not only of chemical but also of physiological interest. These are the seasonal variations of oil content in fish (various parts and the whole of the body) and of the composition of oil, and the differences in composi-

that these acids are contained in the free state. Except minor quantities of free fatty acids occurring as a result of unaccountable causes, the fatty acids are present in the form of esters.

7. BIOCHEMISTRY OF FISH OILS 213

tion between the oils of male and female fishes. Some papers dealing with this matter are included in the list of references.

2. Fatty Acids A great number of fatty acids in fish oils have been identified and

their molecular structure largely established. At present, it is known that these fatty acids are normal monobasic aliphatic compounds and, of these acids, unsaturated fatty acids are of the ethylenic type. Moreover, a considerable amount of information has been collected on the relative proportions of fatty acids in various fish oils. Further investigations are, however, required in various aspects.

a. SATURATED F A T T Y ACIDS

Fish oils contain approximately 15-40% (on the weight of total fatty acids) of saturated fatty acids. The chief saturated fatty acid is palmitic acid, Ο ι 6 Η 3 20 2 , and fatty acids occurring in small amounts are myristic acid, C i 4 H 2 80 2 , and stearic acid, C i 8 H 3 60 2. Moreover, fatty acids with less than 14 carbon atoms, arachidic acid, C 2 0H 4 o 0 2 , and behenic acid, C 2 2H 4 40 2 , occur in minute amounts.

Fatty acids with less than 14 carbon atoms have been found in sardine and herring oils. By the fractionation of the fatty acids obtained from about a ton of Japanese sardine oil, Nobori (1940a) found octanoic acid, C 8 H i 6 0 2 , decanoic acid, C i 0 H 2 0O 2 , and lauric acid, C i 2 H 2 40 2 , in very small proportions. He also found traces of these lower saturated acids in herring oil (Nobori, 1940b).

The fatty acid, n-tetracosanoic acid, C 2 4H 4 80 2 , was detected in shark liver oils (Toyama and Tsuchiya, 1927a,b,c). This acid also occurs in sardine oil (Ikuta and Ueno, 1930; Tsuchiya, 1932).

Although isovaleric acid, C 5Hi 0O 2, which occurs in the oils of the marine animals of Delphinidae class, has an odd number of carbon atoms, all fatty acids found in numerous fish oils have even numbers of carbon atoms, and their structures are of the type of straight carbon chain. However, recently, Morice and Shorland (1955) have reported that the fattv acids with odd numbers of carbon atoms, n-pentadecanoic acid, C i 5H 3 0O 2, and n-heptadecanoic acid, C i 7 H 3 40 2 , occur in the liver oil of the New Zealand school shark (Galeorhinus australis Macleay) in amounts of 0.28 and 0.17% of total acids, respectively.

The compositions of saturated fatty acids in various fish oils are illustrated in Tables I and II. In these tables, fish oils are arranged in the order of increasing content of total saturated fatty acids.


b. UNSATURATED F A T T Y ACIDS

(1 ) Monoenoic Acids Although the two monoenoic acids, decenoic acid, Ci 0Hi 8O 2, and

dodecenoic acid (denticetic acid), C12H22O2, have been isolated from sperm whale oil (Toyama and Tsuchiya, 19351,m,n), these acids have not yet been detected in ordinary fish oils.

A tetradecenoic acid (physeteric acid), C i 4H 26 0 2 , was found as a constituent of Japanese sardine oil by Toyama and Tsuchiya (1935b) . Before the discovery in the sardine oil, the acid was first isolated from the head oil of sperm whale by Tsujimoto (1923) . Tsujimoto called it physeteric acid and concluded that the double bond in the acid is situated between fifth and sixth carbon atoms. This acid was also found in dolphin oil (Tsujimoto, 1923), blubber oil of sperm whale (Hilditch and Lovern, 1928), and pilot whale oil (Toyama and Tsuchiya, 1935b).

A hexadecenoic acid, Ο ι 6Η 3 0θ2 , was found in the head oil of sperm whale by Hof Städter (1854) . About five decades after Hofstädter's discovery, Bull (1906) first isolated the acid in a fairly pure state from cod liver oil. Thereafter, it was confirmed by Armstrong and Hilditch (1925) and by Toyama (1927c) that this acid was 9-hexadecenoic acid. At present, the acid is known as palmitoleic acid or zoomaric acid. It has also been found in a number of marine animal oils (Toyama, 1923, 1925a,b, 1926a,b, 1927a; Toyama and Tsuchiya, 1927a,b,c).

Oleic acid, C18H34O2, is widely distributed in fish oils and the other marine animal oils.

Eicosenoic acids, C20H38O2, have hitherto been found in various kinds of marine animal oils. In 1906, Bull (1906) discovered an eicosenoic acid in cod liver oil, and called it gadoleic acid. He also stated that the same acid was found in herring and whale oils. Later, Hilditch and Lovern (1928) found in the body oil of sperm whale an eicosenoic acid, which at that time they described as gadoleic acid. Gadoleic acid has also been found in Sei whale and humpback whale oils (Toyama and Ishikawa, 1934a).

Eicosenoic acids have been found in the oils of several kinds of whale and the liver oils of several kinds of elasmobranch fish (Toyama and Tsuchiya, 1927a,b,c), and in herring oil, plaice oil, and the liver oil of aizame (a species of shark) (Tsujimoto, 1926a,b, 1927a).

However, until 1933, no eicosenoic acid had been isolated with certainty from marine animal oils other than cod liver oil.

In 1933, Takano (1933) isolated from Japanese sardine oil an eico-


senoic acid resembling Bull's gadoleic acid in properties, and determined the constitution to be C H 3 ( C H 2 ) 9 C H = C H ( C H 2 ) 7 C O O H . On the other hand, Toyama and Tsuchiya (1934a) isolated gadoleic acid from a sample of Japanese cod liver oil and confirmed that the constitution was C H 3 ( C H 2 ) 9 C H = i C H ( C H 2 ) 7 C O O H . Moreover, Toyama and Tsuchiya (1934b) isolated an eicosenoic acid in pure state from Japanese sardine oil, from herring oil, and from the liver oil of Alaska pollock (sukeso-dara), and confirmed that the acid was identical with gadoleic acid.

An eicosenoic acid (gondoic acid) has been isolated from pilot wjiale oil by Toyama and Ishikawa (1934b) . It has been confirmed that this acid is an isomer of gadoleic acid. The acid, however, differs from gadoleic acid in the position of ethylene linkage.

Baldwin and Parks (1943) have isolated 11-eicosenoic acid from menhaden body oil. Tsuchiya (1951a) has also separated an eicosenoic acid in pure state from dolphin oil, and shown that the acid is 11-eicosenoic acid. Further, Tsuchiya (1951b) has confirmed that gondoic acid is 11-eicosenoic acid.

Cetoleic acid, C 2 2H 4 20 2 , occurs widely in marine animal oils (Tsuji-moto, 1926a,b; Toyama, 1926c, 1927a; Toyama and Tsuchiya, 1927a,b,c). This acid was first isolated from humpback whale oil by Toyama (1925a) , and was shown to have the constitution of 11-docosenoic acid (Toyama, 1927b).

In 1925, Tsujimoto (1925) discovered a 15-tetracosenoic acid, C 2 4H 4 60 2 , in aizame liver oil (a shark liver oil) and named it selacholeic acid. This acid has not only been detected in several kinds of shark and ray liver oils (Toyama and Tsuchiya, 1927a,b,c) but also isolated from Japanese sardine oil (Tsuchiya, 1932). The acid also occurs in cod liver oil, Sukeso-Dara liver oil, Sei whale oil, and pilot whale oil (Toyama and Tsuchiya, 1935c).

From these results, selacholeic acid seems to be a constituent common to marine animal oils. The acid is identical with the nervonic acid obtained by Klenk (1927) from the cerebroside nervone of brain tissue.

( 2 ) Polyenoic Acids There have hitherto been published a few papers suggestive of the

occurrence of dienoic acids in marine animal oils, but the acids have not yet been detected with certainty.

Polyenoic acids of the C i 6 - C 2 4 series and, perhaps, even C 2 6 series, occur in fish oils. The acids of the C 2 0 and C 2 2 series are the most abundant.


TRIENOIC ACIDS. Hiragonic acid, C i 6 H 2 6 0 2 , (hexadecatrienoic acid) has been isolated from Japanese sardine oil by Toyama and Tsuchiya (1929a, 1935d). According to these investigators, the double bonds of hiragonic acid are situated in the 6-7, 10-11, 14-15 positions. Matsuda (1942a) has isolated a hexadecatrienoic acid in bonito oil; and by the ozonolysis of the methyl ester, he has shown that this acid is 6,10,14-hexadecatrienoic acid.

Tsuchiya (1942a) has detected an octadecatrienoic acid, C i 8H 3 0O 2, in sardine oil and stated that the acid has its double bonds at the 6-7, 10-11, and 14-15; or 6-7, 10-11, and 13-14; or 6-7, 9-10, and 13-14 positions. However, recently, Toyama and Yamamoto (1953b) have reported that the acid is 6, 10, 14-octadecatrienoic acid.

Hata and Kunisaki (1942a) have recognized that an eicosatrienoic acid, C 2 0H 3 4 O 2 (scolic acid), is present in a shark (Scoliodon walbeehmi Bleeker) liver oil. Moreover, the occurrence of 8, 11, 14-eicosatrienoic acid in a fish oil and a shark (Carcharodon carcharias) liver oil is reported by Baudart (1943a) . Adachi (1957a) also has found 6, 10, 14-eicosatrienoic acid in cuttlefish oil.

The occurrence of a docosatrienoic acid, C 2 2H 3 80 2 , in Japanese sardine oil was presumed by Kino (1934) , and the occurrence in the liver oil of a shark (Scoliodon walbeehmi Bleeker) by Hata and Kunisaki (1942b). Later, Baudart (1943a) reported that 8, 11, 14-docosatrienoic acid occurs in the liver oil of a shark (Carcharodon carcharias). Moreover, recently, Adachi (1957b) has reported that 8, 12, 16-docosatrienoic acid was isolated from cuttlefish oil.

TETRAENOIC ACIDS. Hexadecatetraenoic, octadecatetraenoic, eicosatet-raenoic, and docosatetraenoic acids occur in fish oils. Tsuchiya (1940) found a hexadecatetraenoic acid, C 1 6H 2 40 2 , in Japanese sardine oil and suggested that the acid is 4, 8, 11, 14- or 4, 8, 12, 15-hexadecatetraenoic acid (Tsuchiya, 1941). Recently, Toyama and Yamamoto (1953a) stated that it is very probable that this acid is 4, 8, 11, 14-hexadecatetraenoic acid. However, Silk and Hahn (1954) reported that the hexadecatetraenoic acid occurring in South African pilchard oil is 6, 9, 12, 15-hexadecatetraenoic acid.

Moroctic acid, C i 8 H 2 80 2 , 4, 8, 12, 15-octadecatetraenoic acid was found in small amounts in Japanese sardine oil (Toyama and Tsuchiya, 1935e). Also, an octadecatetraenoic acid was isolated from bonito oil by Matsuda and Ueno (1938) . They proved that this acid is 4, 8, 12, 15-octadecatetraenoic acid and is identical with moroctic acid (Matsuda, 1942b).


To the knowledge of this writer, moroctic acid seems to be distributed widely in marine animal oils. A cis-n-octadeca-6, 9, 12, 15-tetraenoic acid was recently isolated from South African pilchard oil (Matic, 1958).

An eicosatetraenoic acid, C20H32O2, has been detected in Japanese sardine oil (Toyama and Tsuchiya, 1935f) and in bonito oil (Matsuda, 1942c). The acid has the double bonds in 4-5, 8-9, 12-13, and 16-17 positions (Toyama and Tsuchiya, 1935f). Recently, Toyama and Yama-moto (1953b) have reaffirmed the eicosatetraenoic acid in Japanese sardine oil to be 4, 8, 12, 16-eicosatetraenoic acid. Besides, the acid seems to be widely distributed in most fish oils. This acid is generally called arachidonic acid to be clearly distinguished from arachidic acid, which is eicosanoic acid (see Section I, A, 2, a ) .

Recently Shimo-oka and Toyama (1954, 1955) have reported that the eicosatetraenoic acid in ox and swine liver lipids is 4, 8, 12, 16-tetraenoic acid and has the same constitution as the eicosatetraenoic acid in sardine oil. On the other hand, before the publication of their report, Arcus and Smedley-Maclean (1943) stated that 5, 8, 11, 14-eicosatetraenoic acid was present in ox suprarenal fat. However, about the eicosatetraenoic acid reported by Arcus and Smedley-Maclean, Shimo-oka and Toyama (1955) have expressed the opinion that the structure appears to be doubtful.

Docosatetraenoic acid, C 22 H 3 60 2, seems to occur widely in marine animal oils (Toyama, 1925a, 1926a,b; Toyama and Tsuchiya, 1927b). Baudart (1943b) noticed the occurrence of 8, 12, 16, 20- or 8, 12, 16, 19-or 8, 12, 15, 19-docosatetraenoic acid in the liver oil of a shark. Later Tsuchiya (1949) isolated a docosatetraenoic acid in fairly pure state from Japanese sardine oil. Moreover, recently, Adachi (1957c) isolated a docosatetraenoic acid from cuttlefish oil, and confirmed that the double bonds are situated in 4-5, 8-9, 12-13, and 16-17 positions. Adachi named the acid caramaic acid.

PENTAENOic, HEXAENOIC, HEPTAENOIC ACIDS. An eicosapentaenoic acid, C20H30O2, has been detected in Japanese sardine oil (Toyama and Tsuchiya, 1935g) and in bonito oil (Matsuda, 1942d). The acid has the double bonds in 4-5, 8-9, 12-13, 15-16, and 18-19 positions. Another eicosapentaenoic acid is reported from South African pilchard oil (Whit-cutt and Sutton, 1956).

A docosapentaenoic acid, C22H34O2 (clupanodonic acid), and a doco-sahexaenoic acid, C 2 2 H 3 20 2, occur as major components in most marine oils. Toyama and Tsuchiya (1935h,i) have suggested that the double


bonds of the docosapentaenoic acid are in the 4-5, 8-9, 12-13, 15-16, and 19-20 positions and the double bonds of the hexaenoic acid in either the 4-5, 8-9, 12-13, 15-16, 18-19, and 21-22 or the 4-5, 8-9, 11-12, 14-15, 17-18, and 20-21 positions. Matsuda (1942e) , also, has isolated a docosapentaenoic acid from bonito oil and showed that the acid is 4, 8, 12, 15, 19-docosapentaenoic acid. Moreover, Matsuda (1942f) has indicated that the docosahexaenoic acid in bonito oil is 4, 8, 12, 15, 18, 21-docosa-hexaenoic acid.

Highly unsaturated C 2 4 acids also occur, but only in small amounts in most marine animal oils. Ueno and Iwai (1934) found an acid of the formula C24H38O2 in the liver oil of Scoliodon laticaudus, and named it scoliodonic acid.

Toyama and Tsuchiya (1934c, 1935j) obtained a highly unsaturated fatty acid having the formula C 2 4 H 3 60 2 from herring, cod liver, pilot whale, and aburazame (a shark) liver oils, and also confirmed the occurrence of the acid in sardine oil. They proposed the name nisinic acid, and reported that it has the double bonds probably in the 4-5, 8-9, 12-13, 15-16, 18-19, and 21-22 positions (Toyama and Tsuchiya, 1935k).

The occurrence of tetracosaheptaenoic acid, C24H34O2 (bonitonic acid), in bonito oil has been reported by Matsuda and Ueno (1939) . Matsuda and Ueno (1939) found, besides bonitonic acid, the acids C 2 4 H 3 80 2 and C24H36O2 in bonito oil. Moreover, Matsuda (1942g) presumed bonitonic acid is 4, 7, 10, 14, 17, 20, 23- or 4, 7, 11, 14, 17, 20, 23-or 4, 8, 11, 14, 17, 20, 23-tetracosaheptaenoic acid.

Highly unsaturated fatty acids containing more than 24 carbon atoms have been detected in a fish oil. Ueno and Yonese (1936a,b) found the acids, C 26 H 4o 0 2 (thynnic acid) and C26H42O2 (shibinic acid), in tunny oil.

The compositions of unsaturated fatty acids in various fish oils are illustrated in Tables I and II .

3. Unsaponifiable Matter

Ordinary fish oils—for example, sardine oil, herring oil, etc.—contain extremely small amounts of unsaponifiable matter. However, some of the liver oils of elasmobranch fishes contain very great amounts of unsaponifiable matter.

The unsaponifiable matter of ordinary fish oils has not yet been sufficiently investigated, but cholesterol is considered to be present in the unsaponifiable matter.


HYDROCARBONS. In 1917, Tsujimoto (1917a) detected a saturated hydrocarbon (iso-octadecane) in basking shark liver oil. Later, Toyama (1925c) investigated a large number of shark liver oils and confirmed that the hydrocarbon is a common constituent of the shark liver oils containing squalene. Toyama, at that time, named the substance pristane, and showed that it has a formula C i 8H 3 8.

Toyama and Tsuchiya (1929b) examined the distillates which were obtained in the course of the superheated-steam deodorization, in vacuum, of hydrogenated fish and sperm whale oils, and found pristane in the unsaponifiable matter. Also, they examined sardine and herring oils, a mixture of fish oils, and sperm whale oil, before hydrogenation, and found that pristane was present as an extremely minor constituent in all the specimens of the oils (Toyama and Tsuchiya, 1935a). Pristane was also found in itoyo fish (Gasterosteus aculeatus) (Ueno and Komori, 1935a). Thus, it seemed probable to assume that the pristane, which had originally been found only in shark liver oils of low specific gravity, occurs widely as an extremely minor constituent in other marine animal oils.

Two views have been expressed on the structure of pristane. Sörensen and Sörensen (1949) have reported that pristane is 2, 6, 10, 14-tetra-methyl pentadecane and has the following constitution:

CHg ^ H 3

C H 3 i I CH 3 > CH ( C H 2) 3CH ( C H 2) 3CH ( C H 2) 3CH <

C H 3' XC H 3

On the other hand, Tsuchiya et al. (1952) have reported that, when the boiling points of iso-octadecane and iso-nonadecane, which have four methyl groups as side chains, are calculated by the rule of Von Weber (1939) , pristane approaches rather to C19H40 than to C i 8H 3 8, but it could not be decided with certainty whether pristane is C i 8 H 3 8 or C19H40. Moreover, considering this result together with other experimental results, they state that if the formula C i 8 H 3 6 is adopted for pristane, pristane is considered to have the following structure:

CH 3

CH 3 I I /C H

3

\ Γ Η / Γ Η rvx/ru \ r w / r - w v r w i y C H ( C H 2) 2C H ( C H 2) 4C H ( C H 2) 2C H < v

C H g / XC H 3

Gadusene, C i 8H 3 2, has been isolated from wheat germ oil by Drummond et al. (1935) . This substance has also been isolated from ishinagi (Stere-


TABLE I FATTY Acm COMPOSITION (WEIGHT PER CENT) OF SEA-WATER FISH OILS

Saturated acids

Oils Total Ci4 ^ 1 6 C

1 8 C

2 0

Body oils of teleostid fish

Jacopever (Sebastichthys capensis)

18.4 2.6 13.8 1.8 0.2 ( ^20-22 )

Herring (Clupea harengus)

18.8-24

5.8-8.3

12.1-16.7

Trace — 0.6

Halibut (Hippoglossus hippoglossus)

19.5 4.0 14.8 0.7

Herring (Clupea harengus)

19.7 7.0 ( C 12 0.1)

11.7 0.8 0.1

Herring 20.4 8.3 12.1 0.3 —

Turbot (Rhombus maximus)

20.6 3.4 15.1 2.1 —

Pilchard (Sardina oceUata)

21.0 5.6 ( C 12 Trace)

13.1 1.4 0.6 ( C 22 0.3)

Sea trout (Salmo trutta)

23.6 2.2 17.0 4.0 0.4

Maasbanker (Trachurus trachurus)

23.8 7.3 ( C 12 0.4)

13.1 2.0 0.4 ( C 22 0.6)

Herring viscera 24.6 5.8 15.7 2.8 0.3

Cape John Dory (Zeus capensis)

25.1 3.1 15.7 4.0 1.8 ( C 22 0.5)

Black pomfret (Stromateus niger)

25.5 4.4 13.3 7.3 0.5


26.3 6.9 17.3 2.1 0.5 ( C 22 0.1)

a (1 ) Minus values followed by Η represent unsaturation in hydrogen atoms. (2 ) Values with asterisk marks in the same Cn-column represent the contents of fatty

acids having different degrees of unsaturation. 0 References for this table appear at the end of Table II.


Unsaturated acidsa

c 1 4 ^ 1 8 C

2 0 ^ 2 2 C

2 4 References0


2.3 12.4 28.5 21.6 16.8 van Rensburg et al. ( - 2 H ) (—2H) (—2.4H) (—7H) (— 9.5H) (1945a)

0.2- 4.7- 16.3- 22.0- 19.5- Lovern (1938) 0.8 7.5 22.2 31.1 27.6

Trace 6.5 23.8 26.9 23.3 Lovern (1937) (—2.6H) ( - 3 H ) (—5.2H) (— 6.5H)

1.2 11.8 19.6 25.9 21.6 0.1 Bjarnason and Meara (—2H) (—2.4H) (— 3.5H) (—5.2H) ( — 4.3H) (— 3.8H) (1944)

0.5 6.4 31.0 28.3 23.1 — Lovern (1938) ( - 2 H ) (—3.4H) ( - 4 . 5 H ) (—5.5H) (— 4.6H)

0.3 8.9 21.7 26.6 21.9 — Lovern (1937) (—2.6H) ( _ 3. 4 H ) (— 6H) ( _ 7.7H)

2.3 17.6 16.2 26.8 16.2 — Black and Schwartz ( - 2 H ) (— 3H) ( - 4 . 3 H ) (—8.8H) (—10.7H) (1950)

0.1 8.8 26.3 19.7 19.0 2.5 Lovern (1937) (—2.4H) (— 3H) (—6.6H) (— 9.2H)

2.8 14.1 19.0 19.4 20.7 0.2 Black and Schwartz ( - 2 H ) (—3H) (—3.8H) (—7.9H) (— 5.3H) (— 4H) (1950)

1.4 10.5 31.8 22.4 9.3 — Hilditch and Pathak (—2H) (—2.5H) (—2.6H) (—7.1H) (—10.5H) (1948)

0.9 9.4 23.4 19.0 21.9 0.3 Black et al. (1946) ( - 2 H ) ( - 2 H ) (—2.5H) ( - 7 H ) (—10.5H) ( - 1 0 H )

2.4 18.8 33.2* 4.5* 3.4* — Karkhanis and Magar ( - 2 H ) (—2H) (—2H) (—2H) (—10H) (1955)

0.4* 6.7* 3.4* ( - 4 H )

1 7* ( - 8 H ) (— 2H)

( - 6 H )

1.9 14.6 19.3 26.3 11.0 — Black and Schwartz ( - 2 H ) (—3.2H) (—3.9H) (—8.8H) (— 9H) (1950)

^ 1 8


Liver oils of teleostid fish Cod

(Gadus morrhua) Pollack

(Gadus pollachius) Jacopever

(Sehastichthys capensis) ( ^ 2 0 - 2 2 )

a ( 1 ) Minus values followed by Η represent unsaturation in hydrogen atoms.

( 2 ) Values with asterisk marks in the same Cn-column represent the contents of fatty acids having different degrees of unsaturation. 0

References for this table appear at the end of Table II.

15.2 1.4 12.3 1.5 —

16.5 2.1 13.0 1.4 —

17.1 1.2 11.6 3.9 0.4

TABLE I (continued)

Saturated acids

Oils Total ^ 1 6 ^ 1 8


Tunny (Thunnus thynnus)

26.4 4.2 18.6 3.5 —

Brown trout (Salmo trutta)

26.6 3.1 19.0 4.5 —


26.9 6.7 17.4 2.1 0.4 ( C 2 20 . 3 )

Lamprey (Petromyzon fluviatilis)

27.8 9.5 17.6 0.7 —

Menhaden (Brevoortia tyrannus)

27.9 8.3 14.9 4.7 —


30.1 5.6 ( C 12 0.5)

19.6 2.0 1.8 ( C 2 20 . 6 )

White pomfret (Stromateus cinerus)

36.6 4.8 20.6 11.2

Pala (Hilsa ilisha)

37.7 5.3 23.5 8.9 0.02

^ 1 8 ^ 1 8

7. BIOCHEMISTRY OF FISH OILS 2 2 3

Unsaturated acidsa

c 1 4 ^ 1 6 ^ 1 8 C

2 0 C

2 2 ^ 2 4 References0

Body oils of teleostid fish — 6.2 26.0 23.5 18.0 Lovern (1936)

(—2.7H) ( —3.2H) (—5.5H) (• — 6.8H)

0.4 11.5 38.3 15.0 8.2 — Lovern (1937) (—2.6H) (—3.9H) ( _ 7 . 8 H ) (• —10.1H)

1.9 15 19.8 25.8 10.6 — Black and Schwartz ( - 2 H ) (—3.5H) (—4.1H) (__9.4H) (· — 9.2H) (1950)

— 10.9 35.3 15.3 10.7 — Lovern (1937) (—2.1H) ( —2.6H) (__6.5H) (• —10.3H)

5.8 23.4 31.1 8.4 3.4 Baldwin and Lanham ( C 12 Trace) (1941)

2.1 7.4 23.2 20.5 14.7 1.9 Black et al (1946) ( - 2 H ) ( - 2 H ) (—3.6H) 7.3H) (-— 9.8H) ( - 1 0 H )

1.4 9.2 33.2* 7.5* — — Karkhanis and Magar ( - 2 H ) (—2H) (—2H) (—2H) (1955)

3.6* 5.1* ( - 4 H ) ( - 8 H )

3.6* ( - 6 H )

1.3 6.8 32.9* 9.0* 0.5 — Karkhanis and Magar ( - 2 H ) ( - 2 H ) ( - 2 H ) ( - 2 H ) (-—10H) (1955)

1.7* 0.5* ( - 4 H ) ( - 8 H )

9.7* ( - 6 H )

Liver oils of teleostid fish

1.7 8.2 25.7 27.3 21.9 — Harper and Hilditch ( - 2 H ) ( - 2 H ) (—3.3H) (—5.5H) ( - - 7.4H) (1937)

10.9 34.2 25.4 13.0 — Lovern (1937) (—2.7H) 5.4H) ( - - 6.5H)

0.6 13.5 46.3 12.7 7.5 2.4 van Rensburg et al ( - 2 H ) (—2H) ( — 2.3H) (-—6.3H) (-- 8.5H) (1945a)


TABLE I (continued) Saturated acids

Oils Total c 1 4 ^ 1 6 ^ 1 8 C

2 0


Ling (Genypterus bfocodes)

17.7-24.0

0.7-2.2

15.8-18.0

1.2-3.8

—

Red cod (Physiculus backus)

19.1 1.6 14.4 3.1 —

Ling (Genypterus blacodes)

21.4 1.9 16.9 2.6 —

Hake (Merluccius gayi)

21.7 2.1 18.4 1.2 —

Hake (Merluccius capensis)

21.7 1.4 17.9 1.9 0.5 ( C-20-22 )

Catfish (Anarrhichas lupus)

21.7 1.5 17.9 2.3 —


23.2 3.9 15.2 3.9 0.2

Grouper (Polyprion oxygeneios)

24.5 1.9 19.3 3.3 —


25.1 3.4 15.2 3.7 1.7 ( C 2 2l . l )

Tunny (Thunnus thynnus)

26.8 — 17.9 8.9 —


28.0 2.0 22.7 3.3 —


28.8 2.4 23.0 3.4 —

Liver oils of elasmobranch fish

Ratfish (Chimaera monstrosa)

17.3 — 8.4 7.2 1.3 ( C 22 0.4)

School shark (Galeorhinus australis)

20-29

1.3-3.9

15.2-17.1

3.4-6.5

0.1-1.5

Angel fish (Squatina angelus)

20.4 1.4 17.0 2.0

a Minus values followed by Η represent unsaturation in hydrogen atoms. & References for this table appear at the end of Table II.


Unsaturated acids0

Ci4 C

1 6 ^ 1 8 C

2 0 C

2 2 C

2 4 References6


0.1- 5.5- 16.9- 21.9- 8.3- Shorland (1939) 1.1 9.4 38.4 36.6 17.1

7.7 30.7 28.2 14.3 Shorland and Hilditch (• —2H) ( - 3 H ) (—6.5H) (—10.3H) (1938)

6.5 34.9 25.1 12.1 Shorland (1939) (-—2H) (—2.5H) (—5H) (— 7.6H)

9.3 37.3 21.0 10.7 Shorland and Hilditch (-—2H) (—2.6H) (—5.7H) ( - 8H) (1938)

0.4 11.8 32.6 19.3 12.0 2.3 van Rensburg et al. ( - 2 H ) (• —2H) (—3.3H) ( - 7 . 1 H ) ( - 9H) (1945b)

— 11.7 46.8 12.0 5.9 1.9 Lovern (1937) (• —2.2H) (—2.6H) (—6.4H) (— 8.2H)

1.0 9.5 34.9 15.0 12.8 3.6 Black et al. (1946) (—2H) (• —2H) (—2.8H) (—6.9H) (—10.5H) (—10H)

0.1 17.3 45.2 9.1 3.8 — Shorland and Hilditch ( - 2 H ) (-- 2 H ) (—-2.3H) (—6.3H) (— 6.3H) (1938)

0.95 8.5 32.8 20.2 12.5 — Black et al. (1946) ( - 2 H ) (-- 2 H ) (—2.6H) (—5.7H) (—10H)

— 3.4 23.5 28.2 18.1 — Lovern (1936) (--2 .5H) (—2.8H) (—5.5H) (— 7.4H)

0.2 18.2 40.8 8.8 4.0 — Shorland and Hilditch ( - 2 H ) (-- 2 H ) (—2.4H) (— 6H) ( - 6H) (1938)

1.6 23.3 39.3 7.0 Trace — Shorland and Hilditch ( - 2 H ) (-- 2 H ) (—2.5H) (—5.9H) (1938)

Liver oils of elasmobranch fish

— 2.5 50.6 19.6 7.9 2.1 Lovern (1937) (—2.2H) (—2.9H) (— 3.5H)

0.6- 5.3- 26.5- 15.5- 19.6- 0- Oliver and Shorland 1.2 6.2 31.7 20.7 25.3 2.2 (1948) — 6.5 20.7 21.9 30.5 — Lovern (1937)

( —2H) ( - 3 H ) (—6H) (—10.2H)


TABLE I (continued)

Oils Saturated acids

Oils Total ^ 1 6 ^ 1 8 Liver oils of elasmohranch fish

Spotted dogfish 2 0 . 7 1.7 1 5 . 7 3 . 3 — (Scyllium canicuh)

Soupfin shark, females 2 3 . 2 3 . 3 1 7 . 7 1 .6 0 .7 (Galeorhinus cants)

Soupfin shark, foetuses 2 4 . 6 3 . 3 1 8 . 5 2 . 2 0 . 5 ( C 2 20 . 1 )

Soupfin shark, thin females 2 6 . 0 3 . 5 1 7 . 3 3 . 6 1.2 ( C 22 0 . 4 )

Basking shark 2 6 . 1 2 . 1 1 3 . 6 3 . 2 3 . 6 (Cetorhinus maximus) ( C 2 2 3 . 2 )

( C 2 40 . 4 )

School shark 2 6 . 8 3 . 9 1 6 . 7 5 . 3 0 .1 (Galeorhinus australis) ( C 2 21 . 0 )

Seven-gilled shark 2 8 . 0 1 .6 1 6 . 6 6 . 9 1.3 (Heptranchias pectorosus) ( C 2 21 . 6 )

Shark 3 1 . 2 3 . 1 1 8 . 5 9 . 5 0 .1 (Carcharias mehnopterus)

Sping shark 3 1 . 7 3 . 9 2 0 . 4 6 . 9 0 . 3 (Echinorhinus spinosus) ( C 22 0 . 2 )

Shark 3 3 . 7 4 . 4 1 8 . 5 9 . 0 1.8 (Carcharias mehnopterus) ( C 1 2 Trace)

Saw fish 3 6 . 9 1.2 2 2 . 9 1 2 . 7 0 .1 (Pristis cuspidatus)

Embryo shark 3 8 . 8 8 . 6 2 5 . 1 5 .1 — (Galeocerdo tigrinus)

Shark 3 9 . 9 1 .5 2 3 . 6 1 4 . 5 0 . 3 (Galeocerdo raynen)

Shark 4 0 . 9 3 . 3 2 4 . 9 1 1 . 1 1.2 (Galeocerdo rayneri) ( C 1 2 0 . 4 ) ( C 24 0 . 0 4 )

Mature shark 4 3 . 2 3 . 0 2 5 . 1 1 3 . 8 1.3 (Galeocerdo tigrinus)

a Minus values followed by Η represent unsaturation in hydrogen atoms. 0 References for this table appear at the end of Table II.

^ 1 8 ^ 1 8


Unsaturated acids*

c 1 4 ^ 1 6 C

1 8 C

2 0 C

2 2 C

2 4 References0

Liver oils of elasmobranch fish — 4.0 25.3 24.4 24.8 Lovern (1937)

(—2.2H) ( - 3 H ) (— 6.4H) (— 9.2H)

0.5 9.4 25.3 24.4 15.9 1.2 Karnovsky et al. (—2H) (—-3.1H) (—3.7H) (—βΗ) (—10.3H) (—10H) (1948c)

0.7 6.3 17.5 20.9 25.5 4.6 Karnovsky et al. (—2H) (—2H) ( - 3 . 4 H ) (—8.3H) (— 10.6H) ( - 1 0 H ) (1948c)

1.0 8.6 23.1 17.2 17.5 6.4 Karnovsky et al. (—2H) (—2H) (—2.6H) (— 6.5H) (— 9.8H) (—10H) (1948c)

( C 26 0.2, —10H)

0.5 11.9 12.8 23.2 20.0 5.6 Karnovsky et al. (—2H) ( —2H) (—2.3H) (—4H) (— 3.6H) (— 5.9H) (1948a)

0.7 5.3 26.5 15.5 22.8 2.2 Oliver and Shorland (—2H) (—2H) (—2.3H) (—4.5H) (— 6.5H) ( - 4H) (1948)

0.7 11.0 30.3 15.6 13.0 1.4 Karnovsky et al. (—2H) (—2H) (—2.5H) ( _ 5.4H) (— 8.7H) (—10H) (1948b)

0.8 10.8 19.7 15.2 17.1 5.3 Pathak and Suwal (—2H) (—2.1H) (—3.6H) (— 6H) (— 8.8H) (—11H) (1954)

1.6 11.9 25.6 15.4 13.9 — Karnovsky et al. (—2H) (—2H) ( - 3 H ) ( — 6.6H) (— 8.1H) (1948a)

2.8 12.8 19.9 19.0 7.3 4.3 Pathak and Pande (—2H) (—2.1H) ( - 4 H ) 6.8H) (— 9.9H) (—11H) (1955)

0.3 8.2 28.5 16.4 5.2 4.6 Pathak and Suwal (—2H) (—2H) (—2.2H) (— 5.3H) ( _ 7.4H) ( - 1 1 H ) (1954)

0.2 18.0 38.2 3.9 — — Pathak and Suwal (—2H) (—2H) (—2.1H) (— 4.4H) (1955)

0.2 10.9 23.3 11.6 12.2 1.9 Pathak et al. (1952) (—2H) (—2H) (—2.6H) (— 5.8H) ( — 8.4H) (—11H)

1.1 11.2 19.6 22.3 4.8 — Pathak et al. (1952) (—2H) (—2.6H) (—3.9H) (— 7H) (—• 10.6H)

( C 12 0.13) 0.4 7.8 23.6 15.5 9.3 — Pathak and Suwal

(—2H) (—2H) (—2.6H) (— 5.6H) (— 10.5H) (1955)

2 2 8 TOMOTARO TSUCHIYA

TABLE II FATTY ACID COMPOSITION ( WEIGHT PER CENT ) OF OILS OF FRESH-WATER FISH

Saturated acids

Oils Total Ci4 ^ 1 6 ^ 1 8 ^ 2 0

Pahuma, liver (WaUago attu)

19.7 1.5 14.2 4.0 —

Salmon parr, body (Salmo salar)

24.4 2.7 ( C 12 0.7)

17.7 3.3 —

Nain, body (Cirrhina mrigala)

26.4 1.9 21.4 3.1 —

Bhakur, liver (Catla buchanani)

29.1 0.6 19.0 6.4 3.1

Nain, viscera (Cirrhina mrigala)

32 5.7 20.1 5.7 0.5

Rohu, body (Labeo rohita)

36.6 3.4 21.2 11.5 0.5

Bhakur, viscera (Catla buchanani)

37.4 2.8 25.3 7.9 1.4

Bhakur, body (Catla buchanani)

38.3 2.9 28.9 6.5 —

Rohu, viscera (Labeo rohita)

45.3 1.6 26.0 14.6 3.1

a Minus values followed by Η represent unsaturation in hydrogen atoms.

References to Tables I and II

Baldwin, W. H., and Lanham, W. B. (1941) . The chemistry of menhaden oil. Ind. Eng. Chem. Anal. Ed. 13, 615-616.

Bjarnason, Ο. B., and Meara, M. L. (1944) . The mixed unsaturated glycerides of liquid fats. V. Low-temperature crystallization of Icelandic herring oil. /. Soc. Chem. Ind. (London) 63, 61-63.

Black, Μ. M., and Schwartz, Η. M. (1950) . South African fish products. XXXI. The composition of pilchard oil and of maasbanker oil. / . Sei. Food Agr. 1, 248-251.

Black, Μ. M., Rapson, W. S., Schwartz, Η. M., and van Rensburg, Ν. J. (1946) . South African fish products. XX. Mode and degree of fat storage in the Cape John dory (Zeus capensis C. and V.) in relation to the chemical compositions of the liver and body fats. /. Soc. Chem. Ind. (London) 65, 13-15.

Harper, D. Α., and Hilditch, T. P. (1937) . The component acids and glycerides of partly-hydrogenated marine animal oils. III. North Sea cod liver oil. /. Soc. Chem. Ind. (London) 56, 322-329T.

Hilditch, T. P., and Pathak, S. P. (1948) . The component acids of herring visceral fat. Biochem. J. 42, 316-320.


Unsaturated acids*

c 1 4 1̂6 1̂8 2̂0 c 2 2 2̂4 References

0.4 8.4 32.6 19.8 19.1 Pathak and Agarwal (• —2H) (—2.4H) (—5.3H) (- - 8H) (1952)

3.1 21.7 30.0 12.9 9.9 — Lovern (1934) Ο — 2 H ) (-—2.3H) (—3.8H) (—8.3H) (• —10.2H)

3.7 32.6 29.5 5.0 2.8 Pathak et al. (1954) ( - 2 H ) (-—2.2H) ( _ 3 . 6 H ) ( _ 4 . 9 H ) (-- 6H)

Trace 7.0 25.4 26.5 9.4 2.6 Pathak and Agarwal (• —2.7H) (—4.8H) (—6.5H) (-- 8H) (1952)

4.2 26.5 32.3 5.0 — — Pathak et al (1954) ( - 2 H ) (-—2.2H) (—2.9H) (—4.6H)

3.7 8.1 32.2 12.4 6.7 0.3 Pathak et al (1954) ( - 2 H ) (• —2.2H) (—3.3H) (—5.2H) (• — 6.9H) (—8H)

1.4 10.0 37.2 11.9 2.1 — Pathak and Agarwal (• —2.7H) (—2.5H) ( - 5 . 7 H ) (• — 9H) (1952)

0.2 25.3 17.9 7.5 10.1 0.6 Pathak and Agarwal (-—2.7H) (—2.5H) (—5.7H) (· — 9H) (1952)

0.7 8.6 30.3 9.6 5.5 — Pathak et al (1954) ( - 2 H ) (-—2.7H) ( _ 3 . 6 H ) (—6.3H) (• — 9H)

Karkhanis, Y. D., and Magar, N. G. (1955) . Component fatty acids in body fats of some marine fishes. / . Am. Oil Chemists' Soc. 32, 492-493.

Karnovsky, M. L., Rapson, W. S., Schwartz, Η. M., Black, Μ. M., and van Rens-burg, N. J. (1948a). South African fish products. XXVII. The composition of the liver oils of the basking shark (Cetorhinus maximus Gunner) and the spiny shark (Echinorhinus spinosus Gmelin). / . Soc. Chem. Ind. (London) 67, 104-107.

Karnovsky, M. L., Rapson, W. S., and Schwartz, Η. M. (1948b). South African fish products. XXVIII. The composition of the liver oil of the seven-gilled shark (Heptranchias pectorosus). J. Soc. Chem. Ind. (London) 67, 144-147.

Karnovsky, M. L., Lategan, A. W., Rapson, W. S., and Schwartz, Η. M. (1948c) . South African fish products. XXIX. The composition of the liver oil of the soupfin shark (Galeorhinus canis Rond). / . Soc. Chem. Ind. (London) 67, 193-196.

Lovern, J . A. (1934) . Fat metabolism in fishes. V. The fat of the salmon in its young fresh-water stages. Biochem. J. 28, 1961-1963.

Lovern, J . A. (1936) . Fat metabolism in fishes. X. Hydrogenation in the fat depots of the tunny. Biochem. J. 30, 2023-2026.


Lovern, J . A. (1937) . Fat metabolism in fishes. XI. Specific peculiarities in depot fat composition. Biochem. J. 31, 755-763.

Lovern, J . A. (1938) . Fat metabolism in fishes. XII. Seasonal changes in the composition of herring fat. Biochem. J. 32, 676-680.

Oliver, A. P., and Shorland, F . B. (1948) . New Zealand fish oils. 5. Composition of the fats of the school shark (Galeorhinus australis Macleay). Biochem. J. 43, 18-24.

Pathak, S. P., and Agarwal, C. V. (1952) . The component acids of the fats of some Indian fresh-water fish. Biochem. J. 51, 264-268.

Pathak, S. P., and Pande, G. D. (1955) . Component fatty acids of Indian shark liver oil. J . Am. Oil Chemists' Soc. 32, 7-9.

Pathak, S. P., and Suwal, P. N. (1954) . Component fatty acids of marine fish liver oils. J . Am. Oil Chemists' Soc. 31, 332-334.

Pathak, S. P., and Suwal, P. N. (1955) . Composition of liver fats of mature and embryo sharks (Galeocerdo tigrinus). J. Am. Oil Chemists' Soc. 32, 229-230.

Pathak, S. P., Agarwal, C. V., and Mathur, S. S. (1952) . Component fatty acids of Indian shark liver oils. / . Am. Oil Chemists' Soc. 29, 593-596.

Pathak, S. P., Pande, G. D., and Mathur, S. S. (1954) . The component acids of the fats of some Indian fresh-water fishes. Biochem. J. 57, 449-453.

Shorland, F . B. (1939) . New Zealand fish oils. III. The composition of the depot fats of the ling (Genypterus bhcodes). Biochem. J. 33, 1935-1941.

Shorland, F . B., and Hilditch, T. P. (1938) . The component fatty acids of some New Zealand fish oils. Biochem. J. 32, 792-796.

van Rensburg, Ν. J . , Rapson, W. S., and Schwartz, Η. M. (1945a). South African fish products. XVI. The component acids of the head, body, liver, and intestinal oils of Jacopever (Sebastichthys capensis Gmel.). / . Soc. Chem. Ind. (London) 64, 139-140.

van Rensburg, Ν. J . , Rapson, W. S., and Schwartz, Η. M. (1945b). South African fish products. XVII. The component acids of the liver oil of the stockfish (Merluccius capensis Cast.). / . Soc. Chem. Ind. (London) 64, 140-143.

olepsis ischinagi) liver oil by Nakamiya (1935) . However, the substance is not the same as the hydrocarbon separated by Tsujimoto (1931) from ishinagi liver oil.

Zamene, C i 8H 3 6, has been detected from the basking shark liver oil (Tsujimoto, 1935a,b). However, according to the recent report by Lederer and Pliva (1951) , the formula is C 1 9 H 3 8 , and the constitution possibly 2, 6, 10, 14-tetramethyl-pentadec-l-ene.

A highly unsaturated hydrocarbon, squalene C30H50, was first isolated from the liver oil of black shark (Tsujimoto, 1906). This substance occurs in the liver oils of various sharks of the family Squalidae (Tsujimoto, 1916, 1917c, 1918, 1920). Of the liver oils of these sharks, the liver oil of aizame (a shark) contains squalene up to more than 8 0 % by weight. In


general, if sharks possess squalene in their livers, their eggs seem to contain the same hydrocarbon. Squalene is 2, 6, 10, 15, 19, 23-hexamethyl-tetracosa-2, 6, 10, 14, 18, 22-hexaene (Karrer and Helfenstein, 1931; Heil-bron et al., 1926). Moreover, it is of interest to note that if the shark liver contains a large amount of squalene, it seems to contain a smaller amount of vitamin A.

Highly unsaturated hydrocarbons similar to squalene occur in various marine animal oils (Tsujimoto and Kimura, 1927; Tsujimoto, 1930a, 1931; Tsuchiya, 1952; Tsuchiya and Kato, 1950; Tsuchiya and Tanaka, 1958; Tsuchiya and Mamuro, 1958).

HIGHER ALIPHATIC ALCOHOLS. Besides hydrocarbons, alcohols have been found as unsaponifiable matters in fish oils.

Cetyl alcohol, C i 6 H 3 40 , occurs in the oil of ingwandarame fish (Ru-vettus tydemani Weber) (Kimura, 1926), in cuttlefish oil (Tsujimoto, 1930b), in visceral oil of Laemonema morosum (Komori et al., 1956), and in the body oil of Xenogramma carinatum Weite (Matsumoto et al., 1955).

Hexadecenyl alcohol, C i 6 H 3 20 , occurs in ingwandarame fish oil (Kimura, 1926).

Oleyl alcohol, C i 8 H 3 60 , occurs in the liver oil of rabukazame (a species of shark) (Toyama, 1925g), in ingwandarame fish oil (Kimura, 1926), in cuttlefish oil (Tsujimoto, 1930b), in itoyo fish (Gasterosteus aculeatus) oil (Ueno and Komori, 1935a), in the liver oil of Theragra chalcogramma (Ueno and Komori, 1935b), and in visceral oil of Laemonema morosum (Komori et al., 1956). Moreover, this alcohol has been found in the body oil of Xenogramma carinatum Weite, and constitutes the major portion of the unsaponifiable matter of the oil (Matsumoto et al., 1955).

The alcohol, 11-docosenol, C22H44O, has been found in a large amount ( 5 0 % of unsaponifiable matter) in the liver oil of Laemonema morosum (Komori and Agawa, 1954; Komori et al., 1956).

C2o-~C 24-monoethenoid alcohols and C 2 2- , C 2 4- , and C2 8-diethenoid alcohols have been found in the liver oil of Laemonema morosum (Ueno and Matsushima, 1957).

Highly unsaturated alcohols occur in itoyo fish oil (Ueno and Komori, 1935a) and in the liver oil of Laemonema morosum (Ueno and Matsushima, 1957).

GLYCEROL ETHERS. Batyl alcohol, 0 2 ι Η 4 40 3 , and selachyl alcohol, C 2 i H 4 20 3 , were isolated first from the liver oil of a shark (Hexanchus


griseus) by Tsujimoto and Toyama (1922) . Later, the two alcohols were found to occur in the liver oils of four species of shark (Toyama, 1925e), in the egg oil of Squalus suckleyi Girard (Tsujimoto, 1932a; Ono, 1932), and in cuttlefish oil (Tsujimoto, 1930b). Moreover, batyl alcohol was detected in the hydrogenated product of unsaponifiable matter obtained from cod liver oil (Nakamiya and Kawakami, 1927).

Chimyl alcohol, C 1 9 H 4 0 O 3 , a homologue of batyl alcohol, was found in the liver oil of a shark {Chimsera barbouri Garman) by Toyama (1925d), and later in cuttlefish oil by Tsujimoto (1930b) .

The above three alcohols are distributed widely in marine animal oils, especially, shark and ray liver oils, and are considered to be important constituents of elasmobranch fish liver oils (Tsujimoto, 1936).

The constitutions of these alcohols have been investigated by Toyama (1925d), by Heilbron and Owens (1928) , and by Davies et al. (1933) . According to these investigators, the compounds described, in the above, as selachyl, batyl, and chimyl alcohols, are respectively α-oleyl-, a-octa-decyl-, and α-cetyl-glycerol ethers.

Highly unsaturated glycerol ethers occur in the liver oil of Squalus suckleyi Girard (Toyama, 1925f). According to Toyama and Ishikawa (1938) , the highly unsaturated glycerol ethers in the liver oil of Squalus suckleyi Girard consist chiefly of C 2 5 H 4 2 O 3 , and include C 2 3 H 4 0 O 3 and C 2 5 H 4 4 O 3 . Of the three glycerol ethers, the ether, C 2 5 H 4 2 0 3 , has the structure, C H 2 O C 2 2 H 3 5 C H O H C H 2 O H and the ether, C 2 3 H 4 0 O 3 , the structure, C H 2 O C 2 o H 3 3 C H O H C H 2 O H (Toyama and Takahashi, 1939). Also, recently, Ueno and Matsushima (1957) detected highly unsaturated glycerol ethers in the liver oil of Laemonema morosum.

VITAMINS AND ALLIED COMPOUNDS. Vitamins A and D occur widely in fish liver oils. The liver oil of Stereolepis ischinagi Hilgendorf contains a considerable amount of vitamin A. Tsujimoto (1932b) has reported that cod liver oil units for 12 specimens of the liver oils of Stereolepis ischinagi were 120-2800. Also, Ueno et al. (1928) reported that the vitamin A content of the liver oil of Stereolepis ischinagi was several hundred times as much as that of cod liver oil. However, a specimen of the oil of Stereolepis ischinagi examined by Tsuchiya and Tanaka (1957) contained hardly any vitamin A, but seemed to contain a considerable amount of kitol.

Tsuchiya and Tanaka (1957) have reported that the liver oil of tunny contains, besides vitamin A, a relatively large amount of kitol and anhy-drovitamin A or a compound resembling anhydrovitamin A.


The oils from pyrolic caeca of cod and pollack also constitute a good source of vitamin A.

NOTE ON SOME OTHER MINOR COMPOUNDS. As to the coloring matters

in fish oils, few investigations have been made, and, insofar as this writer knows, the available papers treat of the coloring matters found only in pilchard and salmon oils. In pilchard oil, carotene, xanthophyll, and fucoxanthin have been found by Bailey (1938) ; and in salmon oil, astacin has been found by Sörensen (1935) .

Phosphatides seem to be present in a considerable amount in some kinds of fish liver oils such as bonito liver oil, tunny liver oil, etc.; but little information has hitherto been available concerning their presence in the depot oils of fishes.

4. Glycerides

A fish oil, as has been noted previously, consists chiefly of triglyceryl esters (i.e., triglycerides) of fatty acids; but so far no mention has been made of the kinds of such glycerides. Therefore, various component glycerides in fish oils will here be briefly reviewed.

Although various fatty acids are contained in the fish oil, these acids seem to be heterogeneously distributed among glycerol molecules, with the result that various triglycerides are formed. According to the calculation of possible random arrangements of fatty acids in glycerol molecules, the triglycerides supposed to constitute fish oils are numerous, but it is not evident how many kinds of triglycerides are present in fish oils. However, up to the present time, some of the triglycerides in a few fish oils have been brought to light.

TRIGLYCERIDES

Some of the triglycerides in cod liver oil, herring oil, sardine oil, shark liver oil, and cuttlefish oil, are listed in the literature, and these are summarized below:

COD LIVER OIL. The compounds have been investigated by Suzuki and Masuda (1928) and by Harper and Hilditch (1937) . Suzuki and Masuda separated the following triglycerides in the form of bromo-addi-tion products by the solubility differences in various solvents: zoomaro-Ci 8H 270-clupanodonin, zoomaroarachidonoclupanodonin, arachidono-Ci 8H 270-clupanodonin, clupanodonodiarachidonin, Ci 8H 270-diclupano-donin, etc.

On the other hand, Harper and Hilditch made the investigation by the catalytic hydrogenation technique, where the hydrogenation was


carried out to varying extents, and indicated that cod liver oil consists of a complex mixture of mixed triglycerides, and each kind of triglyceride contains at least two, and usually three, different kinds of fatty acids.

HERRING OIL. The compounds have been investigated by Suzuki (1929a), and the types of the triglycerides by Bjarnason and Meara (1944) . Suzuki separated the following triglycerides by the same technique as used in the investigation of the triglycerides in cod liver oil: zoomaroarachidonoclupanodonin, gadoleodiarachidonin, tricetolein, etc.

According to Bjarnason and Meara (1944) , the following types of triglycerides constitute the herring oil: ( J ) disaturated-monounsaturated, 3.7 mole %; ( 2 ) monosaturated-diunsaturated, 61.0 mole %; ( 3 ) triun-saturated, 35.3 mole %.

SARDINE OIL. The compounds have been investigated by Suzuki (1929a) and by Tsuchiya (1942b). Suzuki separated the following triglycerides by the technique indicated above: triolein, triarachidonin, oleodicetolein (C22H3 50 ) 2-arach idon in , etc.

On the other hand, Tsuchiya isolated the first of the following solid triglycerides, and presumed the others might be predominating in the respective fractionation products: eicosatetraenodipalmitin, myristodi-palmitin, tripalmitin, oleodipalmitin, oleostearopalmitin, stearodipalmitin.

SHARK LIVER OIL. The compounds have been investigated by Suzuki (1929b) by the same technique as indicated above, and the following are reported: trizoomarin, palmitodiolein, triolein, triarachidonin, clu-panododiarachidonin, arachidonodiclupanodonin, etc.

CUTTLEFISH OIL. A triglyceride, myristopalmitostearin, has been isolated by Takao and Tomiyama (1954) .

B. OXIDATION PROCESSES

Fish oils, as well as other edible oils and fats, if conditions are favorable, spontaneously oxidize in the presence of atmospheric oxygen, at or near the ordinary temperatures. This type of oxidation is called autoxida-tion. In the present section, the process and the results of autoxidation (see Swern et al., 1948), are briefly discussed and at the same time, a brief description is made of antioxidants (see also Holman, 1954).

1. General Considerations

It has long been recognized that the autoxidation of an oil proceeds in two fairly well-defined stages. In the initial stage (comprising the so-called induction period), oxygen is absorbed by the oil at a moderate rate, and in the later stage, it is absorbed at an accelerating rate.


The main reaction in the initial stage is the formation of peroxide. The peroxide, however, does not accumulate rapidly, but its content increases roughly in proportion to the amount of oxygen absorbed. According to an older theory, the peroxide is formed by the direct addition of an oxygen molecule to the double bond in the fatty acid chain, in the following scheme:

— C H = C H — + 0 2 > _ C H — C H — I I

ο — ο

However, recent investigators consider that the main reaction is the formation of another type of peroxide, a hydroperoxide, in which the original number of double bonds is retained. An experimental finding supporting this view was presented first by Farmer and Sutton (1943a) . They isolated a nearly pure methyl hydroperoxido-octadecenoate from the autoxidized methyl oleate, and stated that the mono-hydroperoxide retained the olefinic unsaturation of the oleic ester intact and was formed by the substitution of —OOH group in the oleic chain at one or other of the methylene groups adjacent to the double bond.

The mechanisms of the formation of hydroperoxides from such individual fatty acids as oleic, linoleic, and linolenic acids have been reported. However, since linoleic and linolenic acids have not yet been found with certainty in fish oils, the mechanisms of the formation of hydroperoxides from these acids will not be considered here.

The formation of hydroperoxide in the autoxidation of methyl ester of oleic acid has been intensively investigated by various workers, and an interesting theory of the mechanism of hydroperoxide formation has been developed. This theory assumes that hydroperoxide is formed by a chain reaction initiated by the removal of a hydrogen atom from the alpha-methylene group, as follows:

— H- + 0 2

— C H 2— C H = C H > — CH—CH=CH >

+ Η· (from fresh molecule) —CH—CH=CH > —CH—CH=CH—

OO- OOH

Should this mechanism be correct, there should occur resonance between the three-carbon systems:

χ y ζ —CH—CH=CH—

χ y ζ —CH=CH—CH—


and oxygen could attack at the 8, 9, 10, or 11 position, giving rise to four isomeric hydroperoxides.

On the other hand, Gunstone and Hilditch (1946) have proposed that the primary step is the direct addition of an oxygen molecule to the double bond, and not to an adjacent methylene group, and the subsequent step is the transformation into hydroperoxide with the formation of a new ethenoid bond.

+ o2

—CH=CH—CH 2 > —CH—CH—CH2

I I ο — ο

The formation of hydroperoxides from such highly unsaturated fatty acids as occur in fish oils has also been investigated, but because of the difficulties in the analysis of unstable and complicated reaction products, the investigations have not been brought to such a stage that a conclusion can be drawn of the possible mechanism of the hydroperoxide formation. At present, to the knowledge of this writer, only a few investigations published have a certain connection with the mechanism of hydroperoxide formation from highly unsaturated fatty acids.

One series of investigations has been made by Farmer and his collaborators on the autoxidation of the docosahexaenoate prepared from cod liver oil. In one of their reports, it is indicated that the high rate of oxygen uptake in the autoxidation is due to the fact that the methylene groups located between double bonds in the carbon systems [ — C H = CH—CH 2—] n are particularly liable to oxidation (Farmer and Sutton, 1943b). Later, Farmer et al. (1943) found, by the spectrographic investigation, the development of conjugated unsaturation in the fatty acid chain, and stated that the development of conjugated unsaturation results from the displacement of double bonds and the amount of conjugation is correlated with the degree of peroxidation.

Another investigation has been made by Toyama on the autoxidation of the methyl clupanodonate prepared from sardine oil. Toyama's report (1952) suggests that, in the autoxidation, oxygen not only attacks the unsaturated linkages but also participates in some other reactions, one of which is considered to be the formation of hydroperoxide groups at methylenic carbons and that, in the formation of monomeric oxidation product, the double bonds near the carboxyl group much more readily combine with oxygen, whereas the double bonds remote from the carboxyl group scarcely react with oxygen. Moreover, he has found that

_CH—CHr=CH—

I OOH


conjugated diene content decreases from 13.3 to 10.7% with the increase in oxygen absorption from one mole to two moles per methyl clupano-donate, whereas the peroxide value increases with the oxygen absorption.

Briefly speaking, in the initial stage of autoxidation, oxygen adds at or near the double bonds of the fatty acid chains, to give rise to peroxides; and the process of peroxide formation involves the displacement of double bonds. Moreover, in polyunsaturated fatty acids, conjugated systems are sometimes formed as a result of the displacement of double bonds.

In the later stage, peroxides begin to decompose or react with one another or with other oxidation products. Such reactions result in the formation of various acids, carbonyl compounds, and condensation products. Moreover, near the beginning of the later stage, the development of unpleasant flavor becomes detectable.

The rate of autoxidation of oils is dependent on various factors. One of the factors is the degree of unsaturation. The effect of increasing degree of unsaturation is well manifested in the autoxidation of a series of purified individual fatty acid esters, since in the case of these esters the effects of catalytic substances naturally occurring in oils are eliminated. As the number of isolated double bonds increases, the rate of oxidation increases (Holman and Elmer, 1947).

Temperature is another factor influencing the rate of oxidation; and it is common knowledge that the rate of oxidation increases with increasing temperature. The rise of temperature activates reacting molecules, and at the same time promotes the decomposition of peroxides.

Light and the moisture in oils influence the rate of oxidation. Light accelerates the rate of the formation of peroxides and the rate of decomposition of these compounds; moisture may promote or retard autoxidation, depending on other factors and the amount.

Various substances are known to accelerate the autoxidation of oils. Such substances are called pro-oxidants. Some of the more effective pro-oxidants are various metals, their salts, and metallic soaps. Even if these pro-oxidants are originally not contained in oils, they are frequently formed spontaneously during the storage of oils. For example, metallic soaps may be formed by the reaction between metallic components of the container and the free fatty acids present in small amounts in the oils.

On the other hand, there are certain substances which in small concentrations can retard the autoxidation of oils. Such substances are called


antioxidants. They break the reaction chains by being themselves oxidized, as follows:

ROO · + AH 2 > ROOH + AH · Primary attack (Peroxy radical) (Antioxidant)

2AH · > AH 2 + A Dismutation

ROO · + AH · > ROOH + A Secondary attack

Antioxidants occur naturally in small concentrations in oils, and most of them are phenolic compounds. During the refining of crude oils, the natural antioxidants are often lost; hence such refined oils are more susceptible to autoxidation than crude oils. The deficiency of such refined oils, especially vitamin A oils, is rectified by the addition of commercial antioxidants.

2. Characteristics of Oxidized Fish Oils

The characteristics of oxidized fish oils vary with the degree of oxidation and the factors affecting the autoxidation. In general, the specific gravity, the index of refraction, the viscosity, the acid value, and the saponification value for oxidized fish oils are greater than those for the fresh oils; but the iodine value and the content of ether-insoluble bromides for oxidized fish oils are smaller than for fresh oils. Moreover, oxidized fish oils are characterized by their possession of conjugated acids. Some of the changes in quality can be detected by organoleptic tests.

Oxidized fish oils contain certain amounts of peroxides. However, the peroxide content, or peroxide value as it is called, is not always a measure of the degree of autoxidation; for, at the advanced stage of autoxidation, peroxides undergo decomposition, and correspondingly the peroxide value decreases.

The flavor of oxidized fish oils is different from that of the fresh fish oils, and is unacceptable. So far, inquiries have been made by various investigators into the substances actually responsible for the unpleasant flavor of oxidized fish oils, and a certain amount of information has been obtained.

Davies and Gill (1936) have stated that fishy flavor appears to be associated with traces of peroxides, formaldehyde, and tertiary nitrogen in the form of the volatile base, i.e., trimethylamine, or trimethylamine oxide, or a mixture of both. Also, Broge (1941) and Obata et al (1949)


have reported that, in the autoxidation of fish oils containing small amounts of trimethylamine oxide, a constituent of fish, trimethylamine is formed and contributes to the development of unpleasant flavor.

On the other hand, according to Farmer and Sutton (1943b) , the development of unpleasant fishy flavor in the autoxidation of the fatty acids and their esters prepared from a fish oil appears to be due to the breakdown products of oxidized highly unsaturated acids.

Toyama and Matsumoto (1953) have reported that the volatile substances obtained by an aeration, at 45-55 ° C , of the highly unsaturated fatty acids prepared from sardine oil include various acids and carbonyl compounds which have an unpleasant, sharp odor, but these acids and carbonyl compounds cannot be regarded as the chief substances responsible for the unpleasant odor peculiar to oxidized, highly unsaturated fatty acids.

Besides unpleasant flavor, oxidized fish oils usually have a brown or deep red color, which is quite different from the original. However, the change in color depends on the characteristics of the oils and the degree of oxidation: sometimes, the pigments are bleached by oxidation, with the result that the oils are light-colored, but if such light-colored oils are exposed to air for a prolonged period of time, the color—brown or red— of a different origin develops; sometimes, the brown or red color develops upon autoxidation.

Identification of colored components of oxidized fish oils and the reactions leading to the development of color have been the subjects of some investigators. One group of experiments consisted in examining the effects of various proteins and their decomposition products, and it was found that fish oils, when stored in the presence of proteins and the decomposition products, became red (Otani and Nonaka, 1938; Nonaka and Nishigaki, 1949). Similarly, it has been shown that a fish oil and a protein react to develop a deep brown color (Venolia et al., 1957).

The contribution of trimethylamine to the development of red color has been suggested by Obata and his collaborators (1949) . On the basis of the experiments where fish oils were autoxidized in the presence of trimethylamine, they have formed the idea that the development of red color in fish oils results from the chemical combination of trimethylamine with the aldehydes produced by the decomposition of oxidized highly unsaturated fatty acids (Obata et al., 1952).

On the other hand, according to Nonaka, 1950 and Nonaka et al., 1954, oxidized fatty acids or some compounds formed by the oxidation of un-


saturated fatty acids are precursors of brown-colored components. Colorless or light-colored autoxidized fatty acids change gradually into colored oxidized acids; the development of color is accelerated by various basic compounds (Nonaka, 1950), and may also be accelerated by certain substances other than basic compounds (Nonaka et al., 1954). Moreover, it has been shown that some carbonyl compounds, especially aldehydo acids, formed in the autoxidation of fish oils change into colored compounds of unidentified structure (Nonaka and Komatsu, 1954; Nonaka, 1954, 1956a,b,c).

The relation between the development of color and the content of oxidized fatty acids has been described in two recent reports. In one report, it is shown that, in the autoxidation of fish oils, a remarkable change in color takes place where the content of oxidized fatty acids increases rapidly (Ando, 1954); in the other, it is shown that the color of oxidized fish oils varies from light yellowish brown to dark brown as the content of oxidized fatty acids increases (Matsuhashi, 1954).

3. Vitamin A Content and Fatty Acid Oxidation in Fish Liver Oils

It is a frequent experience that the content of vitamin A in fish liver oils decreases during the storage of the oils. The decrease has been regarded as associated, though not entirely, with the autoxidation of unsaturated fatty acid components of the oils.

It was Fridericia (1924) who as early as 1924 found that when a lard heated in thin layers at 102-105°C. for 24 hr. was added to a butter-fat, the vitamin A in the butterfat was inactivated. He suggested that the inactivation might be due to the formation of peroxides. Later, Pow-ick (1925) found that when rancid lard was mixed with vitamin A-con-taining rations, the lard had the effect of destroying the vitamin A, and stated that the destruction was presumably due to the oxidation of vitamin A by the organic peroxides of the rancid lard. Similarly, it has been found that a decrease in vitamin A content of some liver oils has a relation to the increase in peroxide value (Whipple, 1936; Lowern et al., 1937; Dassow and Stansby, 1949). Moreover, it has been found that, even in the absence of air, the addition of a peroxide-containing oil to a liver oil results in the destruction of vitamin A and that the destruction proceeds at a rate approximately proportional to the peroxide concentration (Smith, 1939).

A systematic investigation has been made by Simons et al. (1940) on the relation between the destruction of vitamin A and the peroxide value


of various liver oils differing in iodine value. The investigation shows that the percentage of vitamin A oxidized at various peroxide values is independent of the initial concentration of the vitamin. Moreover, if the oils are divided into two groups according to unsaturation, it is found that the percentage of vitamin A oxidized at various peroxide values is smaller in the oils with higher unsaturation than in the oils with lower unsaturation and that within each group of oils the percentage of vitamin A oxidized is related to the peroxide value of the oil.

Recently, the relation between the destruction of vitamin A and peroxide formation in unsaturated triglycerides has been investigated by Abe and Ihara (1953) . They added the vitamin A concentrate prepared from cod liver oil to the glycerides, triolein, trilinolein, and trihnolenin, and subjected them to autoxidation at 40° and 80°C. From this experiment, it has been found that, at relatively high rates of autoxidation, the relation between the percentage of vitamin A destroyed and the peroxide value is quite complicated.

4. Antioxidants

The well-known natural antioxidants, tocopherols, occur in small concentrations in various fish oils. Tocopherol contents in various fish oils range from 40 to 628 mg./kg.; for example, 40 in sardine oil, 66 in menhaden oil, 142 in herring oil, and 217 mg./kg. in pink salmon oil (Einset et al, 1957). Moreover, from the data of Einset et al (1957) , the content of tocopherols naturally occurring in fish oils appears to determine the relative stability of the oils against autoxidation.

Certain substances with a function of antioxidants have been examined for use in the retardation of the autoxidation of oils and fats, and it has been found that polyphenols and aromatic amines are the most effective. However, of these compounds, only polyphenols can be used as antioxidants for edible oils and vitamin A oils, since aromatic amines are generally considered too toxic for food use.

For practical use, an antioxidant should be highly effective at low concentrations, accessible at a reasonable price, and easily soluble in oils. It should produce no changes in color and flavor. The antioxidants widely known are butyl hydroxyanisole (BHA) , butyl-hydroxy-toluene ( B H T ) , propylgallate, isoamylgallate, nordihydroguaiaretic acid (NDGA), and resin guaiac.

Besides antioxidants, there are certain substances which are not highly effective by themselves as antioxidants but, when used together


with antioxidants, may increase the effectiveness of the antioxidants. Such substances are called synergists, and some of these are phosphoric acid, citric acid, isopropyl citrate, ascorbic acid, ascorbyl palmitate, and various organic hydroxy acids.

II. Rancidity Problems in Fish

A. INTRODUCTION

Although the term "rancidity" is sometimes mistakenly used to indicate the unpleasant odors absorbed by fatty foods from foreign sources, it denotes the deterioration of flavor and odor of fats or fatty portions of foods. Rancidity results from the chemical deterioration of fats; and the development of rancidity in fish is chiefly due to the oxidative deterioration of the oils. Rancidity is apt to develop in many fatty fishes during storage or handling, since the oils in such fishes are rich in highly unsaturated fatty acids and the highly unsaturated constituents are susceptible to oxidation.

B. DEVELOPMENT OF RANCIDITY

The development of rancidity in fish has been attributed chiefly to the atmospheric oxidation of the fish oils. This process involves the formation and the decomposition of peroxides. The decomposition products include various acids, carbonyl compounds, and condensation products. Some of the acids and carbonyl compounds are said to have an unpleasant flavor or odor. In this respect, the process of oxidation of fish oils in the flesh is similar to the process of autoxidation of extracted oils. However, in other respects, the former differs from the latter. First of all, since the oils are present in the flesh, certain constituents of the flesh participate in, and the flesh itself has some influence on, the oxidation. At present, it is shown that the trimethylamine formed from its oxide during the oxidation greatly contributes to the development of unpleasant odor (see Section I, B , 2 ) .

The effect of herring muscle on the oxidation of extracted herring oil has been investigated under several sets of conditions by Banks (1937) . He found that the herring muscle seemed to catalyze the oxidation of the oil and that this catalytic effect was increased by the presence of sodium chloride but destroyed by heat. From these results, he suggested that the catalytic effect was due to the presence of an oxidative enzyme system. Moreover, in his later reports, it is shown that a fat-oxidizing


enzyme in brown lateral streak of muscle of herring is activated by sodium chloride but unaffected by ammonium sulfate (Banks, 1938b) and that the fat-oxidizing enzyme in herring muscle plays an important role in the development of rancidity and its potency increases as the temperature decreases (Banks, 1939).

The effect of hematin compounds on the oxidation of fish oils and unsaturated fatty acid substrates has been investigated. Banks (1944) has shown that hematin accelerates the oxidation of linoleic acid and of fish liver oils and that the initial stage of the oxidation is not catalyzed by hematin. Brown et al. (1957) have also shown that hematin compounds accelerate the oxidation of ammonium linoleate, of extracted fish oils, and of fish flesh, and that during the oxidation of the oil in fish tissue the hematin compounds are chemically changed and the concentration of the compounds decreases.

Recently, Khan (1952) isolated from the dark muscle of British Columbia herring a highly active enzyme capable of peroxidizing non-conjugated unsaturated fatty acids. This enzyme is a nitrogenous complex having no heavy metals or sulfhydryl group as the active center and can act only in the presence of activators such as certain iron-containing organic nitrogenous compounds, which include hemoglobin and cytochrome c. The enzyme shows its optimal activity at 15°C. and pH 6.9.

C. DETERIORATION OF OILS IN F I S H

A complete picture of the development of rancidity in fish cannot be given within the framework of this review. Basically, the development of rancidity can be attributed to two types of chemical deterioration of the oils. One is the oxidative deterioration, and the other the hydrolytic deterioration; and of these two types, the oxidative deterioration is chiefly responsible for the development of rancidity.

Rancidity in fish becomes apparent in the advanced stages of the chemical deterioration; and then, theoretically, the degree of rancidity increases with the progress of the chemical deterioration. Although it is apparent that rancidity can be detected by organoleptic tests, the determination of the degree of rancidity is, however, difficult and liable to some error, since rancidity does not develop uniformly in all of the fish tested. Non-fatty constituents could obviously also influence taste.

On the other hand, in a series of experiments, the degree of chemical deterioration of oils in fish can be assessed by chemical tests. Therefore, the chemical tests, when combined with the organoleptic assessment of

244 T O M O T A R O T S U C H I Y A

rancidity, are of great assistance where the purpose of investigation is to trace the course of the chemical deterioration and find out the optimum conditions for the storage of fish. However, it is to be noted that the chemical tests alone can hardly give sufficient information as to the degree of rancidity and as to when rancidity develops in fish.

With all these borne in mind, first, the difference between the rate of chemical deterioration of oils in fish and that of extracted fish oils, second, the rate of deterioration of oils in fish under various storage conditions, and third, some of the factors affecting the rate of deterioration will be considered.

The oils in the fish flesh undergo more pronounced and rapid deterioration than extracted oils. For example, in the storage of herring and extracted herring oil at — 2 0 ° C , the peroxide value of the oil present in the fish increases at a greater rate than the value of extracted herring oil (Banks, 1938a). Similarly, in the storage of sardine and extracted sardine oil at —15 ° C , the peroxide value of the oil present in the fish increases more rapidly than the value of extracted sardine oil. Moreover, the acidity of the sardine oil in the fish increases rapidly with the duration of storage, whereas the value of extracted sardine oil scarcely changes (Hashimoto et ah, 1946).

Where fish are stored at room temperature, the oils in the flesh undergo rapid deterioration, the degree of change in the quality increasing with the duration of storage. For example, when pilchards, 4 hr. after their capture, were stored at 20° C. in a dark place, the acidity of the oil became, after a day of storage, 2.5 times the original value (1.06 expressed as oleic acid), after 2 days 7.5 times, and after 5 days 8 times, while the color of the oil changed toward deep red with the duration (Lassen et ah, 1951).

Although fish are stored in ice after their capture until they are brought to the refrigeration storage or subjected to salting, etc., the deterioration in the quality proceeds to a considerable extent depending upon various conditions. Charnley (1945) has examined at intervals the change in acid value of the oil in the flesh of herrings stored at 2-4°C. and shown that the acid value becomes, after 2 days of storage, about twice the value (0.554) in the original fish, after 4 days about 3 times, and after 6 days about 4 times. Therefore, if iced fish are subjected to refrigeration, the duration of ice storage (prestorage period as it is called) determines the life of refrigeration storage during which the frozen fish remain in a favorable state, and the importance of the prestorage period has been emphasized by Dyer (1951) and Banks (1955) .


In the refrigeration storage of fish, the rate of deterioration of the oils decreases roughly with decreasing temperature, though the rate may depend on other factors. The investigation by Banks (1938a) on the temperature effect shows that, in herrings stored at — 2 0 ° C , the peroxide oxygen content (in milliliters of 0.002 Ν thiosulfate per gram) of the oil increased to 2.6 after 14 days of storage, 9.3 after 55 days, 20.4 after 111 days, and 43.7 after 166 days, while in herrings stored at —28 °C. it increased to 2.2 after 14 days, 3.0 after 55 days, 4.5 after 111 days, and 7.6 after 166 days.

Skinning or filleting results in producing the conditions favorable for the penetration of air into the flesh, hence, for the oxidative deterioration of the oils. Thus, in filleted herring, the oxidative deterioration of the oil proceeds at a somewhat greater rate than in the whole herring (Banks, 1952).

Although fish fillets are sometimes lightly brined before subjection to refrigeration in order that dripping may be prevented when the fillets are thawed, this procedure, in turn, leads to the premature development of "salt fish" flavor and rancidity (Tarr, 1944). Similarly, brine-freezing results in producing conditions more favorable to the development of rancidity than air-freezing (Banks, 1938a).

Impurities in the salt for use in salt-curing appear to accelerate the oxidative deterioration of oils in fish flesh. The accelerating effect is illustrated by the experiments on the autoxidation of fats and oils in the presence of commercial dairy salt and of rock salt. The experiments show that the commercial dairy salt prepared from sea water accelerates the oxidation of dry butterfat, lard, beef fat, and some vegetable oils, whereas the salt derived from rock salt has less activity (Hills and Conochie, 1945). The accelerating effect of commercial dairy salt is attributed to the presence of magnesium chloride. This salt appears to act as a heterogeneous catalyst of oxidation. Similarly, the chlorides of calcium, aluminum, zinc, and beryllium are active. Browning in frozen fish and darkening in canning may be attributed to oxidation of the oil constituent (Venolia etat, 1957).

The tocopherol content is an additional important factor in the stability of fish oils. No less than ten different species were studied in this respect as the basis of the extracted oils. Stability was largely proportional to the tocopherol content which ranged from 40 mg./kg. for sardine oil to 630 mg./kg. for sablefish oil. It was roughly inversely proportional to the iodine value (Einset et al., 1957).


D . PRACTICAL MEASURES

Icing, freezing, and salt curing are well-known means of preventing the spoilage of fish during the storage, yet oils in the flesh undergo deterioration to some extent. The deterioration, however, may be retarded by exercising some precautions. Moreover, certain preservatives may be employed.

1. Icing and Freezing

Fish should be iced and placed in a dark place immediately after their capture; and it is desirable to transfer the iced fish as soon as possible to the refrigeration storage at temperatures below —20°C. The shorter the period of ice storage, the more prolonged the keeping quality of frozen fish.

In case fish are filleted, the fillets should be coated with ice glaze. Ice-glazing is an effective way of protecting fish flesh from the penetration of air, hence from oxidative deterioration (Banks, 1938a). Another method, lately attempted, of precluding the effect of atmospheric oxygen in the cold storage of fish is that of filling the storage chamber with carbon dioxide or nitrogen gas. The storage of frozen fish in carbon dioxide or nitrogen gas at 10 cm. Hg pressure has been reported as effective in retarding the autoxidation (Tarr, 1948). However, the storage in carbon dioxide gas is inferior to the storage in nitrogen gas in that the former results in imparting to the fish an undesirable flavor not encountered in the storage in nitrogen gas.

2. Salt Curing

In salt curing, it is important to take into consideration the following factors: ( 1 ) purity of salt; ( 2 ) amount of salt; ( 3 ) duration of initial salting; and ( 4 ) weather conditions. In order to reduce the accessibility of oxygen, fish must be completely covered by the brine.

3. Use of Antioxidants

Recently, the use of antioxidants has been investigated in connection with the cold storage and salt curing of fish; yet it appears to be still in the stage of investigation. Most of the investigations show that the deterioration of oils in frozen or salted fish may be retarded by the application of antioxidants before freezing or salting: for example, in the preparation of frozen and salted fishes, antioxidants may be applied by soaking fish in aqueous solutions containing various antioxidants or by coating


with viscous liquids containing antioxidants; and in the preparation of frozen fish, by coating with ice glaze containing antioxidants.

REFERENCES

Composition of Fish Oils

Adachi, A. (1957a). On the oil of cuttlefish (Ommastrephes sloani pacificus Steestrup). The structure of eicosatrienoic acid. Presented at a meeting of the Chemical Society of Japan, Tokyo, 1957.

Adachi, A. (1957b). On the oil of cuttlefish (Ommastrephes sloani pacificus Steestrup). The structure of docosatrienoic acid. Presented at a meeting of the Chemical Society of Japan, Tokyo, 1957.

Adachi, A. (1957c) . On the oil of cuttlefish (Ommastrephes sloani pacificus Steestrup). The structure of docosatetraenoic acid. Presented at a meeting of the Chemical Society of Japan, Tokyo, 1957.

Arcus, C. L., and Smedley-Maclean, I. (1943) . The structure of arachidonic and linoleic acids. Biochem. J. 37, 1-6.

Armstrong, E. F. , and Hilditch, T. P. (1925) . The constitution of natural unsaturated fatty acids. II. Some acids present in a South Georgia whale oil. /. Soc. Chem. Ind. (London) 44, 180-189T.

Bailey, Β. E. (1938) . Fish oils. VII. The pigments of pilchard oil. J. Fisheries Research Board Can. 4, 55-58 (1938) . Chem. Abstr. 32, 5650.

Baldwin, W. H., and Parks, L. E. (1943) . The body oil from menhaden (Bre-voortia tyrannus). Oil & Soap 20, 101-104.

Baudart, P. (1943a). The polyethylenic fatty acids from the liver of Carcharodon carcharias. V. Separation and constitution of eicosatrienoic and docosatrienoic acids. Bull. soc. chim. (France) 10, 440-443; (1944) . Chem. Abstr. 38, 6274.

Baudart, P. (1943b). The polyethylenic fatty acids from the liver of Carcharodon carcharias. VI. Separation and constitution of docosatetraenoic acid. Bull. soc. chim. (France) 10, 443-445; (1944) . Chem. Abstr. 38, 6274.

Bjarnason, Ο. B., and Meara, M. L. (1944) . The mixed unsaturated glycerides of liquid fats. V. Low-temperature crystallization of Icelandic herring oil. /. Soc. Chem. Ind. (London) 63, 61-63.

Bull, H. (1906) . Über die Trennung der Fettsäuren des Dorschleberöls. Ber deut. chem. Ges. 39, 3570-3576.

Davies, W. H., Heilbron, I. M., and Jones, W. E. (1933) . The unsaponifiable matter from the oil of elasmobranch fish. IX. The structure of batyl and selachyl alcohols. J. Chem. Soc. (London) 1933, 165-167.

Drummond, J . C , Singer, E. , and MacWalter, R. J . (1935) . A study of the unsaponifiable fraction of wheat germ oil with special reference to vitamin E . Biochem. J. 29, 456-471.

Harper, D. Α., and Hilditch, T. P. (1937) . The component acids and glycerides of partly-hydrogenated marine animal oil. / . Soc. Chem. Ind. (London) 56, 322-329T.

Hata, C , and Kunisaki, T. (1942a). Studies on the fish oil and liver oil of West-southern Pacific Ocean. IV. On the liver oil of Scoliodon walbeehmi, Bleeker ( 1 ) . / . Chem. Soc. Japan 63, 1585-1590.


Hata, C , and Kunisaki, T. (1942b). Studies on the fish oil and liver oil of Western-southern Pacific Ocean. V. On the liver oil of Scoliodon walbeehmi Bleeker. / . Chem. Soc. Japan 63, 1591-1595.

Heilbron, I. M., and Owens, W. M. (1928) . The unsaponifiable matter from the oil of elasmobranch fish. IV. The establishment of the structure of selachyl and batyl alcohols as monoglyceryl ethers. J. Chem. Soc. (London) 1928, 942-947.

Heilbron, I. Μ., Kamm, Ε. D., and Owens, W. M. (1926) . The unsaponifiable matter from the oils of elasmobranch fish. I. A contribution to the study of the constitution of squalene (spinacene). / . Chem. Soc. (London) 1926, 1630-1644.

Hilditch, T. P., and Lovern, J. A. (1928) . The head and blubber oils of the sperm whale. I. Quantitative determinations of the mixed fatty acids present. /. Soc. Chem. Ind. (London) 47, 105-111T.

Hof Städter, P. G. (1854) . Untersuchung des Fettes des Kopfes des Pottwals (Physeter macrocephalus Shaw). Ann. Chem. Liebigs 91, 177-185.

Ikuta, H., and Ueno, S. (1930) . Composition of the saturated fatty acids of Japanese sardine oil. (In Japanese.) J. Soc. Chem. Ind. Japan 33, 720-725.

Karrer, P., and Helfenstein, A. (1931) . Synthese des Squalens. Helv. Chim. Acta 14, 78-85.

Kimura, K. (1926) . Ingwandarame oil. (In Japanese.) / . Soc. Chem. Ind. Japan 29, 620-623.

Kino, K. (1934) . C2 2-acids of sardine oil. / . Soc. Chem. Ind. Japan 37, 1006-1010. Klenk, E. (1927) . Nervon-säure. Ζ. physiol. Chem. 166, 287-293. Komori, S., and Agawa, T. (1954) . On the liver oil of Laemonema morosum

Matsubara. II. On the research of the docosenol fractions. / . Chem. Soc. Japan 75, 1051-1054.

Komori, S., Agawa, T., Hirao, T., and Kumata, K. (1956) . On the liver oil of Laemonema morosum Matsubara. III. On the components of low-boiling fractions of unsaponifiable matter. (In Japanese.) Abura Kagaku 5, 284-287.

Lederer, E. , and Pliva, T. (1951) . Sur le pristane de l'ambre gris. Bull. soc. chim. (France) 1951, 72-73.

Lovern, J . A. (1932) . General survey of the fatty acid composition of the fats of a number of fishes, both marine and freshwater. Biochem. J. 26, 1978-1984.

Lovern, J . A. (1934a). Fat metabolism in fishes. IV. Mobilization of depot fat in the salmon. Biochem. J. 28, 1955-1960.

Lovern, J . A. (1934b). Fat metabolism in fishes. V. The fat of the salmon in its young freshwater stages. Biochem. J. 28, 1961-1963.

Matic, M. (1958) . South African pilchard oil. 7. The isolation and structure of an octadecatetraenoic acid from South African pilchard oil. Biochem. J. 68, 692-695.

Matsuda, S. (1942a). On studies of highly unsaturated acids. I. The chemical constitution of C 1 6H 2 60 2 in bonito oil. / . Soc. Chem. Ind. Japan 45, 8-11.

Matsuda, S. (1942b). On studies of highly unsaturated acids. II. The chemical constitution of C 1 8H 2 80 2 in bonito oil. J . Soc. Chem. Ind. Japan 45, 11-15.

Matsuda, S. (1942c) . On studies of highly unsaturated acids. IV. The chemical constitution of eicosatetraenoic acid, C 2 0H 3 2O 2, in bonito oil. J . Soc. Chem. Ind. Japan 45, 17-18.


Matsuda, S. (1942d). On studies of highly unsaturated acids. V. The chemical constitution of C 2 0H 3 0O 2 in bonito oil. / . Soc. Chem. Ind. Japan 45, 144-147.

Matsuda, S. (1942e). On studies of highly unsaturated acids. VI. The separation of C2 2-highly unsaturated acid, C 2 2H 3 40 2 and C 2 2H 3 20 2 , in bonito oil. J . Soc. Chem. Ind. Japan 45, 247-249.

Matsuda, S. (1942f). On studies of highly unsaturated acids. IX. The chemical constitution of C 2 2H 3 20 2 in bonito oil. / . Soc. Chem. Ind. Japan 45, 409-412.

Matsuda, S. (1942g). On studies of highly unsaturated acids. X. The chemical constitution of C 2 4H 3 40 4 in bonito oil. / . Soc. Chem. Ind. Japan 45, 412-416.

Matsuda, S., and Ueno, S. (1938) . Studies on bonito oil. III. J. Chem. Soc. Japan 59, 1061-1065.

Matsuda, S., and Ueno, S. (1939) . Studies on bonito oil. IV. Liquid fatty acids ( 2 ) . / . Chem. Soc. Japan 60, 49-55.

Matsumoto, T., Sone, H., and Niiya, I. (1955) . On the lipid of Xenogramma carinatum Weite. (In Japanese.) / . Oil Chemists' Soc. (Japan) 4, 131-133.

Morice, I. M., and Shorland, F . B. (1955) . The isolation of n-pentadecanoic and n-heptadecanoic acids from shark (Galeorhinus australis Macleay) liver oils. Biochem. J. 61, 453-456.

Nakamiya, J . (1935) . Gadusene, an unsaturated hydrocarbon occurring in animal and vegetable oils. Sei. Papers Inst. Phys. Chem. Research (Tokyo) 28, 16-26.

Nakamiya, J . , and Kawakami, K. (1927) . On the hydrogenation of biosterin. Set. Papers Inst. Phys. Chem. Research (Tokyo) 7, 121-142.

Nobori, H. (1940a). On the constituents of lower saturated fatty acids in Japanese sardine oil. (In Japanese; English summary in Suppl.) J. Soc. Chem. Ind. Japan 43, 128-130.

Nobori, H. (1940b). On the lower saturated fatty acids in herring oil. (In Japanese; English summary in Suppl.) / . Soc. Chem. Ind. Japan 43, 250-252.

Ono, T. (1932) . On a shark egg-oil. (In Japanese.) J . Agr. Chem. Soc. Japan 8, 788-795.

Shimo-oka, T., and Toyama, Y. (1954) . Separation and structure determination of eicosatetraenoic acid in ox liver lipid. (In Japanese.) J . Oil Chemists' Soc. (Japan) 3, 161-163.

Shimo-oka, T., and Toyama, Y. (1955) . Separation and structure determination of eicosatetraenoic acid in swine liver lipid. (In Japanese.) / . Oil Chemists' Soc. (Japan) 4, 27-29.

Silk, Μ. H., and Hahn, Η. Η. (1954) . South African pilchard oil. IV. The isolation and structure of a hexadecatetraenoic acid from South African pilchard oil. Biochem. J. 57, 582-587.

Sörensen, J. S., and Sörensen, Ν. Α. (1949) . Studies related to pristane. III. The identity of norphytane and pristane. Acta Chem. Scand. 3, 939-945.

Sörensen, Ν. Α. (1935) . Lipochromes of marine animals. VI. The carotenoids of salmon flesh. Z. physiol. Chem. 235, 8-11; (1935) . Chem. Abstr. 29, 6615.

Suzuki, B. (1929a). On the separation of glycerides. VI-IX. Proc. Imp. Acad. (Tokyo) 5, 266-268.

Suzuki, B. (1929b). On the separation of glycerides. X-XIV. Proc. Imp. Acad. (Tokyo) 5, 269-271.


Suzuki, B., and Masuda, Y. (1928) . On the separation of glycerides. V. Cod liver oil. Proc. Imp. Acad. (Tokyo) 4, 165-168.

Takano, M. (1933) . Chemical constitution of the unsaturated fatty acid, C 2 0H 3 8O 2, in Japanese sardine oil. (In Japanese; English summary in Suppl.) /. Soc. Chem. Ind. Japan 36, 1317-1319.

Takao, M., and Tomiyama, S. (1954) . Studies on the constituents and utilization of cuttlefish oil. IV. Studies on the new glyceride, myristopalmitostearin. /. Agr. Chem. Soc. Japan 28, 333-335.

Toyama, Y. (1923) . Notes on salmon and trout oils. / . Soc. Chem. Ind. Japan 26, 597-604.

Toyama, Y. (1925a). On the composition of the fatty acids of whale oils. I. Fatty acids of humpback whale. / . Soc. Chem. Ind. Japan 28, 95-103.

Toyama, Y. (1925b). On the composition of fatty acids of whale oils. II. The fatty acids of finback whale oil. / . Soc. Chem. Ind. Japan 28, 104-108.

Toyama, Y. (1925c) . On the occurrence of a saturated hydrocarbon in shark liver oils. (In Japanese.) Repts. Govt. Chem. Ind. Research Inst. Tokyo 20 (2 ) , 119-154.

Toyama, Y. (1925d). On the unsaponifiable matter (higher alcohols) of shark and ray liver oils. III. (In Japanese.) Repts. Govt. Chem. Ind. Research Inst. Tokyo 20 (2 ) , 155-178.

Toyama, Y. (1925e). On the unsaponifiable matter (higher alcohols) of shark and ray liver oils. IV. (In Japanese.) Repts. Govt. Chem. Ind. Research Inst. Tokyo 20(2) , 179-188.

Toyama, Y. (1925f). On the unsaponifiable matter (higher alcohols) of shark and ray liver oils. V. (In Japanese.) Repts. Govt. Chem. Ind. Research Inst. Tokyo 20 (2 ) , 189-200.

Toyama, Y. (1925g). On oleyl alcohol. (In Japanese.) Repts. Govt. Chem. Ind. Research Inst. Tokyo 20 (2 ) , 201-213.

Toyama, Y. (1926a). On the composition of fatty acids of whale oils. III. The fatty acids of sei whale oil. / . Soc. Chem. Ind. Japan 29, 531-538.

Toyama, Y. (1926b). On the composition of fatty acids of whale oils. IV. The fatty acids of California gray whale oil. /. Soc. Chem. Ind. Japan 29, 538-546.

Toyama, Y. (1926c) . On the fatty acids of cod liver oil. J. Soc. Chem. Ind. Japan 29, 624-630.

Toyama, Y. (1927a). Composition of the body oil from sperm whale. I. Fatty acids. (In Japanese.) / . Soc. Chem. Ind. Japan 30, 519-527.

Toyama, Y. (1927b). On the chemical constitution of cetoleic acid. / . Soc. Chem. Ind. Japan 30, 597-602.

Toyama, Y. (1927c) . On the chemical constitution of zoomaric acid. J. Soc. Chem. Ind. Japan 30, 603-607.

Toyama, Y., and Ishikawa, T. (1934a). Identification of gadoleic acid in sei whale and humpback whale oil. / . Soc. Chem. Ind. Japan 37, 1179-1181.

Toyama, Y., and Ishikawa, T. (1934b). A new eicosenoic acid in pilot whale oil. / . Soc. Chem. Ind. Japan 37, 1181-1182.

Toyama, Y., and Ishikawa, T. (1938) . The unsaponifiable matter of the liver oil of Squalus suckleyi. J. Chem. Soc. Japan 59, 1367-1374.


Toyama, Y., and Takahashi, M. (1939) . The highly unsaturated alcohols in the liver oil of Squalus suckleyi. J. Chem. Soc. Japan 60, 1177-1180.

Toyama, Y., and Tsuchiya, T. (1927a). On the fatty acids of shark and ray liver oils. III. The fatty acids of yamato-torpedo liver oil. J. Soc. Chem. Ind. Japan 30, 63-70.

Toyama, Y., and Tsuchiya, T. (1927b). On the fatty acids of shark and ray liver oils. IV. The fatty acids of kokonohoshiginzame liver oil. J . Soc. Chem. Ind. Japan 30, 116-122.

Toyama, Y., and Tsuchiya, T. (1927c) . On the fatty acids of shark and ray liver oil. V. The fatty acids of aburatsunozame liver oil. J . Soc. Chem. Ind. Japan 30, 207-215.

Toyama, Y., and Tsuchiya, T. (1929a). Über die hochungesättigten Säuren des Sardinenöls. I. Mitteilung: eine neue Säure, C 1 6H 2 60 2 , und die hochungesättigten C1 8-Säuren. Bull. Chem. Soc. Japan 4, 83-91.

Toyama, Y., and Tsuchiya, T. (1929b). Distillates from hydrogenated fish and sperm oils during vacuum deodorization process. J. Soc. Chem. Ind. Japan 32, 1165-1171.

Toyama, Y., and Tsuchiya, T. (1934a). Gadoleic acid in cod liver oil. / . Soc. Chem. Ind. Japan 37, 31-34.

Toyama, Y., and Tsuchiya, T. (1934b). Identification of gadoleic acid in Japanese sardine oil, herring oil, and liver oil of sukeso-dara (Theragra chalcogramma). J. Soc. Chem. Ind. Japan 37, 34-37.

Toyama, Y., and Tsuchiya, T. (1934c) . Highly unsaturated C2 4-acids in herring, cod liver, pilot whale, and aburazame liver oils. J. Soc. Chem. Ind. Japan 37, 1176-1179.

Toyama, Y., and Tsuchiya, T. (1935a). Occurrence of a saturated hydrocarbon, pristane, in sardine, herring and sperm whale oils. J . Soc. Chem. Ind. Japan 38, 627-631.

Toyama, Y., and Tsuchiya, T. (1935b). Separation of physeteric acid from sardine and pilot whale oils. / . Soc. Chem. Ind. Japan 38, 1484-1487.

Toyama, Y., and Tsuchiya, T. (1935c) . Separation of selacholeic acid from cod liver, sukeso-dara liver, sei whale, and pilot whale oils. / . Soc. Chem. Ind. Japan 38, 1487-1489.

Toyama, Y., and Tsuchiya, T. (1935d). The highly unsaturated acids in sardine oil. II. The constitution of hiragonic acid, C 1 6H 2 60 2 . Bull. Chem. Soc. Japan 10, 192-199.

Toyama, Y., and Tsuchiya, T. (1935e). The highly unsaturated acids in sardine 011. III. The isolation and constitution of moroctic acid, C 1 8H 2 80 2 . Bull. Chem. Soc. Japan 10, 232-241.

Toyama, Y., and Tsuchiya, T. (1935f). The highly unsaturated acids in sardine oil. V. The constitution of eicosatetraenoic acid, C 2 0H 3 2O 2. Bull. Chem. Soc. Japan 10, 296-300.

Toyama, Y., and Tsuchiya, T. (1935g). The highly unsaturated acids in sardine oil. VI. The constitution of eicosapentaenoic acids, C 2 0H 3 0O 2. Bull. Chem. Soc. Japan 10, 301-304.

Toyama, Y., and Tsuchiya, T. (1935h). The highly unsaturated acids in sardine oil. VIII. The constitution of clupanodonic acid, C 2 2H 3 40 2 . Bull. Chem. Soc. Japan 10, 441-453.


Toyama, Y., and Tsuchiya, T. (1935i). The highly unsaturated acids in sardine oil. IX. The constitution of docosahexaenoic acid, C 2 2H 3 20 2 . Bull. Chem. Soc. Japan 10, 539-543.

Toyama, Y., and Tsuchiya, T. (1935j). The highly unsaturated acids in sardine oil. X. The separation of highly unsaturated C2 4-acids. Bull. Chem. Soc. Japan 10, 543-547.

Toyama, Y., and Tsuchiya, T. (1935k). The highly unsaturated acids in sardine oil. XI. The constitution of nisinic acid, C 2 4H 3 60 2 in sardine oil. Bull. Chem. Soc. Japan 10, 547-551.

Toyama, Y., and Tsuchiya, T. (19351). Tetradecenoic and dodecenoic acids in sperm whale oil. I. Tetradecenoic and dodecenoic acids in sperm blubber oil. J. Chem. Soc. Japan 56, 1050-1054.

Toyama, Y., and Tsuchiya, T. (1935m). Tetradecenoic and dodecenoic acids in sperm oil. II. Dodecenoic acid in sperm head oil. J. Chem. Soc. Japan 56, 1055-1057.

Toyama, Y., and Tsuchiya, Τ. (1935n). Decenoic acid C 1 0H 1 8O 2 in head oil of sperm whale. / . Chem. Soc. Japan 56, 1313-1315.

Toyama, Y., and Yamamoto, T. (1953a). The highly unsaturated acids in sardine oil. XVI. The structure of hexadecatetraenoic and octadecatrienoic acids. (In Japanese.) /. Oil Chemists' Soc. (Japan) 2, 147-149.

Toyama, Y., and Yamamoto, T. (1953b). The highly unsaturated acids in sardine oil. XVII. Re-examination of the structure of eicosatetraenoic acid. / . Oil Chemists Soc. (Japan) 2, 193-194.

Tsuchiya, T. (1932) . High molecular solid fatty acids in sardine oil. (In Japanese.) Repts. Govt. Chem. Ind. Research Inst. Tokyo 27 (2 ) , 75-78.

Tsuchiya, T. (1940) . Studies on highly unsaturated acid. II. Occurrence of a new highly unsaturated acid, C 1 6H 2 40 2 , in sardine oil. / . Chem. Soc. Japan 61, 1188-1191.

Tsuchiya, T. (1941) . Studies on highly unsaturated acids. III. The constitution of a new highly unsaturated acid, C 1 6H 2 40 2 , in sardine oil. / . Chem. Soc. Japan 62, 10-12.

Tsuchiya, T. (1942a). Studies on highly unsaturated acids. V. The constitution of octadecatrienoic acid, C 1 8H 3 0O 2, in sardine oil. / . Chem. Soc. Japan 63, 650-653.

Tsuchiya, T. (1942b). Studies on highly unsaturated acids. VII. A solid glyceride containing highly unsaturated acid radical in sardine oil. /. Chem. Soc. Japan 63, 1727-1730.

Tsuchiya, T. (1949) . Studies on highly unsaturated acids. XIII. The separation of docosatetraenoic acid, C 2 2H 3 60 2 , from sardine oil. (In Japanese.) Repts. Govt. Chem. Ind. Research Inst. Tokyo 44 (2 ) , 121-125.

Tsuchiya, T. (1951a). On the eicosenoic acid in dolphin oil. / . Soc. Chem. Ind. Japan 54, 672-673.

Tsuchiya, T. (1951b). Unpublished. Tsuchiya, T. (1952) . On a highly unsaturated hydrocarbon of fatty matter of

sperm whale liver. / . Soc. Chem. Ind. Japan 55, 312-313. Tsuchiya, T., and Kato, A. (1950) . On a highly unsaturated hydrocarbon of fatty

matter of finback whale liver. / . Chem. Soc. Japan 71, 514-515.


Tsuchiya, T., and Kaneko, R. (1954) . Investigation of oils and fats in Japan. VI. On their ultraviolet absorption spectra. (In Japanese with English summary.) Repts. Govt. Chem. Ind. Research Inst. Tokyo 49, 273-277.

Tsuchiya, T., and Mamuro, H. (1958) . On the unsaponifiable matter of fatty substance of pilot-whale liver. Presented at a meeting of the Chemical Society of Japan, Tokyo, 1958.

Tsuchiya, T., and Tanaka, A. (1957) . The unsaponifiable matter of ishinagi and tunny liver oils. (In Japanese with English summary.) Repts. Govt. Chem. Ind. Research Inst. Tokyo 52, 269-274.

Tsuchiya, T., and Tanaka, A. (1958) . On the unsaponifiable matter of fatty substance of sei whale liver. Presented at a meeting of the Chemical Society of Japan, Tokyo, 1958.

Tsuchiya, T., Kaneko, R., and Endo, Τ. (1952) . On the chemical constitution of pristane. I. / . Soc. Chem. Ind. Japan 55, 249-251.

Tsujimoto, M. (1906) . On the liver oil of kurokozame (Centroscyllium ritten Jordan & Fowler). / . Soc. Chem. Ind. Japan 9, 953-958.

Tsujimoto, M. (1916) . On an unsaturated hydrocarbon in shark liver oil. /. Soc. Chem. Ind. Japan 19, 277-280.

Tsujimoto, M. (1917a). On the saturated hydrocarbon in basking shark oil. (In Japanese.) Repts. Govt. Chem. Ind. Research Inst. Tokyo 12(10) , 135-138.

Tsujimoto, M. (1917b). Some fresh-water fish oils (carp oil, loach oil, and trout oil). / . Soc. Chem. Ind. Japan 20, 711-719.

Tsujimoto, M. (1917c) . A highly unsaturated hydrocarbon in shark oils. I. /. Soc. Chem. Ind. Japan 20, 953-1017.

Tsujimoto, M. (1918) . On shark and ray liver oils. J. Soc. Chem. Ind. Japan 21, 1015-1040.

Tsujimoto, M. (1920) . Squalene, a highly unsaturated hydrocarbon in shark liver oil. Ind. Eng. Chem. 12, 63-72.

Tsujimoto, M. (1923) . On a new unsaturated fatty acid in sperm whale and dolphin oils. (In Japanese.) / . Soc. Chem. Ind. Japan 26, 608-620.

Tsujimoto, M. (1925) . On the fatty acids of shark and ray liver oil. I. On new fatty acids in shark liver oil. / . Soc. Chem. Ind. Japan 28, 835-842.

Tsujimoto, M. (1926a). On the fatty acids of shark and ray liver oils. II. On the fatty acids of aizame liver oil. / . Soc. Chem. Ind. Japan 29, 67-71.

Tsujimoto, M. (1926b). On the composition of herring oil. I. Saturated acids and acids of the oleic series of ö-nishin oil (great herring oil). J. Soc. Chem. Ind. Japan 29, 195-202.

Tsujimoto, M. (1927a). On aburagarei oil of Hokkaido. J . Soc. Chem. Ind. Japan 30, 402-404.

Tsujimoto, M. (1927b). On the chemical constitution of selacholeic acid. /. Soc. Chem. Ind. Japan 30, 868-873.

Tsujimoto, M. (1930a). The fatty substance of finback whale liver. (In Japanese.) Repts. Govt. Chem. Ind. Research Inst. Tokyo 25 (4 ) , 51-59.

Tsujimoto, M. (1930b). On the unsaponifiable matter in cuttlefish oil. (In Japanese.) Repts. Govt. Chem. Ind. Research Inst. Tokyo 25 (4 ) , 61-70.

Tsujimoto, M. (1931) . On the occurrence of a hydrocarbon in ishinagi liver oil. Bull. Chem. Soc. Japan 6, 237-239.


Tsujimoto, M. (1932a). On the oils of liver, body, viscera and egg of Squalus suckleyi Girard and Centroscyllium ntteri Jordan & Fowler. (In Japanese.) Repts. Govt. Chem. Ind. Research Inst. Tokyo 27(15) , 15-35.

Tsujimoto, M. (1932b). On the liver and body oils of Stereolepis ischinagi Hilgendorf. (In Japanese.) Repts. Govt. Chem. Ind. Research Inst. Tokyo 27(15) , 35-46.

Tsujimoto, M. (1932c) . Seven kinds of fresh-water fish oil (oils of carp, goldfish, trout (Pleeoglossus altivelis), Hypomesus olidus, Charr, Oncorhynchus macrosto-mus Günther, Parasilurus asotus L.) (In Japanese.) Repts. Govt. Chem. Ind. Research Inst. Tokyo 27(15) , 55-60.

Tsujimoto, M. (1935a). On basking shark liver oil. Bull. Chem. Soc. Japan 10, 144-148.

Tsujimoto, M. (1935b). On a new hydrocarbon in basking shark liver oil. Bull. Chem. Soc. Japan 10, 149-153.

Tsujimoto, M. (1936) . "Kan-yu no Kenkyu," pp. 184-412. Maruzen, Tokyo. (Translated title: "Studies on Liver Oils.")

Tsujimoto, M., and Kimura, K. (1927) . On the fatty substance of sperm whale liver. (In Japanese.) Repts. Govt. Chem. Ind. Research Inst. Tokyo 22(12) , 53-63.

Tsujimoto, M., and Toyama, Y. (1922) . On the unsaponifiable matter (higher alcohol) in shark and ray liver oils. (In Japanese.) / . Soc. Chem. Ind. Japan 25, 1-12.

Ueno, S., and Iwai, M. (1934) . On the chemical composition of hiragashira liver 011. Especially, on a new highly unsaturated fatty acid, C 2 4 H 3 80 2. (In Japanese.) J. Soc. Chem. Ind. Japan 37, 562-568.

Ueno, S., and Komori, S. (1935a). The composition of itoyo fish oil. / . Soc. Chem. Ind. Japan 38, 825-831.

Ueno, S., and Komori, S. (1935b). On the unsaponifiable matter of Alaska pollack liver oil and the unsaponifiable matter and solid acids of plaice (Cynopsetta duhbia Schmidt) oil. (In Japanese.) J. Soc. Chem. Ind. Japan 38, 831-835.

Ueno, S., and Matsushima, K. (1957) . On the occurrence of highly unsaturated and monoenoic, dienoic, and trienoic unsaturated alcohols in Laemonema morosum liver oil. (In Japanese.) Abura Kagaku 6, 222-225.

Ueno, S., and Yonese, T. (1936a). On a new highly unsaturated acid, C 2 6H 4 0O 2, in Tunny oil. / . Chem. Soc. Japan 57, 180-183.

Ueno, S., and Yonese, T. (1936b). Investigation of highly unsaturated fatty acids in tunny oil. / . Chem. Soc. Japan 57, 322-325.

Ueno, S., Yamashita, M., and Ota, Y. (1928) . On the vitamin A content of unsaponifiable matter of liver oils. I. (In Japanese.) / . Soc. Chem. Ind. Japan 31, 1198-1206.

Von Weber, U. (1939) . Die Bestimmung des Verzweigungsgrades von Gemischen der Paraffinkohlenwasserstoffe. Angew. Chem. 52, 607-610.

Whitcutt, J . Μ., and Sutton, D. A. (1956) . South African pilchard oil. 5. The isolation and structure of an eicosapentaenoic acid from South African pilchard oil. Biochem. J. 63, 469-475.


Seasonal Variation and Others

Black, Μ. M., and Schwartz, Η. M. (1950) . South African fish products. XXX. Seasonal changes in the composition of the pilchard (Sardina oceUata Jenyns). /. Sei. Food Agr. 1, 182-185.

Higashi, H., Kaneko, T., and Sugii, K. (1953a). Studies on utilization of the liver oil of deep sea sharks. IV. Hydrocarbon contents in yume-zame (Centro-scymus owstoni Garman). (In Japanese with English summary.) Bull. Japan. Soc. Sei. Fisheries 19, 836-850.

Higashi, H., Kaneko, T., and Sugii, K. (1953b). Studies on utilization of the liver oil of deep sea sharks. V. Hydrocarbon contents in heratsuno-zame (Deania spp.) (In Japanese with English summary.) Bull. Japan. Soc. Set. Fisheries 19, 851-860.

Lovern, J . A. (1938) . Fat metabolism in fishes. XII. Seasonal changes in the composition of herring fat. Biochem. J. 32, 676-680.

Shorland, F . B. (1953) . New Zealand fish oils. 6. Seasonal variation in the composition of New Zealand groper (Polyprion oxygeneios) liver oil. Biochem. J. 54, 673-677.

Wada, M. (1955) . Biochemical studies on the fat of the sardine body. III. On the seasonal variation in the fat content in different tissues of male and female sardine fish (In Japanese with English summary.) / . Agr. Chem. Soc. Japan 29, 465-471.

Zama, K., and Ichinoe, H. (1951) . Studies on fats of spring herring. (In Japanese with English summary.) Bull. Japan. Soc. Set. Fisheries 17, 57-59.

Oxidation of Fish Oils

Abe, Y., and Ihara, T. (1953) . The stability of fish liver oil. IV. The relation between vitamin A destruction and peroxide formation in olein, linolein, and linolenin. (In Japanese with English summary.) Bull. Japan. Soc. Set. Fisheries 19, 95-98.

Ando, K. (1954) . Some properties of oxidizing fish oil concerning to its condition of oxidation. (In Japanese with English summary.) Bull. Japan. Soc. Sei. Fisheries 19, 1069-1071.

Broge, J . A. (1941) . Über Geruch und Geschmack von Heringsöl. Fette u. Seifen 48, 188-189.

Dassow, J . Α., and Stansby, Μ. E. (1949) . Stabilization of vitamin A in halibut liver oil with nordihydroguaiaretic acid (NDGA). / . Am. Oil Chemists' Soc. 26, 475-481.

Davies, W. L., and Gill, E . (1936) . Investigations on fish flavor. J. Soc. Chem. Ind. (London) 55, 141-146T.

Einset, E. , Olcott, H. S., and Stansby, Μ. E. (1957) . Oxidative deterioration in fish and fishery products. IV. Progress on studies concerning oxidation of extracted oils. Com. Fisheries Rev. 19(5a) , 35-37.

Farmer, Ε. H., and Sutton, D. A. (1943a). The course of autoxidation reactions in polyisoprenes and allied compounds. IV. The isolation and constitution of photochemically-formed methyl oleated peroxide. / . Chem. Soc. (London) 1943, 119-122.


Farmer, Ε. H., and Sutton, D. A. (1943b). The course of autoxidation reactions in polyisoprenes and allied compounds. V. Observations on fish-oil acids. /. Chem. Soc. (London) 1943, 122-125.

Farmer, Ε. H., Koch, H. P., and Sutton, D. A. (1943) . The course of autoxidation reactions in polyisoprenes and allied compounds. VII. Rearrangement of double bonds during autoxidation. J . Chem. Soc. (London) 1943, 541-547.

Fridericia, L. S. (1924) . Inactivating action of some fats on vitamin A in other fats. / . Biol. Chem. €2, 471-485; (1925) . Chem. Abstr. 19, 851.

Gunstone, F . D., and Hilditch, T. P. (1946) . The autoxidation of methyl oleate in presence of small proportions of methyl linoleate. J . Chem. Soc. (London) 1946, 1022-1025.

Holman, R. T. (1954) . Autoxidation of fats and related substances. In "Progress in the Chemistry of Fats and Other Lipids" (R. T. Holman, W. O. Lundberg, and T. Malkin, eds.), Vol. 2, pp. 51-98. Pergamon, New York.

Holman, R. T., and Elmer, O. C. (1947) . The rate of oxidation of unsaturated fatty acids and esters. J . Am. Oil Chemists' Soc. 24, 127-129.

Lowern, L., Anderson, L., and Harrison, R. W. (1937) . Cereal flours as antioxidants for fishery products. Halibut liver and salmon oils. Ind. Eng. Chem. 29, 151-156.

Matsuhashi, T. (1954) . Studies in preventing the oxidation of fish oils and fish products. II. The significance of oxidized acid in the problem of fish oil deterioration. (In Japanese with English summary.) Bull. Japan. Soc. Sei. Fisheries 20, 497-500.

Nonaka, J . (1950) . Studies on a kind of discoloration of fish-oil. IV. (In Japanese.) Bull. Japan. Soc. Sei. Fisheries 16, 299-302.

Nonaka, J . (1954) . Studies on a kind of discoloration of fish-oil. X. (In Japanese with English summary.) Bull. Japan. Soc. Set. Fisheries 20, 319-322.

Nonaka, J . (1956a). Studies on a kind of discoloration of fish-oil. XI. (In Japanese with English summary.) Bull. Japan. Soc. Sei. Fisheries 21, 1244-1247.

Nonaka, J . (1956b). Studies on a kind of discoloration of fish-oil. XII. (In Japanese with English summary.) Bull. Japan. Soc. Set. Fisheries 21, 1248-1249.

Nonaka, J . (1956c) . Studies on a kind of discoloration of fish-oil. XIII. (In Japanese with English summary.) Bull. Japan. Soc. Set. Fisheries 21, 1250-1252.

Nonaka, J . , and Nishigaki, K. (1949) . Studies on a kind of discoloration of fish-oil. I. (In Japanese with English summary.) Bull. Japan. Soc. Sei. Fisheries 15, 267-269.

Nonaka, J . , and Komatsu, Μ. (1954) . Studies on a kind of discoloration of fish-oil. IX. (In Japanese with English summary.) Bull. Japan. Soc. Set. Fisheries 20, 46-49.

Nonaka, J . , Ando, K., and Komatsu, M. (1954) . Studies on a kind of discoloration of fish-oil. VIII. (In Japanese with English summary.) Bull. Japan. Soc. Set. Fisheries 20, 40-45.

Obata, Y., Hoshi, K., and Matsuno, K. (1949) . Chemical studies on the substances of fish smell. I. Substances concerned with fishy smell and natural coloration of fish oil. (In Japanese with English summary.) Bull. Japan. Soc. Set. Fisheries 15, 412-414.


Obata, Y., Igarashi, H., Zama, K., and Narita, S. (1952) . Mechanism of discoloration of fish-oils. (In Japanese with English summary.) Bull. Japan. Soc. Sei. Fisheries 17, 349-352.

Otani, T., and Nonaka, J . (1938) . Studies on the sardine oil. II. The change of color of sardine oil in relation to the absorbants. (In Japanese with English summary.) Bull. Japan. Soc. Set. Fisheries 7, 27-29.

Powick, W. C. (1925) . Inactivation of vitamin A by rancid fat. / . Agr. Research 31, 1017-1026.

Simons, E. J . , Buxton, L. O., and Colman, Η. B. (1940) . Vitamin A destruction in fish liver oils. Ind. Eng. Chem. 32, 706-708.

Smith, E. L. (1939) . Studies in the stability on vitamin A and D. II. Action on fatty peroxides on vitamin A. Biochem. J. 33, 201-206.

Swern, D., Scanlan, J . T., and Knight, Η. B. (1948) . Mechanism of the reactions of oxygen with fatty materials. Advances from 1941 through 1946. / . Am. Oil Chemists Soc. 25, 193-200.

Toyama, Y. (1952) . The oxidation of unsaturated fatty acids. Mem. Fac. Eng. Nagoya Univ. 4, 121-146.

Toyama, Y., and Matsumoto, I. (1953) . Volatile substances formed by air oxidation of the methyl ester of highly unsaturated acids. (In Japanese.) / . Chem. Soc. Japan Ind. Chem. Sect. 56, 972-973.

Venolia, A. W., Tappel, A. L., and Stansby, Μ. E. (1957) . Oxidative deterioration in fish and fishery products. III. Progress on investigations concerning reactions resulting in brown discoloration. Com. Fisheries Rev. 19 (5a) , 32-34.

Whipple, V. D. (1936) . The destruction of vitamin A by rancid cod liver oil. Oil <b Soap 13, 231-232.

Rancidity Problems in Fish Banks, A. (1937) . Rancidity in fats. I. The effect of low temperatures, sodium

chloride, and fish muscle on the oxidation of herring oil. J. Soc. Chem. Ind. (London) 56, 13-15T.

Banks, A. (1938a). The storage of fish with special reference to the onset of rancidity. I. The cold-storage of herring. / . Soc. Chem. Ind. (London) 57, 124-128T.

Banks, A. (1938b). Rancidity in fats. Dept. Sei. Ind. Research (Brit. Govt.) Rept. Food Invest. Board 1937, 73-74; (1939) . Chem. Abstr. 33, 252.

Banks, A. (1939) . Rancidity in fats. Dept. Sei. Ind. Research (Brit. Govt.) Rept. Food Invest. Board 1938, 106-112; (1940) . Chem. Abstr. 34, 2942.

Banks, A. (1944) . A method for studying the effect of antioxidants on the oxidation of aqueous suspensions of unsaturated fatty acids. / . Soc. Chem. Ind. (London) 63, 8-13.

Banks, A. (1952) . The development of rancidity in cold-stored herrings: The influence of some antioxidants. / . Set. Food Agr. 3, 250-256.

Banks, A. (1955) . Recent developments in the freezing of fish at sea. Chem. ir Ind. (London) 1955(43), 1360-1362.

Brown, W. D., Venolia, A. W., Tappel, A. L., Olcott, H. S., and Stansby, Μ. E. (1957) . Oxidative deterioration in fish and fishery products. II. Progress on studies concerning mechanism of oxidation of oil in fish tissue. Com. Fisheries Rev. 19(5a) , 27-31.


Charnley, P. (1945) . The measurement of spoilage in herring stored under moderately low temperature conditions. Analyst 70, 168-172.

Dyer, W. J . (1951) . Protein denaturation in frozen and stored fish. Food Research 16, 522-527.

Einset, E. , Olcott, H. S., and Stansby, Μ. E. (1957) . Oxidative deterioration in fish and fishery products. IV. Progress on studies concerning oxidation of extracted oils. Com. Fisheries Rev. 19 (5a) , 35-37.

Hashimoto, T., Shiina, H., and Tsuchiya, T. (1946) . Characteristics of the oils extracted from fresh and stale sardines. Unpublished.

Hills, G. L., and Conochie, J . (1945) . The oxidant effect of commercial salt in fats and oils. / . Council Sei. Ind. Research 18, 355-365; (1946) . Chem. Abstr. 40, 3623.

Khan, M. M. R. (1952) . A study of the "lipoxidase" in the flesh of British Columbia herring. / . Fisheries Research Board Can. 9, 393-416.

Lassen, S., Bacon, Ε. K., and Dunn, H. J. (1951) . Fish reduction process. Relation of yields and quality of products to freshness of raw material. Ind. Eng. Chem. 43, 2082-2087.

Tarr, H. L. A. (1944) . Antioxidants and prevention of rancidity in certain Pacific Coast fish. Nature 154, 824-826.

Tarr, H. L. A. (1948) . Control of rancidity in fish flesh. II. Physical and chemical methods. J. Fisheries Research Board Can. 7, 237-247; (1949) . Chem. Abstr. 43, 1498.

Venolia, A. W., Tappel, A. L., and Stansby, Μ. E. (1957) . Oxidative deterioration in fish and fishery products. III. Progress on investigations concerning reactions resulting in brown discoloration. Com. Fisheries Rev. 19(5a) , 32-34.

Biochemistry of Fish Oils

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