PINK SALMON (ONCORHYNCHUS GORBUSCHA) QUALITY DURING ICE AND CHILLED SEAWATER STORAGE

PINK SALMON (ONCORHYNCHUS GORBUSCHA) QUALITY DURING ICE AND CHILLED SEAWATER STORAGE

BRIAN H. HIMELBLOOM',3, CHUCK CRAPO', EILEEN K. BROWN', JERRY BABBITT' and KERMIT REPPOND*

'Fishery Industrial Technology Center and 'National Marine Fisheries Service, Utilization Research Division

University of Alaska Fairbanks, 900 Trident Way Kodiak, AK 99615-7401

Accepted for Publication October 30, 1993

ABSTRACT

Pink salmon were stored up to ten days in ice, chilled seawater (CSW), transferred from ice to CSW and from CSW to ice, and evaluated by chemical, physical, microbiological, and sensory methods. The sensory quality of CSW-held fish declined at a faster rate than for iced fish. CSW-held fish had higher weight gain, higher salt and hypoxanthine levels and had softer texture than iced fish. Microbial counts were highest for iced fish and a two-log increase occurred during storage. Moraxelia species were predominanr in the microbial flora of iced fish whereas Pseudomonas species were predominant in the microbial flora of CSW-held fish. Ice was superior to CSW for maintaining salmon quality.

INTRODUCTION

Ice, chilled seawater (CSW; one part ice to two parts seawater) and refrigerated seawater (RSW) systems rapidly reduce the temperature, maintain quality and extend the shelf-life of fresh fish. A seawater system operated at - 1C is cited as an advantage over ice for storing fresh fish (Licciardello 1980). Peters et al. (1964) recommend holding whiting less than four days in ice or seven days in RSW. However, pink salmon held in RSW should be limited to three or four days (Tomlinson et al. 1974; Bronstein et al. 1985; Crapo and Elliot 1987). Benefits of RSW and CSW compared with ice are: a faster cooling rate, reduction in crushing of fish, economic savings in time and labor, and longer storage life of the fish (Stern and Dassow 1958). But RSW equipment is

'To whom correspondence should be sent.

Journal of Food Quality 17 (1994) 197-210. All Rights Reserved. Copyright 1994 by Food & Nutrition Press, Inc.. Trrtmbull, Connecticur 197

198 B.H. HIMELBLOOM, C. CRAPO, E.K. BROWN, J . BABBITT and K. REPPOND

easily contaminated and recirculation of blood, slime and bacteria may spoil the entire catch (Price 1983). It requires considerable maintenance and must sustain - 1C for effectiveness, although color leaching and salt absorption can occur (Price 1983). Small boat fisherman tend to prefer CSW because it is a simple mixture of ice and seawater unlike RSW which requires expensive, mechanical refrigeration (Licciardello 1980).

Low temperature is essential in reducing the growth rate of spoilage bacteria. A common problem with holding fish in seawater is the eventual growth of sufficient numbers of spoilage bacteria that taint the fish (Roach et al. 1961). Research on the effects of different chilling systems on seafood microorganisms is limited. Overall bacterial growth rate is reduced in dressed chinook salmon stored in chilled freshwater or seawater compared with ice storage (Bronstein et al. 1985). RSW is effective in controlling microbial spoilage of stored Pacific shrimp (Lee and Kolbe 1982). Microbial growth in and quality of pink salmon stored in RSW and halibut stored in CSW are temperature-dependent (Crapo and Elliot 1987; Crapo et al. 1991). Yet, no taxonomic studies have been done for determining the succession and predomi- nance of spoilage microorganisms in these storage systems.

The Alaska seafood industry uses CSW and RSW to hold salmon on tenders (small transport vessels) and fishing vessels. Fish are received at processing plants and typically are transferred into fresh CSW, RSW or ice. Industry has perceived an accelerated fish quality loss after transfer between chilling systems, i.e., RSW or CSW to ice or CSW (Jensen 1988). It is unknown which chilling system or combination most effectively maintains the quality of stored salmon. Our objectives were to measure the chemical, physical, microbiological and sensory changes of pink salmon stored in ice, CSW and transferred between the systems, and to determine the causes for accelerated quality loss.

MATERIALS AND METHODS

Fish

Pink salmon (Oncorhynchus gorbuschu) were harvested from the Gulf of Alaska around Kodiak Island, held in the round in ice and CSW totes and delivered within 12 h. Salmon (n = 120hreatment) were placed in fresh ice (OC) or CSW ( - O X ) and stored for ten days. CSW was prepared by mixing ice and water (1:2 wt:vol) with salt (final concentration of 3 % wt/wt). Fish were held in ice or CSW at a ratio of 3 parts fish to 1 part chilling medium to mimic industry practices. At three days of storage, a typical holding time aboard fishing vessels and tenders, fish were transferred to a fresh chilling medium. Fifty iced salmon were transferred to fresh CSW and fifty CSW-held salmon

PINK SALMON QUALITY 199

were transferred to fresh ice, the standard industry practice. Transferred fish were held for seven days. During storage, fish were removed from each system for evaluation.

Sampling and Analysis

Ten salmon in each system were tagged and used to monitor weight gained during ten days of storage. Weight gain was measured using an analytical balance (Model PE-11, Mettler Instrument Corp., Highstown, NJ). Each sampling day, ten salmon were picked randomly and graded according to specific criteria (Table 1). Two salmon from each chilling system were selected randomly and the skins swabbed for microbial enumeration and identification (Himelbloom et al. 1991a, b). Ice and CSW, used in storing the fish, were collected in sterile 250 ml polypropylene screw-capped jars (Nalgene, Sybron Corp., Rochester, NY) for microbial analysis.

TABLE 1 SALMON GRADING CRITERIA’

Grade Attribute

Excellent Good Fair Poor

Odor Fresh, seaweedy No odor, neutral Strong slime Odor Decomposing, acid odor

Eyes Bright, clear Flat, slightly opaque Opaque, slightly red Opaque, red, sunken

Skin Bright, no bleaching Slightly dull, wavy Dull, some bleaching Dull, bleached

Gills Bright red, no odor Pink. slight odor Green-brown, Brown-white, decomposed strong Slime odor

Flesh Firm Slightly soft Moderately soft Severely soft

Gut 8 roe Firm, bright, Soft no decomposition, Slightly liquid, darkening. Very liquid, dark, no decomposition slight discoioration slight decomposition noticeable decomposition

’ From Crapo and Elliot (1987)

Salmon were filleted and the flesh evaluated for salt, hypoxanthine, rancidity, texture and sensory analysis. Salt concentration was measured using AOAC (1984) method 24.01 1. Hypoxanthine levels were measured using the methods of Woyewoda ef al. (1986). Rancidity development was determined by the thiobarbituric acid (TBA) method (Lemon 1975).


Shear force was measured by an Instron Model 1000 (Instron Corp., Canton, MA) equipped with a Kramer-Lee shear cell using methods by Dassow et al. (1962). Three 5-cm sections beginning at the anterior portion of the fillets (n = 10) were cut into cubes (5 x 5 x 1 cm) and sheared across the muscle fiber using a 100 kg load cell with a load range of 10-50 kg. Crosshead speed was 300 mm/min with a 1 :2 proportional chart speed. Fillets (n = 10) were also frozen for 6 months at -18C then thawed prior to shear force testing.

Fish were evaluated after one month frozen storage by an experienced 12- member taste panel. Zero day fish served as controls. Samples were steamed in aluminum foil at lOOC for 6 min. Descriptive scales were used to evaluate flavor (1 = intense bad, 7 = excellent fresh), texture (1 = very tough, 7 = very tender) and moistness (1 = very dry, 7 = very moist). Statistical Analysis System (SAS 1985) procedures were used for analysis of variance and least significant differences between sample means.

RESULTS AND DISCUSSION

Chemical, Physical, and Sensory Changes

The initial quality of iced and CSW-held salmon was graded as excellent-to- good and having firm flesh, bright skin and fresh odor. The grading scores of CSW-held fish declined at a faster rate than for iced fish (Fig. 1). Salmon transferred from CSW to ice maintained slightly better quality than the CSW-held fish. Fish transferred from ice to CSW lost quality faster than iced salmon but slower than CSW-held fish. Bronstein et al. (1985) showed ice maintained better sensory attributes of chinook salmon during storage than RSW. Barnett et al. (1991) showed pink salmon retained excellent quality up to seven days in ice.

CSW-held salmon had a weight gain (p < 0.05) of 5% vs. 1% for iced fish. This agreed with studies showing pink salmon held in RSW gained 3.2-6.0% in weight while iced salmon gained 0.8% (Tomlinson el al. 1969; Crapo and Elliott 1987). Chinook salmon gained 5.45 % in weight in refrigerated fresh water and 4.0% in RSW, but lost 0.4% in ice after seven days of storage (Bronstein et al. 1985). Salmon transferred from ice to CSW gained weight, while fish transferred from CSW to ice lost the weight gained during the first three days of CSW storage (Fig. 2). The weight was gained from salt and water adsorption into the flesh.

Salt content in CSW-held salmon doubled (p < 0.05) from 0.23 % to 0.48% during ten days of storage while remaining constant at 0.11 % in iced salmon. This was expected since CSW contained 3% salt and ice was prepared from

PINK SALMON QUALITY 20 1

202 B.H. HIMELBLOOM, C . CRAPO, E.K. BROWN, J . BABBITT and K. REPPOND

6 * csw I

5 C .I

g4 5 .I 0 3

i, 8

1

0

0

1 3 5 7 9 Day

FIG. 2. PERCENT WEIGHT GAIN OF PINK SALMON HELD IN CSW AND ICE

0.8

0.6

+ I

v) 0.4 8

0.2

0

-t csw I I i I I

* Ice * CSW to tce

* Ice

/ , - n A

0

1 3 5 7 9 Day

FIG. 3. PERCENT SALT CONTENT IN PINK SALMON HELD IN CSW AND ICE


fresh water. In other studies, pink salmon stored in RSW had a salt content of 1.0% and 0.7% in CSW (Crapo and Elliot 1987; Tertnes et al. 1984). The salt content of sockeye salmon in RSW was 0.56% and 0.14% in ice (Tomlinson et al. 1974). Chinook salmon had a salt content of 1.0% after four days in RSW and 0.08% in ice (Bronstein et al. 1985). Iced fish transferred to CSW increased in salt content, but the levels were not different (p > 0.05). After transfer to ice, CSW-held fish lost salt but the change was not different (Fig. 3).

Hypoxanthine levels increased fastest in CSW-held salmon (Fig. 4). The increased rate of hypoxanthine accumulation may be attributed to increased water and salt uptake since the temperatures of both chilling systems were the same. Fish transferred from CSW to ice had a lower (p > 0.05) hypoxanthine accumulation as compared with CSW-held fish during the storage period from day 4 to day 8. During the same storage period, fish transferred from ice to CSW resulted in a higher (p > 0.05) accumulation of hypoxanthine than iced fish. By day 10, hypoxanthine concentrations for fish in the transferred systems were different (p <0.05) from those for iced fish and CSW-held fish. The initial hypoxanthine levels were slightly lower than those reported by Luong et al. (1992) and may have resulted from species difference or from better quality of pink salmon

800

600

E" 2 400 I P)

rt 200

0

* csw * Ice

-2 CSW to Ice

Ice to CSW

1 3 5 7 9 Day

FIG. 4. HYPOXANTHINE (HX) CONCENTRATION IN PINK SALMON HELD IN CSW AND ICE

204 B.H. HIMELBLOOM, C. CRAPO, E.K. BROWN, J. BABBITT and K. REPPOND

There were no differences (p > 0.05) in shear force of fillets over the ten days of chilled storage. CSW-held fish were softer (p > 0.05) than iced fish (Fig. 5 ) . This softening of CSW-held fish continued when placed in ice. After six months of frozen storage, fish that had been transferred between chilling systems had higher (p > 0.05) shear force than those held only in CSW or ice.

" csw Ice CSW to Ice Ice to CSW

S t o rag e Treat m en t

FIG. 5 . AVERAGE SHEAR FORCE FOR PINK SALMON FOLLOWING 10 DAYS OF STORAGE IN CSW AND ICE AND FROZEN FOR 6 MONTHS AT - 18C

Pink salmon retained acceptable fresh flavor when stored in ice or CSW for less than four days (Fig. 6). After four days in CSW, fish had declined (p < 0.05) in flavor scores and were considered spoiled at ten days. By contrast, the flavor of iced fish did not change (p > 0.05) in the first six days of storage. Fish transferred from ice to CSW lost flavor while those transferred from CSW to ice maintained acceptable flavor for four days of storage. After six days of storage, flavor loss (p < 0.05) occurred.

Rancidity development remained low in fish in the four treatments. After ten days of storage, no difference (p >0.05) in TBA values existed among the samples. The lowest TBA value (1.27 mg malonaldehyde/lOO g fish) occurred in iced fish while the highest (1.44 mg/100 g) was found in CSW-held fish.


I 3 5 7 9

Day FIG. 6. FLAVOR SCORES OF PINK SALMON HELD IN CSW AND ICE

Scores range from 7 = excellent flavor to 1 = poor flavor. Spoiled samples were assigned a value of zero.

These levels were much lower than those previously reported (Crapo and Elliot 1987) indicating high initial quality and low rancidity in the fish.

Microbiological Changes

The skin of iced salmon had the highest aerobic plate counts (APC) while CSW-held fish had a two-log lower APC throughout storage (Fig. 7). Bronstein et al. (1985) showed the microbial counts for dressed chinook salmon were lower in RSW-held fish than in iced fish. Salmon that had been stored on ice and transferred to fresh CSW resulted in a one-log APC decrease (Fig. 7). Adhering microbial flora of iced salmon may have sloughed off during mixing with fresh CSW. The low counts for CSW-held fish increased slightly after transfer into fresh ice. Microorganisms associated with harvested salmon had inoculated the ice and CSW initially and after fish transfer between chilling systems (Fig. 8).

206 B.H. HIMELBLOOM. C. CRAPO, E.K. BROWN, J. BABBITT and K. REPPOND

FIG. 7. AEROBIC PLATE COUNTS FOR PINK SALMON HELD IN CSW AND ICE

Moraxella was the predominant bacterial genus on whole salmon iced during eight days of storage (Table 2). CSW-held fish transferred to ice resulted in the resurgence of MoraxelEa at eight days of storage. Chai and Chen (1982) showed during storage of various fish species that Acinetobacter and Moraxella accounted for 60% of the microbial flora in melting ice. However, bacterial identifications of skin microbial flora from these fish were not attempted.

The genus Pseudomonas predominated the bacterial flora of salmon stored for eight days in CSW (Table 2). Iced fish transferred into CSW resulted in the decline, during the remaining storage time, of Moraxella and the resurgence of Pseudomonas. Lee and Kolbe (1982) showed for at-sea storage of Pacific shrimp that Pseudomonas species accounted for 71% of the microbial flora in RSW, while the microbial flora adhering to shrimp was predominated by Arfhrobacter species.


FIG. 8. AEROBIC PLATE COUNTS FOR CSW AND ICE

CONCLUSIONS

The loss in pink salmon quality was most rapid during storage in CSW. Compared with iced fish, the CSW-held salmon had higher weight gain, salt and hypoxanthine levels and softer texture. Hypoxanthine concentration, a relative quality measure for seafoods, was highest in CSW-held fish. The rate of hypoxanthine formation, combined with increased water and salt uptake in CSW, quickly lowered salmon quality, Sensory analysis confirmed the rapid decrease in quality. Bronstein et al. (1985) showed the sensory qualities of chinook salmon during RSW storage were lower when compared with iced fish.

Although the bacterial counts were higher for iced fish, an important quality index may be the microbial flora development during pink salmon storage. The role for Moraxeliu in iced seafoods has not been established but these bacteria are considered as low- to nonspoilage types. The skins of fresh sockeye salmon, Pacific halibut, Pacific cod, and Alaska pollock have microbial flora predominated by Moraxella (Himelbloom et al. 1991b, c).

CSW-held salmon had lower APC but the skin microbial flora was predominated by the genus Pseudomonas, which contains potent spoilage


TABLE 2. PERCENT DISTRIBUTION OF MICROBIAL FLORA ON PINK SALMON HELD IN CSW AND ICE'

Day Genus csw Ice csw to ICE Ice to CSW

1 Flavobacteriurn Moraxella Others

- - NCI: 47 54 APC: 4.8 x 102 76x104 - -

26 43 31

7 85

8

4 Acmetobacter Navobacterfum Moraxella Pseudomonas Others

NCI: APC'

8 Flavobacterium MoraxeNa Pseudomonas Others

NCI: APC.

25 40 15 20

0

23 2.3 x lo3

8 19 73 0

52 5.4 lo3

2 22 76

0 0

42 2.3 x lo4

36 23 8

26 7

9 5

59 1 1 16

42 4 6 x 1 0 ~

46 4 I lo3

32 66

0 2

47 2.7 x lo6

9 63 25 3

32 1.4 x lo4

6 29 65 0

34 3.1 lo4

'Data for the bacterial genera are shown as a percentage of the microorganisms enumerated. The designation "others" consists of a group of remaining identified genera (Acinetobacrer, Alcaligenes, Arthrobacter-Corynebacterium, Bacillus, Micrococcus, and yeast) of which no genera within the group amounted to greater than 10% of the microbial flora. NCI = number of colonies identified on plates containing the highest sample dilution. APC = aerobic plate

count/cm* of skin.

bacterial species of refrigerated protein foods (Liston 1982). Low percentages of Pseudomonas species were found in the skin microbial flora of fresh Alaska finfish (Himelbloom et al. 1991 b, c). The lower sensory values for CSW-held fish may have resulted from endogenous enzymatic reactions coupled with the growth and metabolism of Pseudomonas species on fish skin and in CSW.

After harvest, the loss in quality for CSW-held salmon occurred within four days, which is a typical fish tendering trip. These fish would be susceptible to spoilage and damage through handling. Salmon transferred from CSW vessels to ice would likely be more damaged than iced fish. Handling from fishing vessels to tenders to processing plants could easily accelerate quality loss. The transfer of CSW-held fish to ice may cause crushing of softened fish and the rapid loss in quality perceived by fish processors. We concur with previous studies and recommend storing harvested salmon for less than four days if CSW


systems are used. Ice was a better chilling system than CSW for maintaining the storage quality of pink salmon.

ACKNOWLEDGMENTS

We thank Mr. Ken Allread and Western Alaska Fisheries, Inc. in Kodiak for their cooperation and assistance in providing the salmon for this project. This work was supported by the Alaska Sea Grant College Program, under grant number NA90AA-D-SG066, project number A/7 1-01, and from funds appropriated by the state to the University of Alaska.

REFERENCES

AOAC. 1984. OflcialMethods ofAnalysis, 14th Ed., p. 432, Assoc. of Official Analytical Chemists, Arlington, VA.

BARNETT, H.J., NELSON, R. W. and POYSKY, F.T. 1991. A comparative study using multiple indices to measure changes in quality of pink and coho salmon during fresh and frozen storage. U.S. Dept. Comm., NOAA Tech. Memo, NMFS FfNWC-208, 51 p.

BRONSTEIN, M.N., PRICE, R.J., STRANGE, E.M., MELVIN, E.F., DEWEES, C.M. and WYATT, B.B. 1985. Storage of dressed chinook salmon (Oncorhynchus tshawytscha) in refrigerated seawater, diluted seawater, seawater, and in ice. Mar. Fish. Rev. 47, 68-72.

CHAI, H.C. and CHEN, T.J. 1982. Microflora of drainage from ice in fishing vessel fishholds. Appl. Environ. Microbiol. 43, 1360-1365.

CRAPO, C. and ELLIOT, E. 1987. Salmon quality: the effects of elevated refrigerated seawater chilling temperatures. Alaska Sea Grant Coll. Prog., Mar. Adv. Bull. 34, Univ. Alaska Fairbanks, 12 p.

CRAPO, C., LEE, J. and BROWN, E. 1991. Halibut quality: chilled seawater storage of dressed and round fish. Alaska Sea Grant Coll. Prog., Mar. Adv. Bull. 42, Univ. Alaska Fairbanks, 12 p.

DASSOW, J.A., McKEE, L.G. and NELSON, R.W. 1962. Development of an instrument for evaluating texture of fishery products. Food Technol. 18, 108-110.

HIMELBLOOM, B.H., BROWN, E.K. and LEE, J.S. 1991a. Microbiological evaluation of Alaska shore-based surimi production. J . Food Sci. 56,

HIMELBLOOM, B.H., BROWN, E.K. and LEE, J.S. 1991b. Microorganisms isolated from surimi processing operations. J . Food Sci. 56, 299-301.

HIMELBLOOM, B.H., BROWN, E.K. and LEE, J.S. 1991c. Microorganisms on commercially processed Alaskan finfish. J . Food Sci. 56, 1279-1281.

JENSEN, C. 1988. Private communication. Kodiak, Alaska.

291-293, 314.


LEE, J.S. and KOLBE, E. 1982. Microbiological profile of Pacific shrimp, Pandalus jordani, stowed under refrigerated seawater spray. Mar. Fish. Rev. 44, 12-17.

LEMON, D.W. 1975. An improved TBA test for rancidity. New Ser. Circ. No. 51, Environment Canada, Fish. Mar. Serv., Halifax, Nova Scotia, 4 p.

LICCIARDELLO, J.J. 1980. Handling whiting aboard fishing vessels. Mar. Fish. Rev. 42, 21-25.

LISTON, J. 1982. Recent advances in the chemistry of iced fish spoilage. In Chemistry and Biochemistry of Marine Food Products, (R.E. Martin, G.J. Flick, C.E. Hebard and D.R. Ward, eds.) p. 27, Van Nostrand Reinhold/ AVI, New York.

LUONG, J.H.T., MALE, K.B., MASSON, C. and NGUYEN, A.L. 1992. Hypoxanthine ratio determination in fish extract using capillary electropho- resis and immobilized enzymes. J. Food Sci. 57, 77-81.

PETERS, J.A., COHEN, E.H. and ALIBERTE, E.E. 1964. Improving the quality of whiting. U.S. Fish. Wild. Serv. Circ. 175, 16 p.

PRICE, R.J. 1983. Storage of dressed salmon in refrigerated sea water. Calif. Sea Grant Coll. Prog., Univ. Calif. Coop. Ext. Mar. Briefs No. 10, 2 p.

ROACH, S.W., HARRISON, J.S.M. and TARR, H.L.A. 1961. Storage and transport of fish in refrigerated sea water. Bull. Fish. Res. Board Can. 126, 61 p.

SAS. 1985. Statistical Analysis System Users Guide, SAS Institute, Cary, NC. STERN, J . and DASSOW, J.A. 1958. Technical note No. 43: Considerations

on the use of refrigerated brine for chilling and storing fresh fish. Comm. Fish. Rev. 20, 17-20.

TERTNES, G., LOSNEGARD, N. and LANGMYHR, E. 1984. Studies on the quality of fish held in chilled seawater and in ice. Part 6. Nonveg. Dir. Fish. Rep. Notes 6, Bergen, 10 p.

TOMLINSON, N., GEIGER, S . , BOYD, J. , SOUTHCOTT, B., GIBBARD, G. and ROACH, S. 1974. Comparison between refrigerated sea water (with and without added carbon dioxide) and ice as storage media for fish to be subsequently frozen. In Cooling and Freezing Aboard Fishing Vessels, pp. 163-168. Int. Inst. Refrig., Commissions B-2, D-3, Annex 1974-1, Paris.

TOMLINSON, N. , KRAMER, D., GEIGER, S. and ROACH, S. 1969. Weight changes in some species of Pacific Coast fish while stored in refrigerated sea water or in ice. Fish. Res. Bd. Canada, Vancouver Tech. Lab. Circ. 45, Vancouver, 12 p.

WOYEWODA, A., SHAW, S . , KE, P. and BURNS, B. 1986. Recommended laboratory methods for assessment of fish quality. Can. Tech. Rep. Fish. Aquat. Sci. 1448, 50-53. Dept. Fish. Oceans Canada, Ottawa.

PINK SALMON (ONCORHYNCHUS GORBUSCHA) QUALITY DURING ICE AND CHILLED SEAWATER STORAGE

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