QUALITY OF WHOLE GUTTED SALMON IN VARIOUS BULK PACKAGES

QUALITY OF WHOLE GUTTED SALMON IN VARIOUS BULK PACKAGES

MORTEN SIVERTSVIK'.', JAN THOMAS ROSNES', AASE VORRE', KATI RANDELL', RAIJA AHVENAINEN'

and HELGE BERGSLIEN'

'NORCONSER V. P.O. Box 327, N-4001 Stavanger, Norway Vi'T Biotechnology and Food Research

P.O. Box I500 FIN-02044 V n . Finland

Accepted for Publication June 1 , 1998

ABSTRACT

Quality attributes of whole, gutted salmon (Salmo salar) were observed during chilled storage and transportation (<IC) in various bulk packages. The bulk packages used were plastic pouches with whole salmon and modified atmospheres (MA) (50% and 100% CO 3, large tubs with whole salmon in MA (60% C 0 2 and air), and traditional EPS-packages with whole salmon. In all bulk packages, except traditional packages, half or less the normal amount of ice were used. The microbial growth was evidently higher in traditionally packed salmon compared with salmon stored in atmosphere with high C0,-content. High C0,-content in the package inhibits bacterial growth more than low C0,-content. Salmon in MA were evaluated as equal or better sensoly quality than traditionally packaged salmon afier 13 days ofstorage. MA had, however undesirable effects on the appearance of whole salmon: faster graying of gills and loss of clearness in eyes.

INTRODUCTION

Farmed Atlantic salmon (ca 22 kg) is usually packed with ice (ca 7 kg) in standard EPS-packages (expanded polystyrene). Normal transport time from the slaughterhouse to the retailer is about 2-3 days, but may in some cases last up to one week depending on the market. There are few publications on how different bulk packaging methods influence the quality of the fish during transport and storage and how the type of bulk packaging influences the quality of the retail

'To whom to address correspondence.

Journal of Food Quality 22 (1999) 387-401. All Rights Resewed. 'Copyright 1999 by Food Ck Nutrition Press, Inc., TNmbulI, Connecticut. 387

388 M. SIVERTSVIK er al.

fillets subsequently packaged. Although there are numerous articles about modified atmosphere packaging of fish (Davies 1995; Reddy et al. 1992; Skura 1991; Stammen et al. 1990), bulk storage experiments of whole salmon in modified atmosphere has not been described in the literature. Bulk storage of salmon fillets (Oncorhynchus kisutch and 0. keta) in air-tight bulk containers has been reported to have an acceptable sensory shelf-life of 21 days in 90% CO, atmosphere at OC (Barnett et al. 1982). In bulk storage of whole cod (Gadus rnorhua) in CO, a shelf-life increase of at least 4 days was observed compared with air stored cod (Einarsson and Valdimarsson 1991).

Few studies have been published about the combination of bulk and retail packaging of fresh fish. The studies described here were carried out to examine the quality changes of salmon during storage and transport using different bulk and subsequent retail packaging techniques. The results can be applied when planning export of fish or when planning retail packaging of fish. The retail part of the study is reported separately (Randell et al. 1999). The bulk part is published in this article.

MATERIALS AND METHODS

Packaging, Transport and Storage

The research was carried out in two combined transport and storage studies. In study I, farmed Atlantic salmon (Salrno salar, size 3-4 kg, Ryfisk, Hjelmeland, Norway) were slaughtered, gutted and packed in traditional EPS (expanded polystyrene) packages, ca 22 kg salmon, 7 kg ice) and transported to NORCON- SERV the same day. The packages were stored unopened in chilled condition (3C) until repackaging the following two days. Bulk packaging types were as follows:

Single MA-pouches. One whole salmon in each pouch (CVP-Norge, Oslo, Norway). The package was vacuumized, filled with gas-mixture and sealed on a snorkel type packaging machine (CVP 4-300, CVP-Norge). Initial gas mixture in pouches were 49.4:49.8:0.8% (CO,:N,:O,). Four pouches were always packed in one nonisolated cardboard transport case (Petterson Ranheim, Trondheim, Norway, size 800x400~110 mm) with 2 kg of ice outside of the plastic pouches. Gadproduct volume ratio was ca 0.25.

Large MA-pouches. Five to six salmon were packaged in large double layer plastic pouches (Walkivent, United Paper Mill, Walki Pack, Valkeakoski, Finland) together with dry-ice (34 g solid COJ (HydroGas, Oslo, Norway). The pouch was

QUALITY OF WHOLE GUTTED SALMON 389

vacuumized and sealed on the snorkel type packaging machine. The pouch were placed in nonisolated transport case (high density polyethylene (HDPE), Dynoplast, Stjordal, Norway, size 800x400x200 mm) with 3 kg of ice placed outside of the plastic pouch as cooling agent. The gas mixture in the pouch after sublimation of dry ice was close to 100% CO, and the gaslproduct volume ratio was approxi- mately 0.25.

Traditional EPSpackage. Salmon was packaged in traditional isolated transport case made of expanded polystyrene, with normal amount of ice (approx. 7 kg). The fEh were packaged at the slaughterhouse (Ryfisk, Hjelmeland, Norway).

Samples of all bulk types were transported in chilled conditions to a retail store (Super-Vexi, Helsmki, Finland) by a tandem trailer (Sties, Stavanger, Norway). The temperatures in the bulk packages during transport were measured with electronic portable temperature loggers (Hamster, Elprolog, Buchs, Switzerland). The transport time was 4 days, the salmon leaving Norway the second day after slaughtering. Bulk packages were stored at chilled conditions in Finland (+2C) and samples from day 7 and 13 after slaughtering were analyzed for microbiological, chemical and sensory quality. Whole salmon from each bulk package type were collected for filleting and retail packaging according to Randell et al. (1999) on the seventh day after slaughtering. Nontransported samples of all bulk-packaging types were also stored in Norway at chilled conditions (3C f 1C) and analyzed on day 7, 13 and 16 after slaughtering.

In study II, farmed, whole gutted, Atlantic salmon (Salmo salar, size 4-5 kg, Northern Seafood, B0 i VesterHlen, Norway) were slaughtered and packed into three different bulk packaging types: 305 kg fish and 30-50 kg ice in a noninsulated plastic tub with air in tub headspace (Air tub). 314 kg fish and 30-50 kg ice in a noninsulated .and airtight plastic tub (Gas tub). The gas tub was filled with a gas mixture of CO, and N, (60%-40%)(Hydrogas, Oslo, Norway) flowing through valves in the tub until headspace gas composition was equal to the gas mixture. The valves were then closed. Both tub types were filled with snowhce in turn with salmon, beginning and ending with snowlice. Gaslproduct ratio in tubs was about 1 .O. The quality of tub-packaged salmon was compared with salmon packaged in traditional EPS packages. After packaging, the different packages were transported to Finland by tandem trailer under chilled conditions. The temperature in top and bottom of the bulk packages during transport were measured with electronic portable temperature loggers (Hamster, Elprolog, Buchs, Switzerland). The salmon were removed from the bulk packages upon arriving in Finland (two days after slaughtering) and samples from top and bottom of the two types of tubs and from the traditional package were analyzed for microbiological, chemical and sensory quality, before retail packaging (Randell et al. 1999).


Gas Analysis

The head-space gas composition (0, and CO, concentration) in the gas packages was determined by injecting an aliquot (30mL) of the head-space gas of the bulk package using an oxygen and carbon dioxide analyzer (in Norway: MAPtest 2000, Hitech Instruments, Luton, UK, in Finland: Combi Check 9800-1 analyzer, PBI-Dansensor, Ringsted, Denmark).

Microbial Analysis

Sampling for microbiological analysis of whole salmon was carried out from a standardized cut between the back fin and the gut opening of the whole salmon. Samples were taken aseptically as follows: the outside of the package was cleaned with ethanol. All instruments were also flamed with ethanol. The package was opened with a knife. Several pieces of fish meat were cut in Petri dishes with a pair of scissors. Ten grams of sample was put into a sterile Stomacher-pouch with tweezers. Room-tempered autoclaved peptone-saline-solution, 90 mL, (Maximal Recovery Diluent, Lab M, Bury, England) was poured into the pouch. The contents of the pouch were homogenized with a Stomacher-machine for 30 s. Further serial dilutions were made in sterile tubes containing autoclaved peptone-saline-solution before plating. The media and incubation parameters used were: Aerobic mesophilic bacteria Iron Agar (Oxoid, Basingstoke, Hampshire, UK), 30C, 3 days in Norway and Plate Count Agar (Difco, Detroit, MI), 30C, 3 days in Finland; psychrophilic bacteria Plate Count Agar (Difco), 7C, 10 days; coliforms Violet Red Bile Agar (Difco), 37C, 2 days; and H,S producing bacteria Iron Agar (Oxoid, ibid.), 30C, 3 days in Norway and Peptone Iron Agar (Difco) + L-Cysteinum chloride 0.04% (w/v) (Merck, Germany), 25C, 3 days in Finland. Microbiological analysis were carried out in triplicate (in Norway) or in four replicates (in Finland).

Sensory Evaluation

The raw salmon was evaluated both as whole fish, cutlets and fillets. In both studies the eyes, skin, gill appearance and gill odor of whole salmon was evaluated with a quality scale from 4 to 10 (4 = unfit, major defects, 10 = excellent, no defect) of a panel consisting of 4 (in Norway) or 2-3 (in Finland) trained assessors with proven skills. For samples tested in Finland the color of the gills of raw salmon were also measured using Minolta Chroma Meter 11 Reflectance (Minolta, Osaka, Japan). The sample L*a*b* chroma was determined and the a*co-ordinate (redness) was reported. In study I1 the odor of raw fillets were evaluated using the same panel as above and a quality scale from 1 to 9 (1 = unfit (fecal, indole and

QUALlTY OF WHOLE GUTTED SALMON 39 1

skatole), 9 = excellent (sea fresh, typical of species)). The color of raw fish meat was evaluated on both studies with a color atlas for salmonoids (Hoffmann-- LaRoche, Basel, Switzerland). In Norway evaluation was carried out on salmon-- cutlets (with a scale from 1 (light, yellow) to 8 (dark, red)) inside a light box (Nortech Ide AS, Bergen, Norway) with standard light source (Phillips TLD 18w/950) and neutral background. In Finland the salmon-fillets were evaluated with a scale from 11 (light, yellow) to 18 (dark, red) under lights with the same spectrum as day light (L 18W- 1 XC, Airam, Finland).

In study I sensory evaluation of cooked salmon were carried out using different scoring schemes in Norway and Finland. In Norway salmon samples (cutlets 15-20 mm wide) from the different packaging types were packaged in cook-plastic pouches (PA/PE 20/50) under slight vacuum and cooked in water vapor without any salt or spice addition. Using a scale from 1 to 7 the color intensity and shade (1 = white/yellow, 7 = strong, red), odor and flavor intensity (1 = neutral, 7 = strong), off- and rancid odor and flavor (1 = none, 7 = strong, rancid), firmness and juiciness (1 = soft, dry, 7 = fm, juicy) of the salmon samples were evaluated. In Finland salmon fillets were cooked similarly but in aluminum foil pouches and evaluated using a scale from 0 to 5 (0 = unfit, major defects, 5 = excellent, no defects) on parameters, appearance, odor, taste, texture and total quality of the samples. Both analysis were carried out using panel of 10 assessors, all selected and trained according to ISO-standard (1993). All sensory evaluations were carried out in randomized order of coded samples with replicate. In study I1 the sensory evaluation of cooked samples was carried out as described in study I on salmon fillets in Finland, and evaluated there with the same scale as in Norway in study I.

Statistical Analysis

Analysis of variance was carried out to veri., differences between the samples fiom every sensory evaluation except on raw fillets and cutlets where only 2 - 4 assessors evaluated the fillets. Fisher's least significant difference (LSD) procedure was used to determine significant differences between means.

TBA Analysis

The development of 2-thiobarbituric acid reactive substances (TBARS) in samples in study I were determined spectrophotometrically in duplicate according to Vyncke (1970) modified as described by Bjerkeng and Johnsen (1995).


K-Value Analysis

K value was used as an indicator of freshness of raw fish and it is determined from the breakdown products of adenosine nucleotides. K values of samples in study I were determined using colometric rapid method (Fresh Tester FTP 11, Ref FT 0302; Transia; Lyon, France) in duplicate. In addition K-values were analyzed with HPLC according to Ryder’s method (1985) in triplicate for samples analyzed in Finland.

Formation of Drip

The drip formed in the samples in study I during storage was measured gravimetrically. The mass of the drip (g) was divided by the initial mass of product (g) and reported as a percentage (%).

RESULTS AND DISCUSSION

Gas Composition

In study I in both studies, the gas composition in traditional EPS packages was equal to the normal gas composition of air during the whole experiment (20.9% O,, 0.03% CO,). For the other packaging types in study I the C0,-concentrations dropped the first week of storage because of absorption of CO, into the fish. After 7 days the C0,-level had stabilized at about 50% of initial level in both type 1 and 3 packaging. There were only minor differences between gas compositions in packages of the same type transported to Finland and packages stored in Norway.

In study I1 the initial gas composition in the gas tub was 60% CO, and 40% N,. The gas composition was not analyzed upon arrival in Finland, but negative pressure inside the gastub indicated absorption of the C02 and an airtight tub. The air tub headspace was equal to air, but microbiological results reported below indicated anaerobic conditions existed in the bottom of the air-tub.

Temperature During Storage

In both studies the temperature of the fish in all bulk packages never exceeded lC, which is below the lowest temperature (3.3 C) Clostidium botulinum type E has


been proven to grow and produce toxin (Skura 1991). A good temperature control (<3C) during the whole transportation and storage time is of greatest concern to ensure microbial safety and long shelf-life.

The temperature inside the bulk-package types in study I during transport was low (0-OX). During the subsequent 6 days storage in Finland the temperature inside the packages was below 1C. The temperature was slightly lower in the traditional EPS-packages probably due to more ice inside the packages.

The temperatures in tubs in study 11 were very stable throughout transportation. In the air-tub the temperatures varied between 0 and O X and in the gas-tub between -0.2 and 0.3C. In both tubs the highest temperatures were measured in the bottom of tub. The slightly lower temperature in the gas-tub is probably due to the different construction and better insulation in this type of tub.

Microbiological Quality

In the study I the salmon packed in modified atmospheres (MA) was of a better microbial quality than salmon packed in traditional EPS-packages. Almost no growth of mesophilic (Fig. l), psychrophilic (Fig. 2) and H2S-producing bacteria (not shown) were observed during the first 7 days of bulk storage, except in salmon packed in EPS and stored in Norway, in which microbial counts were 10-100 times higher than in salmon in other package types. The slowest growth of mesophilic, psychrophilic and H,S-producing bacteria were observed in the large MA-pouches, corresponding with the highest carbon-dioxide level (initially 100%). Transported salmon from the same packaging types had better microbial quality than nontransported salmon, due to an average 2 degree lower temperature during transport and storage. Growth of col i fom was observed in the salmon repackaged into MA-packaging types at the end of the storage. In the traditional packaged salmon, which had not been repackaged no coliforms were observed.

In study I1 only small differences of microbiological quality (Fig. 3) were detected between the salmon in the two tub types and in the EPS-packages after two days transport. The microbiological quality of salmon at the top of the gas tub was slightly better than in the bottom of the gas tub whereas the quality of salmon at the top of the air tub was worse than in the bottom of the tub. The quality in the bottom of the gas tub was worse than in the bottom of the air tub. This might be due to the few centimeters layer of liquid (melted ice and drip) in the bottom of the gas tub. In the bottom of the air tub, all the liquid had become ice. Fishes in the traditional EPS-packages had the lowest mesophilic counts and average psychrophilic counts when compared with fishes in tubs. No coliforms or H2S producing bacteria were found in whole fishes upon amval Finland.

394 M. SIVERTSVIU tz al.

8 , I 1 - -

1 - -

+-Single MA-pouch +Traditional pack -+Large MA-pouch +Single MA-pouch: Transported +Traditional pack Transported +Large MA-pouch: Transported

0 4 4 0 5 10 15 20

storage time after slaughtering (d)

FIG. 1. EFFECT OF THE PACKAGE AND STORAGE TIME ON MESOPHILIC PLATE COUNT IN WHOLE SALMON IN STUDY I

The data represent the means of two duplicate samples. The numbers indicate the bulk package type. Transported indicating whole salmon transported to Finland.

1 - -

1 --

+Single MA-pouch +Traditional pack +Large MA-pouch +Single MA-pouch: Transported -Traditional pack Transported +Large MA-pouch Transported

0 4 4 0 5 10 15 20

storage time after slaughtering (d)

FIG. 2. EFFECT OF THE PACKAGE AND STORAGE TIME ON PSYCHROPHILIC PLATE COUNT IN WHOLE SALMON M STUDY I

The data represent the means of two duplicate samples. The numbers indicate the bulk package type. Transported indicating whole salmon transported to Finland.


Mesophilic Psychrophilic

W Air tub -top W Air tub -bot W Gas tub -to11 W Gas tub -bot W Traditional pack

FIG. 3. EFFECT OF THE PACKAGE TYPE ON MESOPHILIC AND PSYCHROPHILIC PLATE COUNT IN WHOLE SALMON AFTER TWO DAYS TRANSPORT IN STUDY 11

The data represent the means of two duplicate samples.

Sensory Quality

In study I, color measurements of the raw salmon meat by color atlas showed that the meat became lighter at the end of the storage period. Salmon from the large MA-pouches was evaluated as the lightest at day 16 after slaughtering. The eyes of salmon rapidly lost their clearness and brightness during storage (Table 1). The loss was greatest in the MA-packaging types, and after 7 days the eyes were evaluated as slightly sunken and gray. The eyes of traditionally packed salmon were evaluated as better, clear, but flat and slightly gray. After 13 and 16 days the salmon in large MA-pouches (with the highest C 0 2 level) got the lowest scores, followed by single MA-pouches and traditional packages having the highest scores. Evaluation of the slun of whole salmon showed the same loss of quality as the evaluation of eyes. The skin of traditionally packed salmon was evaluated as of better exterior quality than that from the other bulk packaging types throughout the storage time. Appearance of the s h of fuh in packages transported to F d a n d was evaluated as slightly better than the skin of fuh stored in Norway after 13 days after slaughtering. The gills also rapidly lost their fresh odor and appearance, fastest in the large MA-packages with the highest C0,-level. However, after 13 and 16 days the differences between the packaging types were small, traditional packaged salmon having slightly better scores. This was confirmed by the Minolta-mea- surement performed on fish transported to Finland where small differences in the color of raw salmon meat were observed in the samples (data not shown).

3% M. SIVERTSVM et al.

Traditional pack. LargeMA-pouch T: Single MA-pouch T Traditional pack. T. Large MA-pouch

Packageb Single MA-pouch Tradtionalpack. LargeMA-pouch T. Single MA-pouch T: Traditional pack. T . Large MA-pouch

TABLE 1 . EFFECT OF PACKAGING. TRANSPORTATION AND STORAGE TIME ON EXTERIOR

QUALITY' OF WHOLE RAW SALMON IN STUDY I.

9 3 f 0.6 8.5 f 0.8 7 0 f 0 6 7.2 f 0.8 10.0 f 0 0 8.8 * 0.8 7.7 * 0.5 7.5 f 0 8 9 . 3 f 0 . 6 7 . 2 f 0 . 8 5 . 8 * 1 5 5 . 5 ~ l . 2 1 0 . 0 f 0 . 0 8 . 5 ~ 0 . 8 7 0 ~ l . I 6 . 2 * 1 . 3

7.2 i 0.4 5 . 5 f 0.6 8.0 f 0 0 7.0 f 0.0 6.9 f 0.3 5 0 f 0.0 Appearance of gills

Od 7 d 13d 16d Od 7 d 13d 16d 10 0 f 0.0 8.7 f I .4 5 2 f I .O 4.8 f 0.4 10.0 f 0.0 8.7 f 1.4 5.3 f I . 2 5 2 f 0.8 1 0 . 0 * 0 . 0 8 . 3 * 2 . 0 6 . 5 k 0 . 5 5 . 8 f 1 . 0 1 0 . 0 * 0 . 0 8 . 2 f 1 1 . 7 7 . 0 * 0 . 9 6 . 2 f 0 . 8 10 .0+0 .06 .2*11 .0 5 . 7 f 0 . 8 5 . 2 f 0 . 8 1 0 . 0 * 0 . 0 6 . 3 f 1 . 2 5 . 8 ~ 1 . 6 5 . 7 f 0 . 5

9.0 f 0.0 8.0 f 0 0 8.9 f 0.8 8.3 f 0.5 8.3 * 0.5 8.0 f 0 0

Odor of sills

7.7 f 1.0 7.2 f 0.8 8.1 1.0 5.3 t 0 . 8 7.1 f 1.5 4.5 0 6

8.2 f 0.4 5.3 * 0.5 9.0 f 1.0 5.2 f 0.8 7.6 * 1.2 5.3 f 0.6

I Eves I SkUl Packageb I Od 7 d 13d 16d I Od 7 d 13d 16d Smqle MA-pouch 19 3 f 0 6 7 8 f I 0 5 8 f I 6 5 7 f 10110 O * O O 9 2 f0 8 6 2 f I 8 5 8 f 0 4

The results from the sensory evaluations of cooked salmon stored in Norway showed little differences between the packaging types (Table 2). At the end of storage (1 6 days), a slight off-odor and off-flavor was observed in salmon from all other packages except from large MA-pouches. Strongest off-odor and off-flavor was noticed in salmon stored in single MA-pouches. Off-odor and off-flavor from salmon stored in EPS and large MA-pouches were very weak. The same tendency was observed in the results from sensory evaluation of odor intensity, flavor intensity, rancid odor and rancid flavor. The salmon in the single MA-package had a higher flavor and odor intensity and a slight rancid odor and flavor (Table 2). As for evaluation of salmon juiciness and firmness, the fish from single MA-package was evaluated as f m e r and dryer than the salmon from other packaging types. Salmon transported to Finland in single and large MA-pouches had slightly better sensory quality than salmon in traditional package.

In study 11, the whole fishes were only two days in bulk package thus their sensory quality was quite similar in all bulk package types. The only differences were noticed in the eyes and skin; they were brightest in salmon in the top of air tub and in the traditional packages (Table 4). According to Minolta-measurements,


fishes from traditional packages and from top of air tub had the reddest color of gills while fishes from bottom of air tub and top of gas tub had the most brown/- gray color of gills (data not shown). There were probably anaerobic conditions in the bottom of the air tub and the top of the gas tub, which caused the discoloration of gills. The sensory evaluation of cooked salmon after transport in study I1 showed increased off-odor and flavor and increased rancid odor and flavor at the top of both the gas and air tub, compared with salmon in the bottom of tubs and in traditional packages (Table 5) . The flavor and odor intensity was similar for the salmon packaged in the top and bottom of both tub types. The flavor intensity in the traditional packaged salmon was lower (but not significantly) than the salmon in tubs.

TABLE 2 EFFECT OF PACKAGING AND STORAGE TIME ON SENSORY QUALITY' OF

COOKED SALMON FLLETS STORED IN NORWAY IN STUDY I

' Mean scores of two samples and 10 assessors evaluated with a scale from 1 to 7 (Odor and flavor intensity (1 = neutral, 7 = strong), off-odor and flavor (1 = none, 7 = strong). rancid odor and flavor ( I = none, 7 = strong, rancid))

The same letter in each column after the mean indicates no significant difference between the samples (p<O.OS)

Bulk packaging type, stored in Norway at chilled conditions.

TBARS Values

TBARS-values of all samples remained low (< 0.75 m a g ) during the storage time indcating that the samples did not become oxidized before the end of storage.

398

Transportedpackageb T: SingleMA-pouch T: Traditional pack. T:LargeMA-pouch

M. SIVERTSVM et al.

Appearance Odor Texture Flavor Total Qualitr 7 d 13 d 7 d 13d 7 d I3 d 7 d 13d 7 d I3 d

3.6a 3.7a 3.7a 3.2a 3.9a 3.5 a 3.7a 3.1 a 3.6 a 3 .0a 3.6a 3 .6a 3.7a 3.1 a 3.8 a 3.2a 3.7a 2.8a 3 .7a 2.8a 3.7a 3.6a 3.9a 3.0a 3 .8a 3 .4a 3.8a 3 . l a 3 .7a 3 . l a

TABLE 3 EFFECT OF PACKAGING AND STORAGE TIME ON SENSORY QUALITY' OF

COOKED SALMON FILLETS TRANSPORTED TO FINLAND IN STUDY I.

Air tub -bot Gastub-top Gas tub -bot Traditionalpack.

7.8*1.0 9 .04~0 .6 8.5*1.1 9 . 2 t 0 . 8 8.5*0 .8 16 .0 t0 .0 7.5*0.6 8.0*0.0 8.5*0.6 9.3*0.5 8.2*0.8 16.0*0.0 8.2*0.4 8 .8*0 .8 8.7*0.5 9.0*0.9 8.7*0.5 15.5*0.6 9.0*0.0 9.5*0.6 8 . 2 i 1 . 0 8.8*1.0 8.7*0.5 16.0*00

TABLE 4. EFFECT OF PACKAGING ON EXTERIOR QUALITY' OF WHOLE SALMON, AND

ODOR^ AND COLOR^ OF RAW SALMON FILLETS IN STUDY II

Packaged I Eves Skin Colorof Odorof Odorof Colorof - gills gills fillets fillets

Air tub -top 19 .1*0 .4 10.OiO.O 8.8*1.0 9.5*0.8 8 . 3 i 0 . 8 15.5*0.6


TABLE 5 . EFFECT OF PACKAGING ON SENSORY QUALITY' OF COOKED SALMON FILLETS

IN FMLAMl (STUDY II).

Packa e Off-odor' Off-flavor. Rancid odof Rancid flavor' Air tub -top 2.0 ab Air tub -bot 1.7 ab G a s tub -top 2.2 b Gas tub -bot 1.5 a 1.7 a 1.2 a 1.5 ab Traditional ack. 2.0 ab 1.4 a 1.3 ab 1.3 a

flavor intensity ( 1 = neutral, 7 = strong), off-odor and flavor ( 1 = none, 7 = strong), rancid odor and flavor (1 = none, 7 = strong, rancid))

Bulk packaging type, two day transport from Noway to Finland, top = salmon from top of tub. bot = salmon 6om bottom of tub. The same letter in each column after the mean indicates no significant difference between the samples (p<O 05)

Mean scores of two samples and 10 assessors evaluated with a scale from 1 to 7 (Odor and

K-Values

The results from the paper strip method were much lower than results from the HPLC method (data not shown). This was also observed in the retail part of the study (Randell et al. 1999). The K-values developed fastest in the traditional packaged salmon stored in Norway (paper strip test) and Finland (HPLC-test). No differences were observed between the K-value of the samples in different package types in Finland, and the values for salmon in single and large MA-pouches were similar as those observed in Norway.

Formation of Drip

The formation of drip in all the packages was very small. Seven days after slaughtering there was almost no measurable drip. After day 13, the drip formation in the salmon in single and large MA-pouches was still very low (approx. 0.3%). Drip formation from the salmon in the traditional EPS packaging and in the tubs was impossible to determine since the ice was allowed to drain out of the packages.

CONCLUSIONS

MA could be used for bulk transportation of salmon. The salmon packaged in MA kept a better microbiological quality, based on mesophilic, psychrophilic

400 M. SIVERTSVIK ef al.

and H,S-producing bacteria counts, than salmon packaged in traditional packaging, even with the use of half amount of ice. In study I, when the salmon arrived in Finland, it’s microbial and sensory quality were good. Higher carbon dioxide content in the package inhibited bacterial growth more than lower or no carbon dioxide content in the atmosphere. The MA had an unfortunate effect on the appearance of raw whole salmon, because of faster graying of gills and loss of clearness in eyes. There were no big differences between the cooked sensory quality of the samples including day 13 after slaughtering; however, the salmon that had been packaged in MA were evaluated as slightly better. The salmon were still acceptable after 13 days in all packages. The quality of salmon transported to Finland and salmon stored under stable chilled conditions in Norway were comparable and the transportation did not affect the microbiological, chemical or sensory quality. The packaging type best preserving the microbiological and sensory quality of salmon in this study was large MA-pouches with solid CO, giving - 100% CO, atmosphere in pouch.

In study 11, when the salmon arrived in Finland, its microbiological and sensory quality was very good. Since the transport from Norway to Finland was fast (2 days), the type of bulk package did not influence the quality of salmon as much as in the first transport study where salmon was in bulk packages for a longer period. The tub packages did not significantly increase the shelf-life of salmon when compared with the traditional bulk package. However, with the tub bulk packages it was possible to decrease the amount of ice used. The location of the salmon in the tub has slight effect on the microbiological quality. The only differences in sensory quality of bulk packed salmon in study I1 were noticed in the eyes and skin; they were brightest in salmon from the top of air tub and in the traditional packages.

MA could be used to reduce or eliminate the use of ice in the chilled distribution of salmon without reduction in eating quality, with a possible increase in tonnage salmon per truck and reduction in environmental pollution from biologically active ice-water drained from the trucks. However, even with MA-packaging, means must be taken to avoid contamination of product during handling and packaging of the fish and the salmon must be in chilled state (<3C) during all operations and during subsequent transportation and storage.

ACKNOWLEDGMENTS

This work was a part of a NordFood project “Fish, Packaging and Transport” and was kindly supported by the Nordic Industrial Fund, the Norwegian Research Foundation and participating industrial partners. The technical staff at NORCON- SERV and VTT is gratefully acknowledged for their skillful assistance.


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QUALITY OF WHOLE GUTTED SALMON IN VARIOUS BULK PACKAGES

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