Changes in the flesh of cooked farmed salmon (Oncorhynchus kisutch) with previous storage in slurry ice (−1.5 °C)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 Changes in the flesh of cooked farmed salmon (Oncorhynchus kisutch) with previous storage in slurry ice (-1.5ºC) Alicia Rodríguez a, Nicolás Carriles a, José M. Cruz b, and Santiago P. Aubourg c,* a Department of Food Science and Chemical Technology, Faculty of Chemical and Pharmaceutical Science, University of Chile, Santiago (Chile) b Department of Analytical Chemistry, Nutrition and Bromatology, University of Santiago de Compostela (Spain) c Department of Food Technology, Instituto de Investigaciones Marinas (CSIC), Vigo (Spain) * Correspondent: FAX: +34986292762; e-mail: [email protected] ABSTRACT1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Whole, farmed Coho salmon (Oncorhynchus kisutch) were sacrificed in slurry ice (-1.5ºC) then stored in this medium for further processing after 0, 5 and 9 days. They were cooked whole and the flesh was evaluated by sensory, physical and chemical techniques to establish if significant changes had occurred as a result of the storage period. Initial samples from harvest were also evaluated for comparison. There was evidence of increases in trimethylamine, lipid hydrolysis, lipid oxidation (anisidine and thiobarbituric acid values) and interaction compound formation (fluorescence and browning measurements). The fish structure became more breakable with longer storage but there were no changes in sensory assessments for rancid and putrid odours, so that scores were less than 0.5 on a 11 point scale. From the present results, primary and secondary lipid oxidation development and further interaction compound formation appears to be the main measurable indicators of quality changes in cooked Coho salmon. However, and according to sensory appreciation, slurry ice has shown to be a suitable medium for previous storage of Coho salmon for periods of up to 9 days. Key Words: Oncorhynchus kisutch, farming, chilling, cooking, deterioration, quality 19 Running Title: Quality deterioration in cooked farmed salmon 20 21 22 2 INTRODUCTION 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Cooking destroys pathogenic and spoilage microorganisms, inactivates enzymes and enhances desirable flavours and tastes of fish flesh (McLay, 1982). However, owing to the thermal sensitivity of a broad number of fish constituents and nutrients several detrimental effects due to cooking have been reported: i.e., heat degradation of nutrients, oxidation of vitamins and lipids, leaching of water-soluble vitamins, minerals and proteins, and toughening and drying of sensitive protein tissues (Aitken & Connell, 1979; Pigott & Tucker, 1990). Most of the quality problems found in cooked fish products are directly related to the initial quality of the fresh raw material, which declines continuously post-mortem during its preliminary refrigerated storage (Olafsdóttir et al., 1997). Accordingly, quality of processed fish will depend to a large extent on the adequacy of the preliminary holding methods used (Slabyj & True, 1978; Aubourg & Medina, 1997). In this sense, great efforts have been carried out in the search of appropriate chilling conditions so that autolytic degradation and microbial spoilage would be slowed and minimised (Whittle, Hardy, & Hobbs, 1990; Ashie, Smith, & Simpson, 1996). In recent years the fishing sector has suffered from dwindling stocks of traditional species as a result of dramatic changes in their availability. This has prompted fish technologists and the fish trade to pay more attention to aquaculture techniques as a source of fish and other seafood products (Stickney, 1990). Among cultivated fish, Coho salmon (Oncorhynchus kisutch), also called silver salmon, has received great attention because of its increasing production in countries like Chile, Japan and Canada (FAO, 2006a) in parallel to important capture production in countries such as USA, Russian Federation, Canada and Japan (FAO, 2006b). Most research on 3 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 this fish species has been carried out on genetic aspects and farming conditions during aquaculture production (Estay, Díaz, Neira, & García, 1997; Winkler, Bartley, & Díaz, 1999). However, previous research concerning quality changes produced during processing has been scarce, only accounting for freezing (Braddock & Dugan, 1972; Rodríguez, Losada, Larraín, Quitral, Vinagre, & Aubourg, 2007) and chilling (Barnett, Nelson, & Poysky, 1991; Aubourg, Quitral, Larraín, Rodríguez, Gómez, Maier, & Vinagre, 2007) conditions. The present study focuses on the employment of farmed fish species as raw material for the commercialisation of thermally-treated fish products. In it, Coho salmon was chosen, so that the effect of a short preliminary chilled storage on quality degradation in the resulting cooked product was studied through sensory, physical and chemical changes. Because temperature control is so important, an advanced biphasic chilling system in which slurry ice holds the fish at a lower temperature than traditional flake ice was employed as slaughtering and holding process (Yamada, Fukusako, & Kawanami, 2002). MATERIALS AND METHODS 18 19 Chilling system (slurry ice) elaboration 20 21 22 23 24 25 A slurry ice prototype (FLO–ICE, Kinarca S.A.U., Vigo, Spain) was used. The composition of the slurry ice binary mixture was 40 % ice/60 % water, prepared from filtered seawater (salinity: 3.3 %). The temperature of the slurry ice mixture was –1.5 ºC and the calculated salt content about 2.0%. The average temperature of the specimens was in the range of –1.0ºC to –1.5ºC. 4 Raw fish, chilling storage, sampling, cooking and chemicals 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Specimens of farmed Coho salmon (Oncorhynchus kisutch) (weight range: 2.83.2 kg) were obtained from Comercial Xanquéi (Lousame, La Coruña, Spain) in May 2006. Individual fish gonads were at the 4th/5th stage of Maier’s scale of gonad maturity. The fish were sacrificed at the cultivation plant by immersion in slurry ice. Individuals were kept under this chilling condition during transportation to the laboratory. Upon arrival in the laboratory, the fish specimens were neither headed nor gutted, but directly placed in an isothermal room at 2ºC and were surrounded by slurry ice at a 1:1 fish to ice ratio. The slurry ice mixture was renewed each three days of storage. During the chilled storage, once in a day a temperature logger was employed at different parts of the fish to monitor its temperature. Twenty-four hours after slaughtering, four individuals were not thermallytreated and were studied as initial raw fish (day 0). The remaining fish (12 individuals) were taken for the cooking process on days 0, 5, and 9 of chilled storage. Whole and ungutted salmon specimens were steam cooked during 25 minutes in our pilot plant (102-103ºC) to a final backbone temperature of 65ºC; the fish were then cooled at room temperature (15-18ºC) for about 2 hours. For each individual fish, the white muscle was then collected and splitted into three different parts. Two of them were directly employed for the sensory and physical analyses, respectively; the third one was homogenised and used for the chemical analyses. Both in raw and in cooked samples, each individual fish was studied separately from others to achieve the statistical study (n=4). Chemicals employed along the present work (solvents, reagents) were reagent grade (E. Merck; Darmstadt, Germany). 5 Composition analyses 1 2 3 4 5 6 7 8 9 10 11 Water content was determined by weight difference between the homogenised fish muscle (1-2 g) before and after 24 h at 105 ºC. Results are expressed as g water / 100 g muscle. The lipid fraction was extracted from the fish muscle by the Bligh and Dyer (1959) method. Quantification results are expressed as g lipid / 100 g muscle. NaCl contents were determined after boiling portions of fish muscle in the presence of HNO3, followed by the addition of excess 0.1N AgNO3 and the titration of non-neutralised silver nitrate with 0.1N NH4SCN (AOAC, 1990). The results are expressed as g NaCl / 100 g muscle. Volatile amine formation and pH assessment 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Total volatile base-nitrogen (TVB-N) values were measured by the Antonacopoulos (1960) method, with some modifications. Briefly, fish muscle (10 g) was extracted with 6% (w/v) perchloric acid and brought up to 50 ml, determining the TVB-N content –after steam-distillation of the acid extracts rendered alkaline to pH 13 with 2% (w/v) NaOH – by titration of the distillate with 10 mM HCl. The results are expressed as mg TVB-N / 100 g muscle. Trimethylamine-nitrogen (TMA-N) values were determined by means of the picrate method, as previously described (Tozawa, Erokibara, & Amano, 1971). This involves the preparation of a 5% (w/v) trichloroacetic acid extract of fish muscle. The results are expressed as mg TMA-N / 100 g muscle. The evolution of pH values in Coho salmon muscle was determined by means of a 6-mm diameter insertion electrode (Crison, Barcelona, Spain). 6 Lipid damage analysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Free fatty acid (FFA) content was determined by the Lowry and Tinsley (1976) method based on complex formation with cupric acetate-pyridine followed by spectrophotometric (715 nm) assessment. Results are expressed as g FFA / 100 g lipids. Primary lipid oxidation was determined by means of the peroxide value (PV) according to the ferric thiocyanate method (Chapman and McKay, 1949). The results are expressed as meq active oxygen / kg lipids. The anisidine value (AV) was determined in fish muscle according to the AOCS (1993) method, based on the reaction between αand β-unsaturated aldehydes (primarily 2-alkenals) and p-anisidine reagent. AV is expressed as 100 times the absorbance measured at 350 nm in a 1 cm path length cuvette from a solution containing 1 g lipid / 100 ml reaction medium. The thiobarbituric acid index (TBA-i) was determined according to Vyncke (1970). This method is based on the reaction between a trichloracetic extract of the fish muscle, and thiobarbituric acid at high temperature (95-97ºC), the resulting chromophore being measured at 532 nm. Results are expressed as mg malondialdehyde / kg fish muscle. Interaction compound formation 19 20 21 22 23 24 25 Formation of fluorescent compounds was determined with a Perkin Elmer LS 3B fluorimeter by measurements at 393/463 nm and 327/415 nm as previously described (Aubourg & Medina, 1997). The relative fluorescence (RF) was calculated as follows: RF = F/Fst, where F is the fluorescence measured at each excitation / emission maximum, and Fst is the fluorescence intensity of a quinine sulphate solution (1 µg / ml in 0.05 M H2SO4) at the corresponding wavelength. The fluorescence ratio (FR) was 7 1 2 3 4 5 6 7 8 calculated as the ratio between the two RF values: FR = RF393/463 nm / RF327/415 nm. The FR value was determined in the aqueous phase resulting from the lipid extraction of the fish muscle. Browning development was determined spectrophotometrically at 420 nm in the lipid extract of the edible flesh. The results were calculated using the equation: Browning = A x V / w, where A is the absorbance reading at 420 nm, V is the volume (ml) of the sample and w is the amount (mg) of the lipid sample. Textural analysis 9 10 11 12 13 14 15 16 17 18 A shear test was used to evaluate texture. Firmness and cohesivity were determined from a stress-distance curve obtained from a Universal Testing Machine (Lloyd Instruments Limited, LR-5K, Hampshire, United Kingdom) including a load cell of 500 N (Jonsson, Sigurgisladóttir, Hafsteinsson, & Kristbergsson, 2000). The shear force or firmness was measured as the maximum peak force (N) required to shear/cut through the samples; cohesivity was measured during the upward movement of the blade and was calculated as the deformation (mm) at maximum peak force (Sigurgisladóttir, Hafsteinsson, Jonsson, Nortvedt, Thomasses, & Torrisen, 1999). Sensory analysis 19 20 21 22 23 24 The analysis of rancid and putrid odour development was conducted by a sensory panel consisting of ten experienced judges, according to Howgate (1992). Panellists had been involved in sensory analysis of different kinds of fish foods during the last ten years. Previously to the present experiment, a special training was carried out concerning raw and cooked salmon of different quality conditions. 8 1 2 3 4 5 6 7 8 At each sampling time, the fish muscle portions were presented to panellists in individual trays and were scored individually. The panel members shared samples tested. Rancid and putrid odour developments were evaluated using a Quantitative Descriptive Analysis (QDA) on a non-structured linear scale with numerical scores from 0 (stage of no rancidity/ putridity at all) to 10 (stage where no increase in rancidity/ putridity is possible); score 5.0 was considered the borderline of fish acceptability. Scores among panellists were averaged. Statistical analyses 9 10 11 12 13 14 15 Data from the different measurements were subjected to one-way analysis of variance; comparison of means was performed using a least-square difference (LSD) method (Statsoft, 1994). A confidence interval at the 95% level (p<0.05) was considered in all cases. RESULTS AND DISCUSSION 16 17 Composition analyses 18 19 20 21 22 23 24 The water and lipid contents of cooked salmon were included in the ranges 68.20-73.70 and 1.80-3.10 g / 100 g wet muscle, respectively (Table 1). Values for both constituents did not result in significant differences as a result of the preliminary icing time; differences in mean values may be attributed to fish-to-fish variation. Lipid content of the white muscle showed to be relatively low; as an explanation, it can be argued that fish individuals employed in the present experiment correspond to the year 9 Sensory analysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 The rancid and putrid odour development was assessed in the cooked fish muscle. Results are shown in Figure 2. For both attributes, low scores obtained indicate a low rancid and putrid development, so that cooked fish can be considered as greatly accepted. No effect (p>0.05) of the previous chilling time could be assessed, according to the extended shelf life reported for salmon species under chilling conditions (Sveinsdóttir, Martinsdóttir, Hyldig, Jørgensen, & Kristbergsson, 2002). Among the different chemical parameters related to quality loss studied in the present experiment, amine formation (total and TMA) and secondary lipid oxidation compounds (AV and TBA-i) are known to be the most closely related to the formation of putrid and oxidised flavours, respectively (White, 1994; Olafsdóttir et al., 1997). Actual sensory scores on putrid odour development greatly agreed to the results obtained for volatile amine formation (Table 2). However, sensory scores on rancid odour development do not agree to secondary lipid oxidation values (AV and TBA-i) obtained for the different kinds of cooked samples. It is likely that an extended study considering longer previous chilling times would have given more information on the correlation of lipid oxidation and sensory descriptors. 16 REFERENCES 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Aitken, A., & Connell, J. (1979). Fish. In R. Priestley (Ed.), Effects of heating on food stuffs (pp. 219-254). London (UK): Applied Science Publishers Ltd. Alasalvar, C., Taylor, K., Öksüz, A., Garthwaite, T., Alexis, M., & Grigorakis, K. (2001). Freshness assessment of cultured sea bream (Sparus aurata) by chemical, physical and sensory methods. Food Chemistry, 72, 33-40. Antonacopoulos, N. (1960). Verbesserte Apparatus zur quantitativen Destillation wasserdampfflüchtiger Stoffe. Zeitschrift für Lebensmittel Untersuchung und Forschung, 13, 113-160. AOAC (1990). Official Methods of Analysis of the Association of Analytical Chemistry (15th ed). Va (USA): Arlington. AOCS (1993). Official Methods and Recommended Practices of the American Oils Chemists’ Society. 4th ed. (pp. 1-2), cd 18-19. Ashie, I., Smith, J., & Simpson, B. (1996). Spoilage and shelf-life extension of fresh fish and shellfish. Critical Reviews in Food Science and Nutrition, 36, 87-121. Aubourg, S. (1999). Review: Recent advances in assessment of marine lipid oxidation by using fluorescence. Journal of the American Oil Chemists’ Society, 76, 409419. Aubourg, S., & Medina, I. (1997). Quality differences assessment in canned sardine (Sardina pilchardus) by fluorescence detection. Journal of Agricultural and Food Chemistry, 45, 3617-3621. Aubourg, S., Medina, I., & Pérez-Martín, R. (1995). A comparison between conventional and fluorescence detection methods of cooking-induced damage to 17 tuna fish lipids. Zeitschrift für Lebensmittel Untersuchung und Forschung, 200, 252-255. 1 2 3 4 5 6 7 8 Aubourg, S., Quitral, V., Larraín, Mª A., Rodríguez, A., Gómez, J., Maier, L., & Vinagre, J. (2007). Autolytic degradation and microbiological activity in farmed Coho salmon (Oncorhynchus kisutch) during chilled storage. Food Chemistry, 104, 369-375. Barnett, H., Nelson, R., & Poysky, F.(1991).A comparative study using multiple indices to measure changes in quality of pink and Coho salmon during fresh and frozen storage. http://www.nwfsc.noaa.gov/publications/techmemos/tm208/tm208.pdf). NOAA Technical Memorandum NMFS F/NWC-208. U. S. Department of Commerce. 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Bligh, E., & Dyer, W. (1959). A rapid method of total extraction and purification. Canadian Journal of Biochemistry and Physiology, 37, 911-917. Braddock, R., & Dugan, L. (1972). Phospholipid changes in muscle from frozen stored lake Michigan Coho salmon. Journal of Food Science, 37, 426-429. Castrillón, A., Álvarez-Pontes, E., García, M., & Navarro P. (1996). Influence of frozen storage and defrosting on the chemical and nutritional quality of sardine (Clupea pilchardus). Journal of the Science of Food and Agriculture, 70, 29-34. Chapman, R., & McKay, J. (1949). The estimation of peroxides in fats and oils by the ferric thiocyanate method. Journal of the American Oil Chemists’ Society, 26, 360-363. Dondero, M., Cisternas, F., Carvajal, L., & Simpson, R. (2004). Changes in quality of vacuum-packed cold-smoked salmon (Salmo salar) as a function of storage temperature. Food Chemistry, 87, 543-550. 18 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Estay, F., Díaz, N., Neira, R., & García, X. (1997). Reproductive performance of cultured female Coho salmon in Chilli. Progress in Fish Cultivation, 59, 36-40. FAO (2006a). Fishery Statistics. Aquaculture Production. Yearbook 2004 (Vol. 98/2, p. 72). Rome (Italy): Food and Agriculture Organization of the United Nations. FAO (2006b). Fishery Statistics. Capture Production. Yearbook 2004 (Vol. 98/1, p. 109). Rome (Italy): Food and Agriculture Organization of the United Nations. Gallardo, J. M., Aubourg, S., & Pérez-Martín, R. (1989). Lipid classes and their fatty acids at different loci of albacore (Thunnus alalunga): Effects of the precooking. Journal of Agricultural and Food Chemistry, 37, 1060-1064. Gallardo, J., Pérez-Martín, R., Franco, J., Aubourg, S., & Sotelo, C. (1990). Changes in volatile bases and trimethylamine oxide during the canning of albacore (Thunnus alalunga). International Journal of Food Science and Technology, 25, 78-81. García-Arias, T., Sánchez-Muniz, J., Castrillón, A., & Navarro, P. (1994). White tuna canning, total fat, and fatty acid changes during processing and storage. Journal of Food Composition Analysis, 7, 119-130. Hardy, R., & Keay, J. (1972). Seasonal variation in the chemical composition of Cornish mackerel, Scomber scombrus (L.), with detailed reference to lipids. Journal of Food Technology, 7, 125-137. Hearn, T., Sgoutas, S., Sgoutas, D., & Hearn, J. (1987). Stability of polyunsaturated fatty acids after microwave cooking of fish. Journal of Food Science, 52, 14301431. Howgate, P. (1992). Codex review on inspection procedures for the sensory evaluation of fish and shellfish, CX/FFP, 92/14. 19 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Jonsson, A., Sigurgisladóttir, S., Hafsteinsson, H., & Kristbergsson, K. (2000). Textural properties of raw Atlantic salmon (Salmo salar) fillets measured by different methods in comparison to expressible moisture. Aquaculture Nutrition, 2, 1-9. Labuza, T. (1971). Kinetics of lipid oxidation in foods. CRC Critical Reviews in Food Technology, 2, 355-405. Losada, V., Piñeiro, C., Barros-Velázquez, J., & Aubourg, S. (2005). Inhibition of chemical changes related to freshness loss during storage of horse mackerel (Trachurus trachurus) in slurry ice. Food Chemistry, 93, 619-625. Lowry, R., & Tinsley, I. (1976). Rapid colorimetric determination of free fatty acids. Journal of the American Oil Chemists’ Society, 53, 470-472. McLay, R. (1982). Canning. In A. Aitken, I. Mackie, J. Merritt, & M. Windsor (Eds.), Fish: Handling and processing (pp. 115-125). Edinburgh (Scotland, UK): Ministry of Agriculture, Fisheries and Food, Torry Research Station. Olafsdóttir, G., Martinsdóttir, E., Oehlenschläger, J., Dalgaard, P., Jensen, B., Undeland, I., Mackie, I., Henehan, G., Nielsen, J., & Nilsen, H. (1997). Methods to evaluate fish freshness in research and industry. Trends in Food Science and Technology, 8, 258-265. Olafsdóttir, G., Nesvadba, P., di Natale, C., Careche, M., Oehlenschläger, J., Tryggvadóttir, S., Schubring, R., Kroeger, M., Heia, K., Esaiassen, M., Macagnano, A., & Jørgensen, B. (2004). Multisensor for fish quality determination. Trends in Food Science and Technology, 15, 258-265. Pigott, G., & Tucker, B. (1990). Seafood. Effects of Technology on Nutrition (pp. 104135). New York (USA) and Basel (Switzerland): Marcel Dekker, Inc. Pokorný, J. (1981). Browning from lipid-protein interactions. Progress in Food Nutrition and Science, 5, 421-428. 20 Rodríguez, A., Losada, V., Larraín, Mª A., Quitral, V., Vinagre, J., & Aubourg, S. (2007). Development of lipid changes related to quality loss during the frozen storage of farmed Coho salmon (Oncorhynchus kisutch). Journal of the American Oil Chemists’ Society. Accepted (Ref. J11389; DOI 10.1007/s11746007-1098-5). 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Roth, B., Johansen, S., Suontama, J., Kiessling, A., Leknes, O., Guldberg, B., & Handeland, S. (2005). Seasonal variation in flesh quality, comparison between large and small Atlantic salmon (Salmo salar) transferred into seawater as 0+ or 1+ smolts. Aquaculture, 250, 830-840. Seet, S., & Brown, D. (1983). Nutritional quality of raw, precooked and canned albacore tuna (Thunnus alalunga). Journal of Food Science, 48, 288-289. Sigurgisladóttir, S., Hafsteinsson, H., Jonsson, A., Nortvedt, R., Thomasses, M., & Torrisen, O. (1999). Textural properties of raw salmon fillets as related to sampling method. Journal of Food Science, 64, 99-104. Sikorski, Z., & Kolakowska, A. (1994). Changes in protein in frozen stored fish. In Z. Sikorski, B. Sun Pan, & F. Shahidi (Eds.), Seafood proteins (pp. 99-112). New York (USA): Chapman and Hall. Slabyj, B., & True, R. (1978). Effect of preprocess holding on the quality of canned Maine sardines. Journal of Food Science, 43, 1172-1176. Smith, J., Hardt, R., McDonald, I., & Templeton, J. (1980). The storage of herring (Clupea harengus) in ice, refrigerated sea water and at ambient temperature. Chemical and sensory assessment. Journal of the Science of Food and Agriculture, 31, 375-385. Statsoft (1994). Statistica for Macintosh: Statsoft and its licensors. Ok (USA): Tulsa. 21 Stickney, R. (1990). A global overview of aquaculture production. Food Reviews International, 6, 299-315. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Sveinsdóttir, K., Martinsdóttir, E., Hyldig, G., Jørgensen, B., & Kristbergsson, K. (2002). Application of quality index method (QIM) scheme in shelf-life study of farmed Atlantic salmon (Salmo salar). Journal of Food Science, 67, 1570-1579. Tozawa, H., Erokibara, K., & Amano, K. (1971). Proposed modification of Dyer’s method for trimethylamine determination in codfish. In R. Kreuzer (Ed.), Fish Inspection and Quality Control (pp. 187-190). London (UK): Fishing News Books Ltd. Vyncke, W. (1970). Direct determination of the thiobarbituric acid value in trichloracetic acid extracts of fish as a measure of oxidative rancidity. Fette, Seifen, Anstrichmittel, 72, 1084-1087. White, P. (1994). Conjugated diene, anisidine value and carbonyl value analyses. In K. Warner, & M. Eskin (Eds.) Methods to assess quality and stability of oils and fat-containing foods (pp. 159-178). Champaign Illinois (USA): AOCS Press. Whittle, K., Hardy, R., & Hobbs, G. (1990). Chilled fish and fishery products. In T. Gormley (Ed.), Chilled foods. The state of the art (pp. 87-116). New York (USA): Elsevier Applied Science. Winkler, F., Bartley, D., & Díaz, N. (1999). Genetic differences among year classes in a hatchery population of Coho salmon (Oncorhynchus kisutch) in Chile. Aquaculture, 173, 425-433. Yamada, M., Fukusako, S., & Kawanami, T. (2002). Performance analysis on the liquid-ice thermal storage system for optimum operation. International Journal of Refrigeration, 25, 267-277. 22 1 2 3 4 5 6 7 8 Yamamoto, Y., & Imose, K. (1989). Changes in fatty acid composition in sardines (Sardinops melanosticta) with cooking and refrigerated storage. Journal of Nutritional Science and Vitaminology, 35, 39-47. Acknowledgments 9 10 11 12 13 14 15 The authors thank Mr. Marcos Trigo for technical assistance, Comercial Xanquéi (Lousame, La Coruña, Spain) for providing the salmon fish and Kinarca S. A. U. (Vigo, Spain) for lending the slurry ice equipment. The work was realised in the frame of the Chilean University (Chile)-Consejo Superior de Investigaciones Científicas (Spain) Program (Project 2006 CL 0034) and founded by the Secretaría Xeral de I+D from the Xunta de Galicia (Galicia, Spain) (Project PGIDIT05TAL00701CT). 23 FIGURE LEGENDS 1 2 3 4 5 Figure 1: Textural (firmness and cohesivity) change detection in cooked salmon that was preliminary chilled during 0, 5, and 9 days* ( , respectively). 6 7 8 9 10 11 12 13 * Bars denote standard deviation of the mean (n=4). Figure 2: Odour (rancid and putrid) detection in cooked salmon that was preliminary chilled during 0, 5, and 9 days* ( , respectively). 14 15 16 17 18 19 20 21 * Bars denote standard deviation of the mean (n=4). 24 TABLE 1 1 2 3 4 5 Assessment of composition parameters* in raw and cooked salmon that was preliminary chilled Salmon sample (raw / cooked) Water content (g/ 100g muscle) Lipid content (g/ 100g muscle) NaCl content (g/ 100g muscle) Raw salmon 75.66 b (1.27) 2.46 (1.03) 0.07 a (0.01) Cooked salmon (0 days previous chilling) 70.37 a (2.11) 2.69 (0.41) 0.10 ab (0.04) Cooked salmon (5 days previous chilling) 72.66 a (0.94) 2.42 (0.49) 0.13 b (0.01) Cooked salmon (9 days previous chilling) 71.81 a (1.75) 2.31 (0.69) 0.21 c (0.01) 6 7 8 9 10 11 12 13 14 15 16 17 * Mean values of four independent determinations (n=4). Standard deviations are indicated in brackets. For each parameter, mean values followed by different letters (a, b, c) indicate significant (p<0.05) differences between the different kinds of samples. 25