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

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. Moraxella species were predominant 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.     

LIQUID HOLDING CAPACITY AND INSTRUMENTAL AND SENSORY TEXTURE PROPERTIES OF HERRING (CLUPEA HARENGUS L.) RELATED TO BIOLOGICAL AND CHEMICAL PARAMETERS

Instrumental texture measurements done on raw herring fillets only partly describe the sensory texture of marinated herring fillets. Sensory texture parameters of marinated fillets were related to instrumental texture measurements of raw fillets by three different data analysis approaches. Uniaxial compression measurements were used as a single parameter, as compression curves or fitted to polynomials. Data from all three methods were related to sensory firmness (r = 0.310–0.366, P < 0.05). Elasticity could be predicted from the maximum compression force (r = 0.181, P < 0.05). The compression curve contained information correlating with all the measured sensory texture parameters (r = 0.102–0.310, P < 0.05), while the fitted polynomials, in addition to firmness, could predict fatty mouthfeel (r = 0.201, P < 0.05). The most information about the sensory texture was obtained from the compression curves. This study shows that the texture properties of herring are highly intercorrelated and can be regarded as a multivariate complex of parameters. The liquid holding capacity (LHC), defined as the moisture held after a low centrifuge speed expressible moisture measurement, and the texture of herring are influenced by a variety of factors, e.g., spawning time of year, gonad maturity, body size, age and lipid content (P < 0.05). Increases in body weight, age and lipid content are intercorrelated and result in marinated fillets being more firm, elastic, juicy and fatty. Decreases in these factors will give marinated fillets that are perceived to be gritty and with low intensities of firmness, elasticity, juiciness and fatty mouthfeel.     

CHARACTERIZATION OF SALMON (ONCORHYNCHUS KETA) AND STURGEON (ACIPENSER TRANSMONTANUS) CAVIAR PROTEINS

The solubility of protein components in salmon (Oncorhynchus keta) and sturgeon (Acipenser transmontanus) caviar in distilled water, 5% (w/v) NaCl, 70% (v/v) ethanol at 65C, and 0.2% (w/v) NaOH was determined. The salt soluble proteins were the predominant fraction and constituted 84.2% of the recovered protein in salmon and 86.1% in sturgeon samples. The two most prominent protein fractions (12.5% sodium dodecyl sulfate‐polyacrylamide gel electrophoresis) for sturgeon caviar are most likely vitellin (96 kDa) and ovomucoid or phosvitin (28 kDa). For salmon roe, small proteins, possibly lysozyme or phosvitin (10 kDa), are also present.     

PHYSICOCHEMICAL AND BIOCHEMICAL CHANGES IN WHOLE LIZARDFISH (SAURIDA MICROPECTORALIS) MUSCLES AND FILLETS DURING FROZEN STORAGE

The physicochemical and biochemical changes in whole lizardfish (Saurida micropectoralis) muscles and its fillets kept in air and under vacuum during frozen storage at ?20C for 24 weeks were investigated. The formaldehyde (FA) and dimethylamine contents increased with a concomitant decrease in trimethylamine‐ N‐oxide (TMAO) content as the storage time increased (P < 0.05). The Ca²⁺–adenosine 5′‐triphosphatase activity continuously decreased with a coincidental decrease in salt‐soluble fraction. The disulfide bonds were increasingly formed throughout the storage (P < 0.05). The surface hydrophobicity increased and reached the maximum at week 12 with a subsequent decrease up to the end of storage. In general, the higher changes were observed in samples kept under vacuum than those kept in air. With the same atmosphere used, the whole fish showed slightly higher changes than the fillets. A marked increase in TMAO demethylase (TMAOase) activities was observed up to 12 weeks, followed by the continuous decrease up to 24 weeks of storage. The produced FA might play an important role in inducing protein denaturation and/or aggregation in lizardfish. The TMAOase activity as well as the FA formation could be reduced to some extent with the removal of internal organs and storage in the presence of oxygen. However, a detrimental effect of oxygen, especially on the promotion of lipid oxidation, would be an obstacle.     

COMPARISON OF MARGIN OF SAFETY BETWEEN SENSORY SPOILAGE AND ONSET OF CLOSTRIDIUM BOTULINUM TOXIN DEVELOPMENT DURING STORAGE OF MODIFIED ATMOSPHERE (MA)-PACKAGED FRESH MARINE COD FILLETS WITH MA-PACKAGED AQUACULTURED FISH FILLETS

The margin of safety between shelf-life (onset of sensory spoilage) and potential time to toxin production by Clostridium botulinum type E in retail type packages of fresh marine cod fillets packaged in high barrier film under selected atmospheres [100% air, a modified atmosphere (MA) containing 75% CO₂:25% N₂, and vacuum] and stored under refrigeration (4C) and temperature-abuse conditions (8 and 16C) was investigated. Margin of safety data of MA-packaged marine cod fillets was also compared with MA-packaged aquacultured tilapia, catfish, and salmon fillets. Sensory spoilage preceded onset of toxin presence for the marine cod fillets packaged in any of the atmospheres and storage temperatures tested. At 4C, none of the marine cod fillets packaged in either atmosphere developed toxin, even 20 days after spoilage, as determined by sensory characteristics. During storage at refrigeration and mild (8C) temperature-abuse conditions, MA-packaged marine cod showed a greater margin of safety compared to aquacultured tilapia, catfish, and salmon packaged under the same atmospheres and conditions. Fat content appeared to potentially influence the margin of safety in MA-packaged aquacultured fresh fish fillets during storage.     

IDENTIFICATION AND CHARACTERIZATION OF THE MICROFLORA AND SPOILAGE BACTERIA IN FRESHWATER CRAYFISH Procambarus clarkii (Girard)

Crayfish tails were collected from two commercial peeling plants in South Louisiana and stored at 0° and 5°C. Initially and after various periods of storage, bacteria were isolated from the peeled tails, identified generically and subsequently classified on the basis of their ability to produce "spoilage" in sterile crayfish tail flesh. Micrococcus, Staphylococcus, Alcaligenes and Achromobacter were the predominant genera in the fresh samples of tails. Achromobacter predominated during early storage and Pseudomonas and Achromobacter were the dominating organisms in the spoiled tails. Of the 280 isolated bacteria, 22.1% were classified as "rapid spoilers," 16.4% were "slow spoilers" and 61.5% were "nonspoilers." Most of the spoilers were Pseudomonas , while an appreciable number belonged to Achromobacter.     

USE OF IMMERSION AND VACUUM IMPREGNATION IN MARINATED SALMON (SALMO SALAR) PRODUCTION

The kinetics of mass transfer during the production of marinated salmon were compared for the traditional dry processing method (D) and alternative processes involving immersion in ternary solution (sucrose and NaCl), both at atmospheric pressure (I) and with vacuum pulse (VI). The evolution of water activity, moisture, salt and sugar content and weight loss was measured during marination trials. Immersion marination (I and VI) processes reduced both the process time (approximately 85%) and the weight loss (approximately 48%), increasing yield.

PRACTICAL APPLICATIONS

The results of this article can be used by processing industries for the elaboration of salmon. The technologies of marinating salmon by immersion in ternary solution, with (IV) and without (I) vacuum pulse, have advantages in comparison with dry marinating technology. These are related principally to a reduction of processing time by 50% and of weight loss by 48%. Considering the growth of the production and consumption of salmon at a world level, we think that marinating technologies by immersion in an osmotic solution represent a good alternative to the industrialized production of marinated salmon.     

QUANTITATIVE EXTRACTION OF NUCLEOTIDES FROM FROZEN MUSCLE SAMPLES OF ATLANTIC SALMON (SALMO SALAR) AND RAINBOW TROUT (ONCORHYNCHUS MYKISS): EFFECTS OF TIME TAKEN TO SAMPLE AND EXTRACTION METHOD

Muscle excised from the dorsal flank of Atlantic salmon and rainbow trout at death and up to 120 min postmortem (P.M.) was frozen in liquid M₂ and stored at ‐80C. Following acid extraction, on ice (method 1), or dry ice (method 2) samples were analyzed for cyclic nucleotides to determine the effect of time to sample, and extraction method. There was no pattern of change in nucleotide profile in either species up to 10 min P.M. At 120 min P.M., Atlantic salmon muscle extracted by method 2 had a higher IMP concentration than at any other time but there was no difference in adenylates. Ignoring time taken to sample, method 2 resulted in higher adenylate and lower IMP concentration than method 1. These results indicate that method 2 is most effective in obtaining realistic nucleotide concentrations from fish muscle because it maintains the tissue temperature below the critical freeze zone, (‐0.8 to ‐5C) prior to enzyme inactivation.     

LIPID CHANGES IN FROZEN STORED FILLETS FROM PRE- AND POSTSPAWNED HAKE (MERLUCCIUS HUBBSI MARINI)

The lipid composition of frozen stored fillets from pre‐ and postspawned hake was studied. The total lipid (TL) content in the chloroform/methanol extract from unfrozen postspawned hake was four times higher than that of prespawned fish. After freezing, the TL content of postspawning hake muscle remained unchanged whereas the TL extracted from prespawning fish muscle increased about 90%. The TL extractability of muscle from fish in both different gonadal conditions was not affected by frozen storage. Lipolysis in frozen stored fillets from prespawned hake occurs principally by hydrolytic action on phospholipids (PL), and phosphatidylcholine was the main PL hydrolyzed. Triacylglycerols were the main substrates hydrolyzed in frozen stored fillets from postspawned hake. Freezing and frozen storage affected polyenoics and n‐3 fatty acids (FA). The decrease in the contents of n‐3 FA in fillets from postspawned hake was lower than that observed in fillets from prespawned fish.