FISH MUSCLE LIPOLYSIS—A REVIEW

Lipolysis occurs extensively in fish muscle post-mortem and is associated with quality deterioration in the frozen tissue. Fish muscle lipolysis is presented in the context of basic fish muscle physiology and lipid composition. Phospholipase A and lipases from fish muscle have been described and characterized. The reaction is usually followed by measurement of free fatty acid production, and several colorimetric assays are available. Processing and storage treatments have been shown to influence the extent and rate of lipolysis in fish muscle; most of the research in this area has been directed at the effects of frozen storage. The interaction of lipolysis and lipid oxidation is a particularly intriguing area of study as triglyceride hydrolysis leads to increased oxidation while phospholipid hydrolysis produces the opposite effect.     

A REVIEW OF SENSORY AND INSTRUMENTAL METHODS USED TO EVALUATE THE TEXTURE OF FISH MUSCLE

The texture of fish muscle is an important quality attribute that depends on several parameters, both intrinsic and extrinsic. Its evaluation by sensory means is the result of a combination of several parameters that cover every impression from when the fish first comes into contact with a surface in the mouth, until it is completely masticated. This makes texture difficult to describe and evaluate. In addition the muscle structure of fish is not homogenous, and this has important implications on texture measurements by instrumental means. Numerous instrumental and sensory methods have been used to evaluate the texture of fish and fish fillets, with varying results and there exists no universal recommended method.     

RELATIONSHIP OF pH AND TEMPERATURE TO DISRUPTION OF SPECIFIC MUSCLE PROTEINS AND ACTIVITY OF LYSOSOMAL PROTEASES

From a review of the literature, and from specific data presented in this paper, it was concluded that both postmortem temperature and pH have effects on meat tenderness and on disruption of specific myofibrillar proteins. Increased postmortem temperature porduces more tender muscles and increases the disruption of troponin-T, myosin, Z-lines, connectin and gap filaments. Elevated postmortem temperature also increases the activity of enzymes which cause the disruption of myofibrillar proteins. Higher ultimate postmortem pH (above 6.0) produces more tender muscle, but also produces dark-cutting meat Except for one experiment, lower pH in the first few hours postmortem (in muscle with normal ultimate pH; i.e., 5.8 or below) improves meat tenderness. High pH increases the activity of CAF and low pH increases the activity of lsosomal cathepsins. Both high and low pH increase the degradation of troponin-T, Z-lines, gap filaments and connectin, but the degradation of these proteins (except for Z-lines) is greater at a low pH. Low pH increases the degradation of myosin; conversely, high pH retards it degradation.     

TEXTURE OF FISH MUSCLE

Morphological and chemical aspects of fish muscle texture are reviewed and differences from red meat are pointed out. A unique feature of fish muscle is its low connective tissue content which accounts for easy disintegration of fish flesh on heating. Thus, the muscle fibers are the main textural elements in cooked fish meat. Because of this, most of the popular texture testing instruments are not applicable to fish. Best results are obtained with the thin blade shear/compression cell.
Texture of fish muscle is affected by the species, age and size of the fish within the species, and nutritional state. Postmortem factors influencing texture include glycolysis, rigor mortis and the accompanying contraction of the muscle often leading to the separation of muscle segments (gaping), temperature profile during storage, temperature of cooking, pH and presence of NaCl.     

CATHEPTIC ACTIVITY OF FISH MUSCLE

Catheptic activity was found to be localized in the lysosomal fraction of skeletal muscle of winter flounder (Pseudopleuronectes americanus). The enzyme hydrolyzed hemoglobin, globin, bovine serum albumin and endogenous proteins. The hemoglobin splitting activity of the enzyme under different conditions was determined by gel electrophoresis. An optimum pH of 4.0 was found for both the hemoglobin breakdown and autolytic activity on the endogenous proteins. The enzyme was highly thermostable, dialysis had no effect on its activity, and the enzyme was inhibited by sodium chloride, cysteine, ATP, NAD and phenyl methyl sulfonyl fluoride. Its molecular weight was found to be about 32,000 using sucrose gradient centrifugation.     

MARINE FISH DIGESTIVE PROTEASES—RELEVANCE TO FOOD INDUSTRY AND THE SOUTH-WEST ATLANTIC REGION—A REVIEW

The biological diversity of marine species provides a wide array of enzymes with unique properties. For this reason, there is great potential for the recovery and use of digestive proteases from fish provessing wastes. Fish digestive proteolytic enzymes most commonly studied include pepsin, trypsin, chymotrypsin, gastricsin and elastase. Enzymes from cold adapted ectothermic organisms have application in the food industry because their temperature and other characteristics differ from homologous proteases from warm-blooded animals. The South-West Atlantic ocean is an enormous reservoir of different fish species. The digestive proteases from these organisms can be isolated as a by-product and used for processing aids in the food industry.     

COMPARATIVE MICROSTRUCTURE OF RED MEAT, POULTRY AND FISH MUSCLE

Since muscle food researchers tend to focus on disciplines such as red meats, poultry or fish; there is little shared information across commodity lines. Comparisons among these three groups of muscle foods are discussed.     

FISH SAUCE PRODUCTS AND MANUFACTURING: A REVIEW

Fish sauce, due to its characteristic flavor and taste, is a popular condiment for cooking and dipping. Biochemically, fish sauce is salt-soluble protein in the form of amino acids and peptides. It is developed microbiologically with halophilic bacteria, which are principally responsible for flavor and aroma. This review article covers the manufacturing methods of fish sauce, factors affecting the quality of fish sauce, nutritional values of fish sauce, microorganisms involved with fermentation, and flavor. In addition, rapid fermentation to reduce time and new parameters to estimate the quality of fish sauce are reviewed. Along with a new approach for estimating the quality of fish sauce, the quantitative analysis of degradation compounds from ATP and other specific protein compounds in fish sauce are discussed.     

FISH SAUCE PRODUCTS AND MANUFACTURING: A REVIEW

Fish sauce, due to its characteristic flavor and taste, is a popular condiment for cooking and dipping. Biochemically, fish sauce is salt-soluble protein in the form of amino acids and peptides. It is developed microbiologically with halophilic bacteria, which are principally responsible for flavor and aroma. This review article covers the manufacturing methods of fish sauce, factors affecting the quality of fish sauce, nutritional values of fish sauce, microorganisms involved with fermentation, and flavor. In addition, rapid fermentation to reduce time and new parameters to estimate the quality of fish sauce are reviewed. Along with a new approach for estimating the quality of fish sauce, the quantitative analysis of degradation compounds from ATP and other specific protein compounds in fish sauce are discussed.     

A RESEARCH NOTE EFFECTS OF PRESSURIZATION AND REFRIGERATED STORAGE ON MICROSTRUCTURE OF FISH MUSCLE TISSUE

Fish muscle tissues were subjected to high hydrostatic pressures in the range of 1,000 - 3,000 atm and the tissues subsequently observed using transmission electron microscopy. Pressurization at 1,000 atm caused contraction of the sarcomere with the I-band thin filaments being lost while the A-band was unaffected. On pressurizing the tissues at 2,000 atm, the I-band region became more visible with breakdown of the thin filaments in this region as well as the Z-disks. There was gross disintegration ofmyofibrillar structure with collapse of A-band structure and T-tubular system on subjecting muscle tissue to 3,000 atm of pressure. However, there were no observable changes in myofibrillar structure beyond these initial changes during the subsequent 21 days of storage under refrigerated conditions (4–7C). The results provide the structural basis for pressure-induced changes in fish texture.     

海鱼鱼鳔资源利用研究

就海鱼鱼鳔的功能结构、营养与药用价值、食用和药用加工利用等现状进行了研究，并对海鱼鱼鳔资源的加工利用发展方向进行了探讨。     

海鱼鱼鳔资源利用研究

采用三氯氧磷（POCl3）对大豆分离蛋白（SPI）进行磷酸化改性,并研究了磷酸化前后SPI功能特性的变化.结果表明：磷酸化SPI的溶解性、乳化性以及粘度等功能特性都有不同程度的改变.     

HYDROXYL RADICAL MODIFICATION OF FISH MUSCLE PROTEINS

A xanthine oxidase-based system was used to generate hydroxyl free radicals in washed, minced cod muscle. Oxidation of protein was measured by increase in protein carbonyl content; the system used produced approximately 0.1 mol of carbonyl groups per 10⁵ g of protein. This degree of oxidation had only minor effects on the SDS-PAGE patterns of the muscle proteins. The solubility of the proteins was not affected by this amount of oxidation unless they were also subjected to a freeze/thaw cycle. With a freeze/thaw cycle, a highly significant decrease in protein solubility occurred compared to that which took place in a sample not exposed to the free radical system. Lowering the pH from 6.8 or 6.5 to 6.0 or 5.5 had a strong negative impact on protein solubility. Protein oxidation appeared in two phases in washed cod mince, an initial rapid increase followed by a second phase that may have been linked to oxidation of the small amount of lipid in the sample. Comparison of protein carbonyl formation in stored mackerel fillets or mince indicated that the range of oxidation studied in the cod model system was similar to what occurs in stored mackerel muscle postmortem.     

CHANGES DURING FERMENTATION AND PROPERTIES OF SOM-FUG PRODUCED FROM DIFFERENT MARINE FISH

ABSTRACT

Microbiological, chemical and physical changes of Som‐fug produced from six marine fish during fermentation were monitored. During the fermentation (0–72 h) at 30C, the increase in lactic acid bacteria (LAB) count and total acidity (TA) with the concomitant decrease in pH was observed. After the fermentation was completed, Som‐fug samples contained 1.5–7.9 × 10⁹ cfu/g LAB count and TA ranging from 2.00 to 2.28% with the pH range of 4.53–4.60. Trimethylamine N‐oxide content decreased, whereas trimethylamine content increased throughout the fermentation (P < 0.05). Proteolysis of Som‐fug proteins and lipid oxidation occurred during fermentation. As the fermentation proceeded, hardness, adhesiveness, springiness and cohesiveness of all samples increased, and L*, a*and b*values also increased (P < 0.05). Generally, Som‐fug produced from bigeye snapper showed a greater acceptability than those produced from other species. However, its acceptability was slightly lower than a commercial Som‐fug produced from freshwater fish (P < 0.05).

PRACTICAL APPLICATIONS

This research indicates that some marine fish can be used as the raw material for Som‐fug production with the quality almost comparable to those prepared from fresh water fish, which are commercially availalble. Therefore, the improvement of process for Som‐fug production from marine fish should be further conducted to obtain the better quality and higher acceptability. As a consequence, Som‐fug from marine fish with the high nutritive value can become a novel product for the consumers.

     

EFFECTS OF SALT AND SUCROSE ADDITION ON THERMAL DENATURATION AND AGGREGATION OF WATER-LEACHED FISH MUSCLE1

Heat-induced denaturation of water-leached fish muscle proteins, as affected by addition of sucrose and/or salt, were investigated by differential scanning calorimetry (DSC). Net enthalpic changes for these muscle proteins were always endothermic in nature, and of a greater magnitude at faster heating rates. This was interpreted to infer that aggregation at lower heating rates led to formation of a gel structure in which potential bondings were more completely accomplished; that is, a more energetically favorable structure was attained with slow heating. The stabilization of proteins by sucrose, and destablization of proteins by salt, were revealed by shifts in transition peaks and activation energies, the latter determined by two methods of kinetic analysis.