Muscle during frozen storage, protein

Owusu-Ansah, Y.L. and Hultin, H.O. 1987. Effect of in situ formaldehyde production on solubility and cross-linking of proteins of minced red hake muscle during frozen storage. Journal of Food Biochemistry 11 17-39. 

LeBlanc E. LeBlanc, R. Determination of hydrophobicity and reactive groups in proteins of cod (Gadus morhua) muscle during frozen storage. Food Chem. 1992, 43, 3—11. 

Jiang, S.T. Hwang, B.O. Tsao, CT. Protein denaturation and changes in nucleotides of fish muscle during frozen storage. J. Agric. Food Chem. 1987a, 35, 22-27. 

Torres-Arreola, W., Soto-Valdez, H., Peralta, E., Cardenas-Lopez, J.L. and Ezquerra-Brauer, J.M. (2007). Effect of a low-density polyethylene film containing butylated hydroxytoluene on hpid oxidation and protein quaUty of sierra fish (Scomberomorus sierra) muscle during frozen storage. Journal of Agricultural and Food Chemistry, 55,6140-6146. 

Sugar alcohols have also found application in foods containing sugars. Sorbitol is an effective cryoprotectant in surimi, preventing denaturation of the muscle protein during frozen storage. 

Chemical Deterioration of Muscle Proteins During Frozen Storage... 

Actomyosin. At high salt concentrations ( . . 0.6 M KC1), actin and myosin combine to form actomyosin filaments giving a highly viscous solution. Actomyosin retains the ATPase activity of myosin and demonstrates "super-precipitation" on the addition of ATP (24,34). As expected, there are differences between actomyosins of rabbit and fish with respect to solubility (10,22,35,36), viscosity (46) and ultracentrifugal behavior (477. Since actomyosin is the most readily available form of myofibrillar proteins from fish muscle, its behavior relative to deterioration during frozen storage has been most frequently studied. 

Information on the molecular changes occurring during frozen storage of whole muscle or of isolated protein preparations will be reviewed here. 

Among the above hypotheses, effects of lipids (4-17,59-62, 69-71,155-159), formaldehyde (160-166), and gas-solid interface TMJ appear to be very important in Gadoid fishes. Denaturation of myofibrillar proteins caused by free fatty acids and/or lipid peroxides must occur during frozen storage. To prove this, Jarenback and Liljemark have shown by electron microscopy that, in muscle stored frozen with added linoleic and linolenic hydroperoxides, myosin became resistant to extraction with salt solution (168). 

The concentrated salt solution may denature the proteins (9-17, 169-177). Whereas experiments with isolated muscle protein preparations cannot exclude the effects of salts such as NaCl or KC1 (since they are required to solubilize the proteins), denaturation during frozen storage has been decreased or prevented completely when an efficient cryoprotectant such as sodium glutamate or glucose was added (66,67,82,93,145-150). Hence, the effect of salts may not be of primary importance, though they may contribute. 

The water-activity relations, effects of displacements of water or effects of changes in the state of water must be the most important factors to trigger and to promote the denaturation of muscle proteins during frozen storage. 

As described by Fennema (9J, several refined hypotheses such as "physical barrier and structured water hypothesis" (134,178, 179), "ice-moderator hypothesis" (180-183), and "minimum cell volume hypothesis" (184) have been proposed. However, the author will take a more naive approach in interpreting the results on denaturation of muscle proteins during frozen storage at the same time taking advantage of the basic ideas of the above hypotheses. 

Actomyosin. Solubility. Studies have dealt with changes in the solubility of proteins during frozen storage of fish muscle or solutions of isolated actomyosin (33,51,52). Analysis by gel filtration of the salt extracts has shown that the actomyosin fraction decreases in solubility during frozen storage whereas the sarcoplasmic proteins remain essentially unchanged (53). 

Electron Microscopy. Examination of fish proteins by electron microscopy conclusively shows that actomyosin aggregates during frozen storage (59,63,69). The change in structures of the extracted myofibrillar proteins and of the myofibril residues of frozen-stored cod muscle was studied by electron microscopy. The decrease in the number of actomyosin filaments and an increase in the number and size of large aggregate were found (69). Unfrozen carp actomyosin, either dissolved in 0.6M KC1 or suspended in 0.05M KC1, exists in a typical arrowhead... 

Other Proteins. Since Reay and Dyer discovered that denaturation of myofibrillar proteins is of such profound importance, little attention has been given to the water-soluble proteins including enzymes and other proteins in the sarcoplasm, subcellular organelles, and cell membranes. Recently reports have appeared on the freeze denaturation of enzymes. These studies involved enzymes such as catalase, ADH, GDH, LDH, and MDH from sources other than fish (88,89,90) and attention was given to the effectiveness of various cryoprotective substances (89, 90). Comparable studies with enzymes from fish muscle are few in number (91). Studies on fish muscle proteins must be extended to this area if a complete picture of the freeze denaturation of fish muscle is to be obtained. It should be noted that freeze stable enzymes might have important effects during frozen storage of fish (92,93). 

Benjakul, S., Visessanguan, W., Thongkaew, C., and Tanaka, M. 2003a. Comparative study on physicochemical changes of muscle proteins from some tropical fish during frozen storage. Food Research International 36 787-795. 

Farouk, M.M. and Swan, J.E. 1998. Effect of muscle condition before freezing and simulated chemical changes during frozen storage on protein functionality in beef, Meat Sci., 50, 235. 

Rehbein, H. 1985. Does formaldehyde form crosslinks between myofibrillar proteins during frozen storage of fish muscle Sci. Tech. Froid 4 93-99 cited in Chem. Abstr. CA 106(7) 48808d. 

Kjnrsgard JVH, Nprrelykke MR, Jessen F (2006). Changes in cod muscle proteins during frozen storage hy proteome analysis and multivariate data analysis. Proteomics, 6 1606-1618. 

Lipid oxidation in subcellular fractions can be mediated by enzyme systems in muscle microsomes that maintain iron in the ferrous form by reduced nicotinamide adenine dinucleotide (NADH). However, this redox system may not be enzymatic because, unlike lipoxygenase, no specific lipid oxidation products have been identified. Ascorbate and other reducing agents may have the same effects in the presence of heme-protein complexes. On the other hand, the presence of 15-lipoxygenase in chicken muscle may be responsible for oxidative deteriorations in uncooked chicken meat during frozen storage. Phospholipases... 

FIGURE 9.1 Scheme for denaturation and aggregation of muscle proteins during freezing and frozen storage. 

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