Frozen storage proteins during

Sych, J., Lacroix, C., Adambounou, L. T., Castaigne, F. (1990). Cryoprotective effect of lactitol, palatinit and polydextrose on cod surimi proteins during frozen storage. J. Food Sci, 55, 356-360. 

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. 

The effect of cooking on incurred residues of oxfendazole in cattle liver has been also investigated (88). However, the results drawn from this study are inconclusive due to several variable factors. One such factor is the unstable equilibrium between oxfendazole, oxfendazole sulfone, and fenbendazole in the incurred tissue. Other factor is the overall instability of oxfendazole and its metabolites in tissue during frozen storage. Another factor is the variable distribution of the residues within the tissue used for the study and the effect of protein binding on the extractability of the residues from the tissue. It was nevertheless... 

Khan, M. A. A., Hossain, M. A., Hara, K., Osatomi, K., Ishihara, T., and Nozaki, Y. 2003. Effect of enzymatic fish-scrap protein hydrolysate on gel-forming ability and denaturation of lizard fish Saurida wanieso surimi during frozen storage. Fish. Sci., 69,1271-1280. 

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. 

The above mentioned dissociation of actomyosin into actin and myosin could be due to a shift in the equilibrium, actomyosin 5= actin + myosin, by the highly concentrated salt solution of the unfrozen liquid portion in the protein-water system (22, 77). However, if this is true, the dissociated actin and myosin must re-associate immediately after thawing. This may be difficult since the ability to associate is decreased during frozen storage. 

Tropomyosin and troponin. Tropomyosin is apparently the most stable of the fish fibrillar proteins during frozen storage. It can be extracted long after actin and myosin become inextract-able however, it does denature gradually (90). 

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. 

Figure 9. A schematic model of denaturation of a-helical proteins during frozen storage and its prevention by cryoprotectants. The case with dianionic cryopro-...

Figure 6. The insolubitization of soybean protein during frozen storage at —5°C and their solubility behavior in urea and mercaptoethanol (ME) (10).

Japanese Society of Food Science and Technology Figure 13. Comparison of rates of insolubilization during frozen storage between soybean protein solutions frozen immediately after preparation (heated and unheated) and frozen after 2 days of storage (heated and unheated). The heated samples were held at 100°C for 5 min prior to freezing ( ll). 

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