Frozen storage activity during

Wastewater samples have usually been collected in precleaned amber glass containers. Both discrete and composite samples have been used for the analysis of effluents and influents of WWTPs. Unpreserved samples are normally stored at 4 °C for 48 h, or frozen [48]. Other authors add chemical agents such as methanol, sulfuric acid, or mercuric chloride to prevent bacterial activity during storage, and/or store the samples in supports used for extraction [26,35,57]. 

Soluble solids uptake due to osmotic dehydration, in addition to improving color, aroma, and vitamin stability during both air drying and frozen storage, could also play a very important role in the preparation of new types of ingredients at reduced water activity (Torreggiani et al., 1988). Due to the... 

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. 

When 0.1 M sodium glutamate was added to carp actomyosin, denaturation during frozen storage was almost eliminated, as measured by changes in solubility, viscosity, ultracentrifugal behavior, ATPase activity and electron microscopic profiles (66,72) (Figure 3). This protective effect of sodium glutamate will be discussed below. 

Changes in solubility, viscosity, ATPase activity, and ultracentrifugal and salting-out profiles were found during frozen storage at -20°C of carp myosin solutions (in 0.6 M KC1) and carp myosin suspensions (in 0.05 M KC1) (82,93). 

Figure 7. Decrease of LDH activity during frozen storage for 16 hours at —20°C, in the absence and presence of 0.2M sodium glutamate., no additives -0-, 0.2M sodium glutamate added (122).

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. 

In 1975, the U.S. Department of Agriculture (7) recommended that, for the majority of vegetables, catalase inactivation was not a satisfactory predictor of storage stability and that inactivation of peroxidase was necessary to minimize deterioration of quality during frozen storage. Use of peroxidase as the indicator is not without problems as it can recover its activity under certain conditions (8, 9). With the exception of asparagus, there is no evidence that peroxidase is directly associated with quality deterioration in most plant materials. 

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