CHANGES IN SHEATH PROPERTIES OF RAINBOW-TROUT EGGS DURING COLD AND FROZEN STORAGE

Rainbow trout eggs (V/VI Maier scale maturity stage) stored at 2 and -25-degrees-C were studied for hardness, lipid components, peroxides and conjugated diene and triene groups. The egg resistance to crushing after seven days of cold storage decreased from 87.3 to 66.0 g. The concentrates of free fatty acids, peroxides, diene and triene groups showed no tendency to increase. Changes in sheath resistance to crushing during frozen storage were significant. the resistance dropping from 87.3 to 30.0 g after 12 months of storage at -25-degrees-C. The temperature of -25-degrees-C inhibited lipolytic enzymes. Egg lipids were not oxidized before the third month of storage. After four months of storage at -25-degrees-C (hardness 46.5 g), the eggs were salted to determine the extent of hardness changes under the influence of sodium chloride solution and thermal treatment. Egg sheath hardness assays showed salting to result in hardness increasing from 46.5 to 85.0 g. Pasteurization reduced egg hardness, but the extent of reduction was not proportional to the duration of thermal treatment. Hardness reduction (down to 50.0 g) in the rainbow trout eggs during frozen storage has no detrimental effects on the suitability of eggs for delicatessen product manufacture.