Accelerated Nucleotide Degradation and Glycolysis During Warming to and Subsequent Storage at −5 C of Prerigor, Quick-frozen Adductor Muscle of the Sea Scallop (Placopecten magellanicus)

During slow warming of prerigor, quick-frozen scallop meats from −26 to −5 C, arginine phosphate and ATP were split rapidly between −8 and −6 C (in about 2 h), resulting in the accumulation of some ADP, and of large amounts of AMP, equivalent to 85% of the ATP originally present. Concomitant activation of glycolysis caused a substantial increase in fructose 1,6-diphosphate (FDP) concentrations, and smaller increases in the hexose monophosphates (HMP) and in octopine. The relatively low freezing point of prerigor scallop muscle, found to be −1.4 C, may be implicated in the stimulation of metabolic activity at a temperature as low as −5 C; the rates were faster than at 0 C and occurred at subfreezing temperatures considerably lower than those for most fish muscle.With continued storage at −5, FDP decreased as HMP concentrations rose sharply to maximum levels at 24 h; octopine accumulation was slower, attaining maximum concentrations at 5 wk. Rates of AMP degradation and of hypoxanthine accumulation were similar to those in unfrozen, iced scallop muscle, indicative of differential effects of temperature on the various metabolic enzymes.Because of the extensive metabolic activity in scallop muscle at temperatures near −5, the optimal quality of prerigor quick-frozen meats may be affected adversely by current commercial distribution and marketing practices where warming to temperatures just below the freezing point may be encountered.