Quantitative extraction of nucleotides from frozen muscle samples of Atlantic salmon ( Salmo salar ) and rainbow trout ( Oncorhynchus mykiss ) : Effects of time taken to sample and extraction method

Muscle excised from the dorsal flank of Atlantic salmon and rainbow trout at death and up to 120 min postmortem (P.M.) was frozen in liquid N-2 and stored at -80C. Following acid extraction, on ice (method I), or dry ice (method 2) samples were analyzed for cyclic nucleotides to determine the effect of time to sample, and extraction method. There was no pattern of change in nucleotide profile in either species up to 10 min P.M. At 120 min P.M., Atlantic salmon muscle extracted by method 2 had a higher IMP concentration than at any other time but there was no difference in adenylates. Ignoring time taken to sample, method 2 resulted in higher adenylate and lower IMP concentration than method I. These results indicate that method 2 is most effective in obtaining realistic nucleotide concentrations from fish muscle because it maintains the tissue temperature below the critical freeze zone, (-0.8 to -5C) prior to enzyme inactivation.