Objective Methodology to Differentiate Between Fresh and Frozen-and-Thawed Meats

Abstract

Abstract : The basic knowledge that mitochondrial enzymes are released by freezing-and-thawing muscle tissue was used to develop a fairly simple objective test to distinguish between meat that has been frozen-and-thawed and that which has never been frozen. Previous studies indicate that glutamic-oxalacetic transaminase (GOT) of muscle press juice (MPJ) can be used for this. The test requires the determination of the relative amounts of mitochondrial isozyme (GOT(M)) and sarcoplasmic isozyme (GOT(S)) that is present in MPJ from the original meat sample of unknown history as received, and in MPJ from a portion of the original sample that has been intentionally frozen-and-thawed in the laboratory. Freezing-and-thawing does not alter the amount of (GOT(S)) in MPJ but increases the amount (GOT(M)) in the juice from 50-150% or more. The two isozymes are separated by electrophoresis and the relative amount of each isozyme present in the MPJ is determined by measuring its enzymatic activity. The values for percent GOT(M) in the MPJ's will be similar or show only a small increase if the unknown had been frozen. Over 140 muscle samples including samples of beef, pork, lamb chicken and turkey gave this result consistently.