Objective Methodology to Differentiate Between Fresh and Frozen-and-Thawed Meats
Final rept. 23 Jun 1973-30 Jun 1974
WESTERN REGIONAL RESEARCH CENTER BERKELEY CA
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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 GOTM and sarcoplasmic isozyme GOTS 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 GOTS in MPJ but increases the amount GOTM 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 GOTM in the MPJs 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.
- Food, Food Service and Nutrition