ABSTRACT
Samples of bovine muscle were frozen at -5 degrees, -10 degrees, -20 degrees, -40 degrees, -60 degreese, -80 degreese, and -196 degrees C at slow (about 1 degrees/10 min) and high freezing rate (maximum 1 degrres/0.05 min) and subsequently thawed at room temerature. The changes in the extractable activity ("total activity") of the enzymes aconitase (AC), fumarase (FU) succine dehydrogenase (SDH), glutamic oxaloacetic transaminase (GOT), the mitochondrial isozyme of the COT (GOTM) and glutamate pyruvate transaminase (GPT) by freezing and thawing were studied. Neither the temperature nor the rate of freezing influenced the total activity of these enzymes. The subcellular distribution of these enzymes was investigated by determination of the enzyme activities in the muscle press juice. Freezing at -5 degrees C hat only little influence, but between -10 degrees and -40 degrees or -60 degrees C the release of AC, FU, GOTM and GPT from the mitochondria into the sarcoplasma increased with falling temperature, apparently by increasing damage of the mitochondria. The extent of this effect was not significantly influenced by the rat of freezing. Between -60 degrees and -196 degrees C no further rise of this effect was observed. A release of SDH did not occur at all conditions of freezing. It is suggested that the damage of muscle mitochondria by freezing and thawing is mainly due to a dehydration process.
