> I have a few general questions for anyone. I know cooking food kills enzymes, > but what about freezing foods? Like having an occassional frozen banana or > frozen grapes for dessert. If freezing simply diminishes the enzyme content, > is it significant, or does it vary per food/time frozen/temp? I have no sspecific answer about enzymes in bananas, but generally, enzyme activity is decreased by freezing and thawing, but the effects of freezing and thawing depend on the enzyme. ----------------------------------------------------------------- Pearce RE, et al., Effects of freezing, thawing, and storing human liver microsomes on cytochrome P450 activity, Arch Biochem Biophys. 1996 Jul 15; 331(2): 145-169. Microsomes from five human livers were prepared from fresh (unfrozen) tissue and from tissue that was stored frozen at -80 degrees C for 1, 2, 4, or 6 months. The apparent concentration of cytochromes P450 and b5 and the activity of NADPH-cytochrome c reductase decreased 20-40% as a result of freezing the liver, regardless of whether the liver was stored for 1 or 6 months. ------------------------------------------------------------------ El-Badawi AA, Hamm R, Influence of temperature and rate of freezing of bovine muscle on the subcellular distribution of some mitochondrial enzyme, Z Lebensm Unters Forsch. 1976 Nov 24; 162(3): 217-226. Samples of bovine muscle were frozen at -5 degrees, -10 degrees, -20 degrees, -40 degrees, -60 degrees, -80 degrees, 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.