549349 Sat Aug 16 23:15:12 -0700 2008 2 31 Home Cooking 0 3963356 If you marinate something in unripeded papaya puree to tenderize it, you are not supposed to refrigerate it because the enzymes that break down the meat fibers stop working at cold temperatures. Suppose I don't have easy access to green papayas so when I find them, I want to puree them in small portions and freeze these for later use. Will freezing kill the papain enzymes or will they come back to life and work as a tenderizer when I defrost it? Sat Aug 16 23:15:16 -0700 2008 118120 luckyfatima 1 3963486 The enzymes are catalysts, chemical compounds that accelerate a chemical reaction but do not take part in it. They are not living organisms, though I believe they are proteins. A chemist out there may want to correct me. Temperature does affect them, however. Many are denatured by cooking temperatures approaching boiling, but I have not heard that cold does it. Try it and see. You can also buy dried papayin in health food stores--it is the ingredient in many meat tenderizers. Sun Aug 17 04:20:39 -0700 2008 3963356 53369 Father Kitchen 2 3965303 Enzymes are deactivated by heat, though IIRC, papain is one that can go pretty high in temp -- up to 140 degrees F or so -- and stay working. Don't know if papain dies in cold...you might experiment with this. Some commercial papaya products are made by companies blast-freezing the fruit, but if any enzyme remains intact and can be "re-energized" I don't know. It's quite powerful as a tenderizer, and like all enzymes dies quickly in acidic environments. Yes, enzymes are proteins, and they cause reactions in other proteins. Mon Aug 18 00:58:42 -0700 2008 3963486 18222 maria lorraine