tough old venison sousvide time/temp

pldurand

An acquittance asked me about cooking an old tough piece of venison sous vide. I suggested 135F for 72 hours based on my experience with beef ribs. He came back with the following question:

"How does that work? Collagen begins to break down when the internal
temp of meat reaches at least 170F. If the circulator maintains an even
temp that is less than 170F, how does a tough cut of meat ever become
tender?"

I tried to look up the answer in Modernist Cuisine but was unable to find an explanation. The beef ribs that I cook turn out medium rare and quite tender, so it does work. Now it has me wondering why.

I appreciate your help.

Cheers,
Peter

Chris_Young_80640

Cookbooks and some scientific sources commonly claim that collagen converts to gelatin “at” some particular temperature. Usually the cited threshold lies between 140 °F and 170 °F. In reality, the hydrolysis of collagen is simply another example of a chemical reaction whose rate varies exponentially with temperature. The exact reaction rate for collagen hydrolysis depends on the specific attributes of the collagen, which in turn depend on the cut, breed, and age of the animal it came from.

The reaction rate is so strongly linked to temperature that at low temperatures it might not seem to occur at all. If, for example, the reaction speeds up by a factor of four when the temperature increases 20 °F, then it would take 48 hours at 130 °F to achieve the same amount of collagen breakdown that would result from three hours of cooking at 170 °F. A cook who tried heating the meat to 130 °F for a short time might notice the small amount of conversion and conclude that the reaction does not happen at that temperature. But it does.