Just my speculation here. Prions seem to need some sort of template to guide their folding as well as the cooperation of chaperone proteins. https://en.wikipedia.org/wiki/Prion I would suspect that denaturing, and potential re-folding, of proteins during cooking would be rather random. So even if one, or very few, copies of a potential prion happened to be produced, the high temperatures, rapid pace of denaturation and the lack of chaperone proteins would not allow the formation of meaningful amount of potential prions to cause disease. Add to that the doubtful chance a prion would be produced in the first place, due to the lack of the usual physiological conditions and participants, feel free to eat cooked food!