When something denatures I thought it trying to refold back to it's original form but once it's denatured the unfolded proteins cannot form exactly back to it's original form therefor always denatured? I could be wrong what do U mean by re nature ?
You're not far off here. Spontaneous protein renaturation can occur, but certainly not in the sense that denatured food proteins simply refold back to their original forms after the external stressor (e.g. heat, radiation, strong base or acid) has been halted or removed. Some equate denaturation with a complete lack of protein bioavailability which is also incorrect, although very high heat can render small percentages unusable namely due to the impact on lysine, glutamine, and cystine. Regarding your original question, flash pasteurization (which I believe typically occurs near 160F) will result in denaturation, but that should have a minimal impact on bioavailability.