Originally Posted by r_flagg
I'm doing my first AG batch this weekend - a witbier from Northern Brewer. I read their promash readout which recommends a protein rest btwn. 122-133*F, saccharification at 154* and mashout at 170*. It seems a step mash is recommended for a witbier, as it needs excellent head retention and cloudiness. I read that protein rest at 133* is better for head retention and cloudiness by keeping the protein strands at a medium size instead of chopping them down to smaller bits like it would at 122*. Any truth to any of that?
Protein rest temps and proteolytic enzymes don't work quite like that. There are conditions that are ideal for proteolytic enzymes including a specific temperature range. These enzymes will break down proteins period... not just ones of a certain size.
So it all depends on how much of what size proteins are already in your malt. If the ratio of soluble proteins to insoluble proteins is relatively high (this is called the soluble nitrogen ratio, or SNR), the less of the need for a protein rest and, in fact, doing one could hurt your mouthfeel and head retention.
Protein rest times and temps can be adjusted to get more or less breakdown of proteins. So, if you wanted to do a minimal protein rest, you could either do a very short rest in the typical temp range, or do a longer rest in the range between protein rest temps and saccharification rest temps.
So that's some general info on protein rests. For your specific issue, if you held a protein rest at 133°F for a long enough time, you would break any size proteins down more than you intended... large, medium, and small. As for protein rests with wheat beers, better let someone with more wheat experience answer your question, as I've only brewed with wheat malt once. Or do a search as I know this has been discussed before.