I agree with Denny and the others that 99% of the time you will do more harm than good with any protein rest. As stated if you feel its warranted 131>is sound advice.
70% of today’s malts are considered well modified and contain low protein levels.
If you employ a protein rest you start to create extra low mouthfeel/ body and affect head/ foam
25% of todays malts are considered overmodified and the mash should actually be adjusted to add more dextrins as the beer produced with extreme overmodified malt will be thin in body naturally if only rested within 140-150(ish).
5% > The only time to employ protein rests is if using undermodified malt which is very rare unless you seek it out. With large % of grist containing six row malts, rye, oats or other containing high protein levels or when using high percentages of adjunct like rice, corn etc… in the grist. Or large amounts of sugars in the wort boil as you want to increase the FAN levels then as the adjuncts dilute the FAN pool.
By employing protein rests with well-over modified malts other than creating poor body and low foam positive factors. You potentially create an excess of FAN with normal well-overmodified malts. Which we know low FAN is suboptimal and will see yeast stressed thus creating excess higher alcohols or long lag times etc…, midrange levels created by normal Sacc rests alone is perfect in today’s malts, whereas high-extreme levels of FAN can actually help the yeast to create excess diacetyl and other higher alcohols/ Fusels the same as if they had low FAN.
