The protein rest helps reduce these proteins. Other proteins formed during this time aid in head retention. Step 2 Starch conversion is mainly the work of two enzymes, alpha amylase and beta amylase. Beta amylase works better at lower temperatures and alpha amylase works better at higher temperatures. Beta amylase breaks starches into short chain sugars that are mostly fermentable.
Alpha amylase breaks starches into longer chain sugars and dextrins as well as short chain sugars.
Some of the longer chain sugars and dextrins are not fermentable and add body to our beer. This is the reason for the two target temperatures in starch conversion-raising the temperature at the end slows the work of the beta amylase, allowing some longer sugars to make it into our beer. Do not overadjust. If you've added a couple of teaspoons of either, and it still isn't in this range but is close, it'll work. Step 3 Mash out.