When mash is rested at high temperature the final product is close to homemade American Style Malt Liquor. 158F is the temperature dead center of Alpha II and Alpha I action. It is the temperature used when malt is being tested in the malt house for Alpha action. When Alpha liquefies amylose (simple starch chain), liquefication occurs at what is called a 1-4 link. When the link is liquefied, the chain is severed and two chains are formed. The one chain is called the reducing end and the other chain is called the non-reducing end. The reducing end can be further liquefied by Alpha to a certain point and when that point is reached, non-fermentable sugar is dumped out and randomly, A-limit dextrin can form. That is the non-fermentable part of Alpha.
Then, there is the non-reducing end. It is called the non-reducing end because Alpha cannot liquefy it. The non-reducing end is glucose, it is the inherent sugar and glucose is fermentable. When Alpha liquefies the starch chain, saccharification occurs. When Alpha gelatinizes amylo-pectin (complex starch chain), dextrinization occurs. Amylo-pectin is responsible for adding body in beer and at 158F hard starch does not burst.
Beta is the other enzyme and it works on the non-reducing end formed after Alpha liquefies the starch chain. Beta chops off two chunks of glucose from the non-reducing end and mixes the chunks with a chunk of water and maltose is formed. That is where the term conversion comes into play. Beta converts glucose into maltose. At a high temperature of 158F, Beta denatures quickly, limiting conversion. Fermentation will be primarily due to glucose. When there is maltose in the mixture, the fermentation cycle is steady, even, and takes a little longer.
