At this point it leaves a limit dextrin and continues to chop maltose off the end of other dextrin chains. Alpha amylase breaks apart the long dextrins so there are more dextrin chains available for the beta amylase to work on from both ends. Each amylase has it's own preferred pH, but both will work efficiently between a pH of 5.2 and 5.7, although alpha amylase prefers the high side of this range and beta amylase prefers the low side. That's the science of saccharification. Now the art.
Yeast can only ferment maltose and simpler sugars.
More complex sugars will survive the fermentation and end up in the finished beer, lending flavor, color, aroma, body and head stability. Before we proceed, let's cover Gelatinization . Gelatinization is the process by which the starch matrix is broken up and dispersed into the mash solution. Only after entering the mash solution as starch kernels can the starch be acted upon by the amylase enzymes. This activity will produce an abundance of dextrin chains for the beta amylase to work on.