One of the main reasons a lot of homebrewers make the leap from extract to all-grain brewing is to have more control over the wort sugar profile. When we begin making our own wort, there are a handful of grain-native enzymes we can manipulate to influence the finished beer, but with today’s modern malts, we can put most of our attention on the “saccharifying” enzymes, alpha and beta amylase.
These two enzymes break down (hydrolyze) our grist’s amylopectin and amylose starches into smaller and more fermentable sugars, but they work in different ways. Alpha amylase cleaves these long starch chains somewhat indiscriminately into randomly smaller carbohydrates and is happiest in the 160–168°F (71–76°C) range. Beta amylase can work on only one end of the starch chain, prefers a temperature of 140–150°F (60–66°C), and falls apart (denatures) well before alpha amylase’s preferred temperature range. With a much more limited location of activity, beta amylase also works much more slowly than its alpha sibling. Luckily, there is enough overlap in the working ranges that we can expect good results by mashing in the 148–154°F (64–68°C) range, with the lower end giving us a bit more fermentable sugars than the higher end.
Let’s say that it’s brew day, and you’ve got your alpha amylase chopping those long starch chains up willy-nilly and your beta amylase nibbling the ends into fermentable sugars, working happily together at the low end of the normal mash range (148°F/64°C), and maybe you’re planning an extra twenty minutes of rest to make sure the job is complete. Great! You will definitely make beer, and it will likely be quite fermentable with a low finishing gravity, but there is more you can do!