In all-grain brewing, mashing is the most customizable part of the brewing process. Whether you use a single mash infusion, a stepping mash or a decoction mash, the goal of mashing is the same in most cases, to get out the fermentable sugars and malt extract into your brew. If you use one method and you make good tasty beer stick with it. This is just a little lesson on some of the reasons you are doing what you are doing in your mash.
There are two main players in your mash that will assist you in extracting sugars from the grains. They are the Alpha and Beta amylase. Now these are some weird words but in general you can think of them as the two main sugar detaching and converting components you need for a good finished beer. Each of them is produced more readily at different temperatures. The Alpha-amylase is active at higher temperatures between 150-165 degrees. Beta-amylase is more active from 140-155 degrees or so.
The difference between the two is that the Alpha- amylase are more capable at converting starches into sugars, and then some of those sugars into fermentable sugars. The Beta-amylase are really only good at breaking down sugars into fermentable sugars. Together they make the perfect team to convert those starchy grains to fermentable sugars. You want to have roughly even amounts of each because the unconverted sugars and starches will add flavor and body to your beer and too many of one or the other can throw the beer off.
Fermentable sugars are definitely the goal for a home brewer. If you spend too much time at the higher temperatures you will have a lot of sugars in your mash but they will all be long chain sugars that yeast cells don’t like to eat. If this does happen you will end up with a sweet beer that won’t attenuate (or ferment to completion) as well as you had hoped. Also resulting in a low alcohol beer (and who wants that to happen 🙂 ). This is why we need the Beta’s to come in and strip these long sugars of a few bonds to make them more appealing to the yeast. Too many Beta-amylase can also be undesirable because too many can convert all the sugars to fermentable sugars, resulting in a dry alcohol tasting beer. The trick is to get a balance of each to be able to achieve a balanced brew.
Even though alpha and beta amylase are the two main players in this process, there are many other players as well. Step mashing from low temperatures to hit all of the sugar converting compounds is also an option. But with today’s highly modified malts it is becoming less and less necessary to hit all of these other temperatures.
So keep in mind the next time you brew a beer. If the beer turns out a little sweet and your yeast seemed to have performed flawlessly you may have mashed a little hot creating too many non-fermentable sugars that the Beta-amylase could not convert. If your beer is dry and alcohol tasting, you may have mashed too at too low of temps. These are just a few more things to think about when diagnosing your beer, hopefully making you a better brewer in the end.