To those of us who’ve never brewed, the process can seem a bit mysterious. We know that grain is involved, and that yeast converts sugar into alcohol and CO2. Beyond those two data points, most everything is an unknown.
Previously I’ve discussed grain, yeast, and even hops. Now is the time when we start putting these things all together. First up? The mash.
Wait, wait, hold on a second. Okay, before the mash, I should say that I hadn’t yet talked about water. The type of water does play a crucial role in brewing, particularly when one starts thinking about pH levels, acidity, and alkalinity. But I’ll go into more detail on that next week sometime. Let’s just presume that you’re using water from Plzeň in the Czech Republic (birthplace of the pilsner, and famous for its very soft water).
When you think mash, think breakfast oatmeal. Although brewing uses malted grain in place of the oatmeal, the premise is still basically the same. You take a bunch of grain, add some water, and then cook it. Anyone who has ever made oatmeal will know that the water turns into a thick, hazy, oat-y liquid that’s quite viscous, and very definately has a higher gravity than pure H20. That liquid, if we were to be making a beer, would eventually become the wort.
Now this explanation is a massive simplification, because while a breakfast patron only has to worry about getting their oatmeal hot, the brewer has a plethora of other variables to take into consideration. For one, a brewer would use malt in place of the oatmeal, and the malt should have far more starch readily available to be converted into sugar. But before even getting to that part of the process, two other moments have to be watched for.
The brewer is very keen on temperature of their mash, for important things happen at different temperatures, moments that can be controlled by the brewer to help shape the type of beer they wish to develop. For example (Warning! Organic chemistry ahead!):
95-120°F: The Acid Rest
When the temperature of the mash gets to this point, the phytase enzyme found in the malt breaks down phytin into …wait for it…phytic acid. This acid helps lower the pH level of the mash, reducing its alkalinity. Each variety of beer has an optimal pH level, and a good brewer will be able to deduce the effect of the acid rest that will give them the best chance of reaching that level.
Additionally, this temperature range also initiates the beta-glucanase enzymes. These enzymes go a long way to removing and diluting the gluey, sticky properties that come from using certain grain sets, including rye, oatmeal, and even six-row barley. To further the oatmeal analogy, the mash should not end up with, or have reduced amounts of big, sticky clumps of cooked grain.
113-127°F: The Protein Rest
Yeast also has optimal eating conditions, and the mash can be controlled to reach those conditions. Mostly this comes down to molecular weights. Before getting to this temperature, the proteins in the mash have molecular weightd of between 17,000-150,000. Then the proteinase enzymes are kicked into gear at these temperatures, and enter into proteolysis, b breaking down the higher weighted proteins into smaller polypeptides, which in turn are also broken down by peptidase enzymes into peptides and amino acids. Two things result from this. This is a another hit of acid that lowers the pH levels, and further into the process, this enzymatic conversion will encourage both yeast nutrition, and even longer head retention in the final product.
Again, the amount of enzymatic conversion will be dictated by the type of beer one wants. For example, a light lager, where head retention is not so important, will probably spend less time on a protein rest, while a Belgian Brown Ale will have particular interest in getting this right.
130-148°F: Starch Conversion (beta amylase)
Starch conversion is the critical part of the mash, and temperature variations here can be the difference between a strong but weak tasting beer, versus a flavorful one with a low alcohol content. A brewer needs to pay strict attention to these temperatures (again, depending upon the type of beer they wish to make).
First up is the beta amylase (noted as β-Amylase), an enzyme that converts starch into sugar in a very ordered manner. Think of beta-amylase as the neat, anal retentive enzyme that breaks down starch molecules in a straight line, much in the way that Pac-Man eats pellets. When the beta amylase enzyme is done, there are one or two molecule-structure sized sugars about, making them ripe pickings for the yeast to chow on later on. In fact, if you want to end up with a very fermentable wort, you focus on the temperature range for the beta-amylase.
152-158°F: Starch Conversion (alpha amylase)
Beta-amylase’s brother is the alpha-amylase (noted as α-Amylase). Alpha-amylase is everything beta is not. Where beta is precise in converting starches to sugars, the alpha is slap dash. Alpha-amylase hacks at any ol’ molecule string, leaving behind sugars that can be many molecule-structures long. While this may result in some sugar molecules that are easy pickings for the yeast, it’s just as likely that there will be long strings of sugars that are simply too large for the yeast to consume. The result? Less alcohol after fermentation, but more flavor, in the form of a dextrinous wort.
As a brewer can tell you, both of these conversions of starch have their advantages. As I’ve mentioned repeatedly, where a brewer focuses their attention is dependent upon what type of beer they are brewing. Different attentions will produce beers optimal for different yeasts. The point here is illustrate that brewing is a very precise craft, one that shouldn’t be approached without a fair amount of forethought.