Island Brewing / The Keg & I

 By Jim Brady

Brewing 101:  The Mash


We hear the term “craft” beer a lot.  What is so “crafty” about it?  Let’s talk about that.  Let’s start with the “mash,” the first step in the brewing process.

Brewers are geeky folks.  They must manipulate several sciences.  Not only is an understanding of chemistry and microbiology required, but mechanical and engineering skills are necessary to design, maintain, troubleshoot and operate the brewery equipment.  In addition to that, a brewer needs creative imagination to add artisan twists to classic beer styles or create a specialty.  A brewer is a master of multiple crafts.  His beer is an artistic rendering of those crafts.

For you geeks out there, let’s talk about these sciences in simple terms.  Beer must be made of at least 40% barley.  Though other grains like oats, rye, and wheat may be added, they do not contain the necessary enzymes that barley has to convert their grain starches into the sugars that yeast need to metabolize.  Once the grains are crushed, water is added to form a porridge called a “mash.”  The temperature of the mash is raised and held at different “rests” throughout the mashing process.  Different enzymes become active during these rests to perform a variety of reactions essential to conversion.  We need not get too technical here since it’s the final rest that is the most important.

The last rest(s) occurs between 131°F and 162°F.  Within this range, two important enzymes become active to break down the grain starch molecules into sugar.  These enzymes are called alpha and beta amylase.  Starch is a long chain of sugar molecules stuck together.  Alpha amylase tends to chop the chains in half while beta nibbles at the ends.  Brewers can manipulate the mash temperature to balance or favor the enzymes.  Alpha likes the higher temps and creates dextrines (bigger sugar molecules) while beta likes the lower temps and creates smaller molecules.

Dextrines are difficult for yeast to metabolize and remain in the finished beer to lend body or “chewiness” in the mouthfeel.  Alternately, the smaller molecules created by beta amylase are easily consumed by yeast whose byproducts are carbon dioxide and alcohol.  What this manipulation of enzymes translates into is a beer that either has more body or one that has a higher alcohol potential.

Once starch conversion is finished, the sweet “wort” is strained from the grain in a process called “lautering.”  It is boiled in a kettle for sixty to ninety minutes where proteins in the wort coagulate into flakes called “hot break.”  Hops are added at different times to extract their bittering, flavor and aroma qualities (alpha acids).  These acids are not readily soluble and must be boiled to create a reaction called isomerization to release them into the wort for balance.  The wort is then quickly cooled to fermentation temperature and yeast is added.

The boil and fermentation are other areas where the character of the beer can be manipulated but we can talk about those next time.  For now, stay geeky and enjoy!

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