The Process of Making Beer Wort
Making beer wort (unfermented beer) involves several steps. The first of these is mashing. The primary goal of mashing is to finish the breakdown of proteins and starches that the maltster began when he produced the malt.
In days past, when malts were less modified, the mashing process was accomplished by using several steps that utilized various groups of enzymes to degrade different parts of the proteins during a series of rests within a specified range of temperatures.
Beer Wort – The Acid Rest
Before the chemistry behind the interaction of malts and water was well understood, brewers in certain areas had difficulty getting their mash pH to reach the acceptable range when using only pale malts. The darker grains, and especially the highly kilned malts, acidify the mash, and brewers using these malts do not have the problems with mash pH that those in Pilsen had.
The reaction of the malt’s phytase enzyme breaks down the phytic in pale lager malts into calcium, magnesium phosphates, and phytic acid. The mash pH is lowered by removing the ion buffers and producing a weak acid, phytic acid. Today, using the proper mineral additions, proper mash pH can be achieved without an acid rest.
The only time one might want to employ this mash is when using a large percentage of brewing adjuncts with high levels of hemicellulose and gums in their cell walls.
The enzyme beta-glucanase works in this temperature range to break down these substances to help prevent stuck mashes or other problems when a large percentage of rye is used in the grist.
The Protein Rest
The next step in the mashing regime is protein rest. It is employed for under-modified malts, which may still be purchased from German maltsters.
These moderately-modified malts benefit from a protein rest in the range of 113°-131°F (45°-55°C) to break down any remaining large proteins into smaller proteins and amino acids. Some brewers feel they get a fuller and maltier flavor profile by using a protein rest on less modified malts.
Malted barley has many amino acid chains which were in place for the germinating plant. The yeast now uses them for their growth. The two main enzymes responsible for protein degradation are peptidase and protease. The peptidase provides the wort with the amino acid nutrients the yeast uses. Protease breaks down the larger proteins, which help enhance head retention and reduce haze. For most of us that use well-modified malts, the work of the two proteolytic enzymes has already been completed during malt production. You don’t want to do a protein rest with well-modified malts because of the breakdown of the proteins which produce body and head retention. The resulting beer would be thin and watery.
However, when using a grist with >25% of unmalted grains like flaked wheat, rye, oatmeal, or barley, employing this rest will break up the beta-glucans, which, if left intact, may cause a gummy mess and get stuck mash. The enzymes which accomplish this are the beta-glucanases and beta-cytases. Fortunately for the homebrewer, these enzymes have an optimum temperature that is below that used by the proteolytic enzymes, allowing us to rest in the 98°-113°F (37°-45°C) range without affecting those proteins we need for body and head retention.
When using less than 25% unmalted grains, a mashout will aid in solubilizing the gums before running off into the wort.
The Saccharification Rest
For most of the homebrewers in the world, the only rest we use is the saccharification rest which gelatinizes and then converts the starches into dextrins and fermentable sugar.
The gelatinization (or the “melting” of the bonds in a starch’s crystalline structure) temperature for starches in our mash is in the 130-150° (54°-66°C) range for barley malt. When using raw grains such as corn grits, the gelatinization temperatures are higher, and thus, they must be boiled in a separate cereal mash before being added to the mash. The alpha and beta amylases work by hydrolyzing the straight-chain bonds between the glucose molecules in the starch chain.
One single starch chain is called amylose (about 25% of the barley malt starch is amylose), and a branched chain (made up of amylose chains) is called amylopectin (which makes up the other 75% of the starch in barley malt). Both enzymes, beta-amylase and alpha-amylase, attack the starch but do so in different ways.
Alpha-amylase randomly chops up starch molecules into chunks that beta-amylase can work on. Until these molecules are chopped up, they are unfermentable and called dextrins. What alpha-amylase does is called liquefication? It physically liquefies the starches, making them ready for further enzymatic activity. Mash schedules that target the alpha-amylase enzymatic action (optimum range of 149° to 158°F/65°-70°C) yield a wort with a high percentage of unfermentable sugars or dextrins. The beer produced is very rich, with a thicker body and mouthfeel.
Beta-amylase breaks down starch and dextrins into glucose (one molecule), maltose (two molecules), and maltotriose (three molecules). After beta-amylase works, the starch has been broken down into fermentable sugar. Mash schedules that target the beta-amylase enzymatic action (optimum at 140°-149°F/60°-65°C) yield a wort that is highly fermentable. The beer produced will be drier tasting and contain more alcohol.
Customize Fermentability of Your Beer by Adjusting Mash Temperature
What this knowledge means to homebrewers is that they can customize the fermentability and body of their beers by adjusting the mash temperature and, thus the enzymatic activity.
It is important to understand that although mash enzymes have an optimum temperature, they will work over a wide range, and most of the time, the activity of enzymes overlaps within that range.
Both alpha-amylase and beta-amylase will work well together within the range of 145° to 158°F (63°-70°C). So, in general, if you want a thinner, drier, more alcoholic beer, you can mash in the lower portion of this range, and if you want a richer, more dextrinous beer with more mouthfeel and body, you should mash in the upper portion of this range. A good compromise is made by mashing in the middle, around 152°F (67°C).
Adjusting Mash Thickness
Another variable homebrewer can affect is mash thickness. A thick mash (which has a lower water/grain ratio) will keep the enzymes in contact with the starches and allow them to work better and quicker.
A thick mash, <1.25 qts. of water/pound of malt, is better at breaking down proteins and results in faster starch conversion. But, the resulting sugars will be less fermentable, and the beer will taste sweeter and maltier. It should be noted that a thick mash is easier on the enzymes because heat transfers less in grain than in water. The result is that the enzymes are protected from the denaturing effects of high temperatures in a thick mash. Using a thicker mash for the homebrewer will allow the beta and alpha-analyze enzymes to work in concert when using a single infusion mash at higher temperatures.
A thin mash, >2.0 qts. of water/pound of malt, dilutes the relative concentration of enzymes in the mash. Thin mashes are much easier to move around, have better heat transfer, and produce a better yield since the starches are more easily dissolved. One problem with a thin mash is the stability of the enzymes. They are more prone to the denaturing effects of higher temperatures. The resulting beer will be less fermentable if the beta-analyze enzyme denatures too quickly. A thin mash will slow down starch conversion but ultimately produces a more fermentable, thinner, and drier beer because the enzymes are not inhibited by the increased concentration of sugars in the wort.