Chemistry of Beer – Unit 5 – Mashing and Lautering
>>So far in our journey in the brewing process,
we’ve malted our barley, and we have kilned the malt. The next step is going to be mashing
and lautering. The mashing process we’re going to let the enzymes and the malt break the
starch and the sugar, most often maltose. There’s two forms of mashing: infusion and
decoction. In infusion we mix the malt with the water, and we heat it up together. It’s
a newer process that really became available when we had very accurate thermometers. In
decoction what we do is take a portion of the mash and boil it, take that boiled content
and put it back in with the rest of the mash to raise the temperature. This is an ancient
process that was used whenever there were not accurate thermometers. Both of these are
used to get the mash up to a certain temperature, but not boiling. What we want is our enzymes
to be active. There are specific temperatures where these enzymes will be active. Once we
have exceeded this temperature, the enzyme is denatured and no longer active. When we start the mashing process, we start
with malt. The malt is still in granular form, in its grain, so we first need to break that
open to increase the surface tension. So we’re going to mill the grain to get a grist. The
grist is then mixed with water, and the water is then heated up to a certain temperature.
There are several enzymatic rests. The enzymatic rests are temperatures where we get the most
enzymatic activity. There is the beta-glucanase rest, the protease rest, and the amylose rest:
either the beta-amylose rest or the alpha-amylose rest. The beta-glucanase rest is actually
a enzyme that breaks down beta linkages in cellulose. This enables the starch to come
out of the cell walls. You have to be careful with this rest because if you break down the
cellulose too much, it’ll actually interfere with the filtering process and the lautering
step. The proteinase rest degrades proteins, giving free amino acids and other smaller
protein molecules. We have to be careful here because if too much free amino acid in the
wort will actually cause off flavors. We also want to have smaller proteins for a developed
head, but if we break down the proteins too much, it’ll also cause clouding. The amylose rest, both the beta- and alpha-amylose
rest are the most important. It’s the amylose enzymes that are going to convert the starch
into sugar. The beta-amylose rest is for the beta-amylose enzyme. This enzyme will break
down amylose and amylopectin by starting at a non-reducing end and then breaking it glucose
by glucose. The alpha-amylose rest more or less takes the larger starch and snips it
into smaller pieces. Depending on where we set the temperature, either at a optimal beta-amylose
rest or an alpha-amylose rest, will change the overall flavor and texture of the beer.
If we have a lower temperature, we’re going to favor a beta-amylose rest. This is going
to give us a crisper, less malty beer. If we have a slightly higher temperature at the
alpha-amylose, we’re going to leave smaller dextrin molecules together that give us a
malty flavor and a more full-bodied beer. So once we’ve completed the enzymatic rests,
we then want to get to the lautering process. Before we get that, what we do is a mash out.
Remember we’ve set our temperatures to optimize the enzymatic activity, but at these lower
temperatures the wort is still very thick, and what we want to do is make it less viscous.
So we raise the temperature, or mash out. So we’ll raise the temperature up and prepare
for the lautering step. Now lautering is just the process where we’re
going to separate our liquid wort from our residual grain. Usually this is done by sparging.
We sparge by putting a little extra water into the mixture. This extracts out more of
the fermentable sugars, but we have to be careful. There are tannins in the grain husks.
If we extract too many tannins, we can get a very bitter or astringic beer. At the end
of lautering, what you have is you have your spent grain and you have your liquid wort.
It’s our liquid wort that we’re going to take to the next stage of the brewing process:
boiling and hopping. The main step in the mashing and lautering phase is to convert
starch into simple sugars that can be digested by the yeast and turned into ethanol.