So given the same brewing parameters, WLP001 would dry the beer out further than 007?
Let's start with a very basic overview of organic chemistry. All sugars belong to a class of substances known as carbohydrates. Carbohydrates are a combination of carbon and water (hydrated carbon). The simple sugars found in wort are multiples of CH2
O. Simple sugars are known as monosaccharides. The simple sugars found in wort are primarily glucose and to a lesser extent fructose and galactose (an "ose" is a sugar). These sugars are classified as hexoses because they contain six carbon atoms. The chemical formula for all three sugars is C6
. They only differ in form.
The sugars found in wort that are more complex than the hexoses are known as disaccharides and trisaccharides. A disaccharide is a sugar that contains two monosaccharide molecules bound by what is known as a glycosidic bond. A trisaccharide is a sugar that contains three monosaccharide molecules bound by two glycosidic bonds.
Glycosidic bonds result in the loss of one H2
O molecule per bond. For example, maltose is a disaccharide that consists of two glucose molecules bound via a glycosidic bond. While the chemical formula for glucose is C6
, the chemical formula for maltose is not C12
(2 x C6
). It is C12
. That's because we loose an H2
O molecule when we combine two glucose molecules to form maltose.
In order for a yeast cell to use a disaccharide or a trisaccharide, these sugars must undergo an important process known as hydrolysis. That word should look familiar to anyone who has dealt with a primary fermentation bogeyman; namely, autolysis. Hydrolysis is the combination of “hydro” (water) and “lysis” (break apart). Hence, hydrolysis is the breaking apart of sugar via the addition of water. We need to add one water molecule per glycosidic bond in order to release the simple sugar molecules.
O -> C6
To take a step backwards, mashing is the simple name for a biochemical process known as hydrolysis of starch. Like hydrolysis of starch, hydrolysis of sugar requires enzymes. Enzymes serve as hydrolysis catalysts. Catalysts are substances that speed up chemical reactions. Yeast cells produce the enzymes necessary to hydrolyze disaccharides and trisaccharides into monosaccharides.
Now, here’s where yeast genetics come into play. Enzymes are proteins. Proteins are made up of amino acids. Genes are responsible for encoding amino acids into enzymes. Different yeast strains encode the enzymes that catalyze the hydrolysis of complex sugars into simple sugars to different degrees. Some yeast stains do not encode the enzymes necessary to hydrolyze certain sugars. For example, the Windsor yeast strain cannot break down the trisaccharide maltotriose (C18
), which is composed of three glucose molecules bound by two glycosidic bonds. That’s why it leaves a higher than normal terminal gravity.
By wort composition, I do not mean the composition of the grist that we used to make a batch of wort. I mean the proportions of monosaccharides, disaccharides, trisaccharides, and dextrins in the wort.
According to Fix (Principles of Brewing Science), mashes produced at 60C (140F) and 70C (158F) have the following compositions:
Monosaccharide – 10%
Disaccharide – 61%
Trisaccharide – 9%
Dextrin – 20%
Monosaccharide – 8%
Disaccharide – 41%
Trisaccharide – 16%
Dextrin – 35%
As one can clearly see, not only does the percentage of dextrins in wort rise with respect to mashing temperature, the percentage of trisaccharides rises as well. To a great extent, the ability to ferment the trisaccharide maltotriose determines the relative attenuation of any given yeast strain for a specific wort composition. Bry 96 (a.k.a. “Chico,” 1056, WLP001, US-05, or simply Ballantine) is very good at breaking maltotriose down into glucose. Pretty much all that is left after it has completed fermentation is dextrin and a small amount of melibiose.