Enzymatic Activity in Mash
The last post explained a couple of advanced mashing concepts, one of which focused on using maize (corn) as an adjunct. When looking to maximize the efficiency of ingredients it is paramount to understand the structure of the starch source.
If you are relying on naturally occurring enzymes, it is best advised to use a grist composition of 80% or better malt to provide sufficient enzymes. Key temperature rests must be met, pH range buffered, and proper hydration achieved for enzymatic activity to “digest” and solubilize saccharides into the mash liquor. The resting time needed will vary based on the specifics, and even small deviations from the optimal parameters mentioned can have large impacts on enzymatic activity in the mash.
Mashing is the process that separates brewing (beer) from other forms of alcohol production. The reduction of carbohydrates into various saccharides requires more time and energy than a direct monosaccharide fermentation, however it allows for many raw ingredient choices, and a large potential for flavor divergence. Full control of the saccharide reduction and ultimate solubilization is essential for economic efficiency and for metabolic action by yeast.
Supplemental enzyme additions can be used for large quantities of adjuncts, but can also be used in standard brewing applications. Beyond a numerical increase in the content of actual enzymes present in the mash, they can offer a wider temperature stability range, increased hydrolysis, and improved liquefaction. Blends of enzymes with unique advantages exist, such as cleaving bonds that normal barley enzymes cannot. This can allow for a more complete degradation of cell walls during the conversion activity, and thus better extract potential. With ideal targeting, the mash times can potentially be shortened opening time for more brews per year.
Quality of collected wort is a primary concern for all brewers, but especially for those new to supplemental enzymes. Yeast (S. cerevisiae, S. pastorianus) would prefer to metabolize glucose and fructose, and does not particularly like to make use of galactose. The first two are common in brewing, and the third is usually only seen with the addition of milk sugar (Lactose=Glucose+Galactose).
Typical wort is primarily composed of Maltose (50-60%), followed by Maltotriose (15-20%) and then Glucose (10-15%). All of these are glucose based, making wort the ideal substrate for brewing yeast to metabolize. The yeast will take a path of least resistance, first processing any available glucose, then maltose (glucose+glucose), and finally working on maltotriose (glucose+glucose+glucose). Yeast preferences glucose because it does not require energy for uptake (passive transport) whereas the uptake of maltose and maltotriose requires ATP to ADP conversion (active transport).
Ale yeast (S. cerevisiae) has been shown to have difficulty metabolizing maltotriose completely and its uptake into the cell is much slower than lager yeast (S. pastorianus). This means ales can be prone to residual levels of maltotriose (which may or may not be desirable). It has been shown that yeast propagated on glucose can have increased difficulty in transitioning to subsequent fermentation of maltotriose.
Maltase is the enzyme responsible for the breakdown of maltose and maltotriose into glucose. It naturally occurs in the human body and is thought to originate in the intestinal lining. It is also naturally present in many yeast and bacteria. The maltase will act upon the maltose inside the yeast cell, splitting it into two usable glucose molecules. Certain yeast strains, such as S. cerevisiae var. Diastaticus can have a-glucosidase expressive genes that are regulated by the amount of glucose present.
Tailoring the wort sugar composition to the specific fermentation organisms can help increase real attenuation as well as influence flavor. A great example is mashing wheat beers with a maltase rest to increase the available glucose content. Isoamyl and ethyl acetate increase with the amount of glucose available, and will correspond with a reduction in acetaldehyde. This will add a nice balance of fruity and banana like character to our 4-vinyl guaiacol/clove bomb we suggested in the last posting.