Hydrolyzed corn products in brewing

Phil was considering using corn syrup as a brewing adjunct. Corn is a cheap source of starch and from it a range of hydrolyzed products can be obtained. To avoid confusion, I consider it useful to briefly describe to use of corn derivatives in homebrewing. As an introduction, I will mention the processing of barley required prior to brewing.

A grain of barley is largely an energy source for the germinated seedling that it will nurture. The energy in a grain of barley is stored mostly as starch. Starch (polysaccharides) must be cleaved into smaller units such as maltose (a disaccharide) by enzymes in the germinated grain to make useful fuel. Enzymes from within the grain perform this function when barley is warm and moist. Artificially raising the temperature after germination speeds up enzyme activity and is called "malting". The malting process converts most of the tasteless starch into sweet maltose.

Barley is easily malted because it is rich in those enzymes that hydrolyze starch and generate maltose and some other dextrins. The enzymes from barley are sufficiently active that additional sources of starch such as corn or potatoes may be added to a mash containing barley. The barley enzymes will go work on corn starch and potato starch thereby generating extra fermentable sugars.

The use of starch derived from sources other than barley has become entrenched in brewing. The use of corn or rice in brewing tends to generate a beer with less body and flavour than its all-malt brother. Most of the commercial beer kits in Australia are made from malted barley and, to a lesser extent, wheat. Adding corn or potato starch when making up your wort will be ineffectual as active enzymes will not be available to hydrolyze starch. (The starch will harmlessly silt out in your fermenter).

To replicate those beers which may have incorporated corn, or simply to be economical, a variety of hydrolysed starches are available. These products are prepared via the controlled action of acids and/or enzymes on corn (or wheat or potato) starch. If partial hydrolysis has taken place, the starch will have been converted into an assortment of dextrins (oligosaccharides). Complete hydrolysis of the starch will yield dextrose (the monomer of corn starch).

Those dextrins derived from corn are called maltodextrin or corn syrup solids. These oligosaccharides are, unlike starch, soluble in water. However, they are mostly inaccessible to yeast as a food source; thus maltodextrin adds body to a beer (suggestively described as "mouth feel") and little else. Although yeast cannot access maltodextrin as a food source, you can! In this way maltodextrin can add a little to your body too.

Dextrose (also called corn syrup or glucose) is also soluble in water but is readily and completely digested by yeast. This monosaccharide increases the alcohol concentration of the brew as it is consumed. As alcohol is less dense than water, simple sugar adjuncts such as dextrose also effect a thinning of the beer. Likely, this is why dextrose and maltodextrin are often used in conjunction with each other.