Alcohol, specifically ethanol, is the stuff we drink. Beer, wine, whiskey, vodka, tequila, schnapps, it doesn’t matter. The alcohol itself is all the same. But where does ethanol come from? Yeast. Yeast makes alcohol. How they do it is pretty amazing.
Yeast is a microorganism, a living thing. Like all fungi, they have some plant characteristics and some animal characteristics. Yeast makes alcohol through a biological process. Sugar, dissolved in water, is ingested by the yeast organism. The sugar is metabolized, generating energy for the organism’s life processes such as reproduction. The waste product it discards consists of alcohols (primarily ethanol) and carbon dioxide.
This process is called fermentation.
Since yeast eats sugar, it is easier to make alcohol from sugar sources (fruit, honey, sugar cane juice) than from starch (grain, potato). Saccharification is the process of converting starch into sugar, thereby making it something yeast can eat. It is a prerequisite for making beer and whiskey.
Grains are seeds. To grow, new sprouts need sugar, just like yeast do. So at the beginning of the germination process, the new sprout produces diastatic enzymes that convert the starch surrounding it into sugar. The process of sprouting grain to capture those enzymes is called malting. Any grain can be malted but barley is particularly good. The enzymes produced are so effective that a relatively small amount of malt (about 10%) will convert a mash of unmalted grains.
In Scotland, the law requires that only barley malt is used in the production of whiskey. In the United States, enzymes derived from other sources may be used and sometimes are, but most whiskey-makers use malt. Some use both.
All of the alcohol we drink is still made the old-fashioned way, by feeding sugar to yeast.
Enzymes are proteins that promote chemical reactions. All chemical reactions within cells are controlled by enzymes, so enzymes are also involved in the biological process by which yeast makes alcohol. You might think that modern science could just synthesize all of these different chemicals and make alcohol in some kind of machine. Maybe it can, but all of the alcohol we drink is still made the old-fashioned way, by feeding sugar to yeast.
All of these processes take place in water so before anything else can happen the starches have to be dissolved. First, they are ground to the consistency of corn meal, then water is added. Most starches have to be cooked to fully dissolve. This is especially true of corn, the main ingredient in bourbon whiskey.
Some solids, mostly cellulose, remain undissolved. Most brewers and some distillers discard the solids. Bourbon makers typically do not and they continue through the distillation process.
Regardless, in the end, after the yeast and sugar are mixed and mashed, we have alcohol and it’s delicious!
This article originally appeared on the Chuck Cowdry Blog.
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