Dear Reader, usually the deal here on Aard is that I tell you what to think and you reply, zombielike, “Yes… Master… Kill… Kill…”. But today, let’s turn the tables. I’m going to ask a question about a simple scientific-culinary matter that has baffled me for decades. And I hope someone out there knows enough about yeast to enlighten me.
- When starved of oxygen, yeast turns sugar into alcohol.
- When germinated, barley grains, by means of the enzyme amylase, turn some of their constituent starch into sugar. This process is called malting.
- In order to make beer, you must malt the barley. This suggests that yeast cannot make alcohol out of starch.
- But Swedish vodka is made from potatoes, which are very high in starch but cannot be malted. This suggests that yeast can make alcohol out of starch.
So here’s my question: if yeast can make alcohol directly out of starch, why bother malting the barley before making beer? Couldn’t you just mix barley flour with water and yeast and put a lid on the slop?
Update same evening: Dale P and other Dear Readers solved the conundrum fÃ¶r me. Yeast cannot in fact ferment starch. To ferment potato mash, you add enzyme-containing barley malt to it!