Fermenting Beer

By Jack Horzempa

History of yeast

In the Reinheitsgebot (German beer purity law) of 1516 there were three ingredients listed in brewing beer: barley (malt), hops and water. As any brewer today knows there is one ingredient missing from that list: yeast.

Yeast as a microorganism was not known in 1516 but there is little doubt that brewers were aware that something ‘else’ was needed to produce beer.

For example, from a Middle English dictionary (Editor: Sherman M Kuhn; The University of Michigan Press):

“Berme [yeast], otherwise clepid [called] goddes good [god's good], withoute tyme of mynde hath frely be goven .to ye value only of a ferthyng .bicause it cometh of ye grete grace of God.”

The above reminds me of another quote which is mistakenly attributed to Benjamin Franklin:

“God made beer because he loves us and wants us to be happy.”

Well the brewers of yore certainly thought that God provided to them yeast so they could produce beer. One of the tricks they would use is to have a favorite wooden paddle as Michael Jackson (the beer Michael Jackson) described it:

“Brewers in the middle ages had no idea about the presence of yeast and the role it plays in beer production. These rustic brewers would often stir a new vat of wort with a "magic" wooden paddle inoculated with yeast cells from previous batches. Fermentation would kick in within a few hours.”

Science to the rescue

Many folks are familiar with Louis Pasteur since he came up with the process of pasteurization to help milk keep longer.

But prior to coming up with the pasteurization process, in 1856 he studied quality problems some manufacturers of beet root alcohol were having. What the heck is beet root alcohol you might ask (as do I)? Well, I do not know what folks were drinking in 1856 but beets are a source of sugar (e.g., sugar beets) and we all know that it is sugars (i.e., the sugars in wort) which are the food for fermentation. During his studies Louis Pasteur discovered a number of single cell microorganisms involved in the fermentation process. The good microorganisms were the yeast (which are a fungus) and the bad microorganisms were bacteria which would create undesirable flavors like sour (spoilage) flavors – for example Acetobacter aceti.

Perhaps Louis Pasteur would have said that when it comes to fermentation it comes down to the little things?