Summer 2011

“Beer isn’t made by the brewer; it’s made by the yeast!!”

I heard this from a brewer just the other day. Beer needs much more than a person to be made, of course, and the key ingredient is yeast. Yeast creates alcohol and carbonation, as well as fruity qualities through esters.

Since yeast is incredibly important in the production of beer, it behooves the brewer to create an environment conducive to properly functioning yeast. For example, in the very beginning of the brewing process, ground barley is added to hot water to make a mash. Those grains contain starches that can be converted into sugars. These, in turn, are like nutrients for the yeast to gobble up. The liquid component is eventually separated from the mash. If it’s too hazy, the yeast’s function will be inhibited; naturally, brewers use this good clean stuff called wort.

The wort is boiled for about 90 minutes for a number of reasons, though mainly to kill bacteria. During fermentation, bacteria other than yeast can have a detrimental effect, so best to kill them, right? Then, the wort is cooled and transferred to a fermentation tank where a temperature appropriate for the yeast to do its work can be maintained. This is basically how brewers create an environment that is stress-free and rich in nutrients for yeast. Let the yeast do its work and hope for some great beer!

Years ago, breweries were always struggling with lactobacillus. The difference between fermentation and a spoiled batch came down to, say, a brewer calling what could still be drunk, “fermentation,” and what couldn’t, “spoiled.” Talk about walking a fine line!

There was one individual, however, who lowered this risk for brewery infection. Emil Christrian Hansen was a Danish mycologist who, during his heyday, was working in the Carlsberg beer laboratory and discovered the cause of brewery infections. Basing his work on the research of Louis Pasteur (of pasteurization fame), he established the “yeast pure culture method.” With a pure culture, you may still take yeast from some kind of food sample to grow, and there are various strains. Those strains grow into colonies. The trick is in choosing one and growing it so that you have a pure strain. Hansen separated desirable yeast from bacteria and other wild yeast strains, cultivated it, and made breweries a place of science, not luck.

Thanks to Hansen, we now have a rich variety of good yeasts and brewers can choose from those varieties to make a certain style of beer that they like. Brewers who make delicious beer understand the qualities that a given yeast imparts to a beer. Brewers are in fact yeast farmers, perhaps more than beer makers!

This article was published in Japan Beer Times # () and is among the limited content available online. Order your copy through our online shop or download the digital version from the iTunes store to access the full contents of this issue.