CRAFT by Under My Host® No. 3: Preservation & Hibernation - Page 148

Yeast: A Story of Alcohol, Flavor, and a Triceratops Riding a Lawnmower By Colin Joliat Have you ever wondered why a German Hefeweizen tastes like fruit when the only ingredients are barley, hops, yeast, and water? I love fermented beverages as much as the next guy, but from where do those flavors come? The answer is yeast, and it’s far from boring science. There’s even one man trying to harvest yeast from dinosaur bones to make the world’s first T-Rex beer! As the crude but accurate saying goes, yeast eats sugar, pisses alcohol, and farts CO2. To yeast, ethanol is just a byproduct of fermentation. It means as much to the microbe as your fifteenth trip to the bar’s bathroom does to you. To we thirsty boozehounds, on the other hand, yeast’s byproduct means the world. There are plenty of waste products that can be repurposed, like manure for fertilizer and spent grains as feed, but few are as wonderful as alcohol. While fermentation may be a mystery to most, the process is actually quite simple. To extrapolate on the oh-so-quotable explanation above, fermentation is the process in which yeast consumes simple sugars for energy and creates carbon dioxide and ethyl alcohol as waste products. During the mashing process, milled grains are combined with water and then boiled. The enzymes in the malt convert the starches into sugar, which is what the yeast will feed on to create alcohol. This happens during the fermentation stage of © Hundred-to-One LLC 2014. All rights reserved. brewing, which is, as they say, where the magic happens. The yeast replicate rapidly and consume the sugar. As more sugar is converted, more alcohol is created and CO2 is released. Aside: It’s thought that yeast evolved to produce alcohol as a waste product because it helped kill off other sugar-consuming microbes that couldn’t survive in alcohol. It was basically the first act of biological warfare, and we’re reaping the benefits. Does that make us war profiteers? You might have noticed some foamy action last time you peeked inside a fermenter during a brewery tour. That’s because of what the cool kids call top-fermenting yeast. Their ideal fermentation temperatures are between 50°F and 77°F, which creates more esters that we so often associate with ales. Bottom-fermenting yeast doesn’t have the same Bubblicious effect. It needs colder temperatures than top-fermenting yeasts, in the neighborhood of 45°F to 60°F, which doesn’t result in much yeast flavor in the beer. Instead, it creates crisper, cleaner beers, which is why it’s typically called “lager yeast.” (not why it’s called “lager yeast.”, lager means ‘to store’ and they take ‘longer’ to ferment). Carbonation is key to any great beer, and it can be attained a few different ways during and after fermentation. First, the