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Complex Numbers #960866 added June 16, 2019 at 1:16am
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It's the Yeast We Can Do
https://www.atlasobscura.com/articles/cross-continental-origins-of-beer-yeast
Beer: Bringing the World Together.
The researchers found that Saccharomyces cerevisiae, the species of yeast that has been used to brew certain beers for thousands of years, is in fact a mixture of yeast strains found in both European grape wines and Asian rice wines. And so, they write, there would be no ales or lagers if not for the cultural exchange of fermentation technologies between Asia and Europe, possibly on the Silk Road.
There exists a sake brewery  here in my hometown now. I've been all over the country, and this is the first one I've ever seen. Naturally, I paid it a visit.
Sake is known as "rice wine" here in the English-speaking part of the world, but something about that never sat right with me. It's a fermented beverage, yes, like beer, wine, cider and mead. But the definition of beer is basically a fermented beverage made from grain, while wine is a fermented beverage made from fruit. Thus, cider is actually a wine... and sake could be considered a beer. Mead, being made from honey, which in turn is processed by sting bugs from flower pollen, is in a class by itself.
My trip to the sake brewery shed a bit of light on this terminology glitch. Wine tends to have a higher ABV (alcohol by volume, which measures the relative amount of ethanol in the elixir) than beer. The ABV of sake also tends to be on the high side, while the ABV of cider tends to be closer to that of beer. It appears that this is the source of the terminological confusion.
So, what controls ABV? Well, mostly, it's the yeast. As I understand the process, ethanol is produced by yeast when it processes sugar. In wine, that sugar is already in the fruit; for beer, a preliminary process converts the starch in the grain into sugar. Thus, anything with sugar or starch in it can conceivably become the source for delicious nectar - but some will be better than others. Barley is the go-to grain for beer; obviously, most wine is made with grapes. Some beers have other grains added. Some wines have other fruits added (I once had a pineapple wine on Maui, and it was delicious).
As the yeast performs its magic, eventually enough alcohol is produced that the yeast actually finds it toxic, and fermentation stops. It is also possible to halt fermentation at a desired alcohol level; this is done, for example, when local laws prohibit anything above a certain ABV. It is also possible to do things later to increase the concentration of the alcohol; taken to an extreme, you get distilled beverages such as whiskey or vodka.
An early stage of bourbon production, for example, is called "beer." This is not a particularly drinkable beer, and has not had hops introduced, but it's the fermentation product that will later be distilled into amber deliciousness.
So, basically, yeast eat sugar and pee alcohol, and when the pee builds up enough, the yeast starts to die off.
For the vast majority of the history of fermented beverages, people didn't know what yeast really was. It took microscopes to figure that out, and those weren't invented until the 17th century. By comparison, fermented beverages have been around for at least 10,000 years.
So... SCIENCE!
Thus, different strains of yeast can be isolated now, and some of them have a higher tolerance for ethanol than others.
The researchers sequenced the genomes of these strains—two ale, one lager, and one that contained both beer and baking strains—and compared them to a panel of every publicly available yeast genome from around the world, plus those from additional strains in their lab.
You're doing the holy work, scientists. Keep it up.
I should add, because the linked article doesn't really go into it, that there are basically two varieties of beer: ale and lager. The difference? The kind of yeast used. Each has its own preferred temperature. Ale lagers, as I understand it, are more tolerant of a higher alcohol content; therefore, ales tend to have a higher ABV than lagers. (Ale and lager each have many subcategories, of course, but those are the two parents of the family tree, as it were.)
So now I'm wondering what happens if you use a wine yeast for beer or vice versa. Can't be arsed to look it up right now, but I'm sure someone's looked into it. After all, it's a topic worthy of much study and contemplation, preferably after tipping back a few. |
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