Our friend yeast

Unproved bread dough

Proved bread dough

It doesn’t matter how many times I make bread, I always find the rising, the leavening, of dough enormously pleasing. The quiet industry of yeast is nothing short of a wonder, and our relationship with it remarkable.

Yeast is a microscopic type of fungus. Of course, “yeast” in the baking and brewing senses refers to a variety of different species of yeast. Predominantly, however, bakers’ yeast is a strain of Saccharomyces cerevisiae. The main yeast used in brewing is also a strain of Saccharomyces cerevisiae. It’s also a key player in winemaking.

Some etymology
Myco is the Greek for fungus (with mycology the discipline of studying fungus). Saccharo, like saccharine, is also from the Greek, for sugar. So Saccharomyces means sugar-fungus.

Cerevisiae is generally translated as meaning “of beer”, but to go a little deeper, it’s presumably related to Ceres, the Roman goddess of grain, agriculture, and fertility, and the origin of our word “cereal”. (Ceres is also the name of a yucky strong Danish lager much loved by undiscerning Italians, but we won’t go into that.)

Cerevisia / cervisia means “beer” in Latin, and is the origin of the Spanish cerveza and even the obscure Italian word cervogia. Indeed, struggling through an Italian etymological dictionary, the vis is the Latin for “force” or “strength”, so the Latin name for beer seems to literally mean “the drink containing the strength of cereal”.

This is one of those many occasions when I wished I’d studied Latin. I went to a flippin’ Catholic school for crying out loud, but we didn’t do Latin!

Anyway, for most of humanity’s long history of bread-making and brewing, we were oblivious not just to the specific strains of yeast, but even to the whole concept of microorganisms. And yet there they were, helping us access the nutritional qualities of grain through the millennia. Yeast was first observed in 1680, but not recognised as a living thing. Louis Pasteur identified yeast as the cause of alcoholic fermentation in 1857 and the cause of dough inflating a few years later.

Even today, there’s plenty of disagreement about certain aspects of the nature of yeast: according to various figures, in a single gram of yeast, for baking or brewing, there are between 8 and 20 billion cells.

Oh, and after all that Latin and Greek, the word yeast itself is from the Old English gist/gyst, with very similar words in other northern European languages and, it seems, a Sanskrit root – yásati, meaning “(to) boil” or “to bubble”

Fungus fun for all the family
So thanks yeast. Or yeasts, as it’s not just S. cerevisiae. Other Saccharomyces are used in the production of food and drink, such as S. pastorianus (the hybrid strain used for bottom-fermenting lagers and pilsners; formerly known as S. carlsbergensis), S. bayanus and S. uvarum.

Then there’s the whole Brettanomyces genus. This name means “British yeast” and was so-named during investigations into English ales at the Danish Carlsberg brewery in the early 20th century. B. bruxellensis is an essential element in the production of Belgian Lambics and related sour beers.

Then there are other genera like Kazachstania, with K. exigua, found in sourdough cultures and olive brine. Heck, even the Candida genus comes into play. Yes, C. humilis, a yeast from the genus responsible for a lot of fungal infection, and even wine spoilage, is considered the “dominant species” for the production of some sourdoughs.

I like dogs, but with their invaluable services in the production of staple food and drink, to leavening bread doughs and fermenting alcohols, perhaps these yeasts have a better claim to being man’s* best friend(s).

* Sorry, inherently sexist language. Can’t really sidestep this by putting mankind’s or humanity’s either.

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