Yeast, as Understood in 1736


I’m really glad I was able to get a second opinion on one little detail that has become of great importance to my ongoing novel project. That is: how well did brewers understand the function of yeast in brewing back in 1736? It might sound strange, but that detail is incredibly important in terms of a lot of things going on in the book!


During my visit to Korea, I got a chance to read a fair bit of Jamil Zainasheff and Chris White’s book Yeast: The Practical Guide to Beer Fermentation. I wasn’t particularly blown away by the book: in the first couple of hundred pages, where was very little that was new to me outside of the history of yeast study… though I enjoyed the history enough for parts of it to stick in my memory, and I had a feeling most of the stuff toward the end (about how to build a yeast lab) would have been new to me. Alas, I didn’t get that far before I had to return it to my friend… but I felt that I’d gotten some useful information for my novel anyway, about the poor understanding of the role of yeast in fermentation in the era in which my book is set.

Perhaps Zainasheff and White’s account of the history is simply too compressed for the detail I needed–and understandably so, since it’s not a history book nor is it aimed at a serious historical education on the subject. A lot of reviews suggested this material, earlier in the book, is of little or no use to them, which doesn’t surprise me: brewers and homebrewers especially seem to tend to want practical, useable information above all else. Arcane details of history are exciting to the degree that they are bizarre or funny. (Such as the practice of urinating in beer, which, yes, historically people did: I can’t remember the name of the practice, but it has been done, for what seemed like a good reason at the time. Yikes!)

I can imagine earlier periods where brewers didn’t even get at all what yeast was, or what it might be doing in a batch of wort, after all… And to be fair, they do mention Anton van Leeuwenhok (who incidentally was an alchemist) first viewing yeast under a microscope in 1680–and seeing “globular structures” but not thinking they might be alive.

Still, if I remember right, Zainasheff & White suggest that the function of yeast was so poorly understood that it was assumed the yeast found at the bottom of a batch of fermented beer was a byproduct, rather than an active agent, until Pasteur proved the function of yeast in fermentation in 1857. (Indeed, in Yeast I remember it being claimed that “spontaneous generation,” was deemed  responsible for fermentation, and that yeast was seen as merely a byproduct of fermentation, until Pasteur’s paper was published.)

Not my copy. Mine lacks a dust-jacket.

The problem is that history doesn’t really uphold that–Georgian brewers may not have had the theory, but they certainly had loads of practice that demonstrate a great deal of awareness of the role of yeast in fermentation. This is very obvious, implicitly, from brewhouse accounting and paperwork of the period, as can be discovered reading Peter Mathias’ The Brewing Industry in England, 1700-1830. Mathias talks about how, even by the mid-1700s, brewers may not have understood the science of fermentation, but they clearly understood that yeast played a role in it–well enough, in fact, to regard yeast as a commodity.

(They even had Yeast ledgers, in which they recorded how much surplus yeast they had harvested, pressed, and dried to sell off to distillers and bakers, and of course when they experienced spoilage, brewers had to procure new batches of yeast from other brewers… which suggests they really did know that yeast was crucial to fermentation, even if they didn’t exactly know how it worked, or what it did.)

 It just goes to show you two things I already knew, but which I seem constantly to relearn in life:

  1. Popular histories will often tend to simplify things in ways that approach distortion or misinformation: Fact X wasn’t theoretically proven until Year Z becomes Fact X wasn’t known until Year Z, because the historical details are usually less important to most readers of popular accounts. One can be dissatisfied with this, but it’s probably unfair to fault the popular account too harshly, because, well, see #2.
  2. You must always, always look at as many texts as possible when researching history on a fine-grained level, even when it’s hard to find more than one source–as it has been for me, given where I live and all that, and given the degree of specificity of my needs. (In my case, trying to figure out how well-understood the function of yeast was in brewing in 1736, which is pretty damned specific.) The finer the grain, the more texts are needed for serviceable understanding, though in my case, I’ll have to make do with the Mathias and the Zainasheff/White.

Incidentally, the Mathias is a goldmine of historical information, most of it being of absolutely no use to most homebrewers… but of great use to me. It’s also an enjoyable read in its own right, however. It’s a shame that the Mathias book is out of print, and I feel very fortunate having gotten a copy off a German bookstore’s website much more cheaply than anywhere it was available among English-language book vendors online.

2 thoughts on “Yeast, as Understood in 1736

  1. Very interesting and an excellent point about how things will be simplified to not known when they just haven’t been theoretically proven. Stuff about people thinking the earth was flat is a classic example. A lot of pre Pasteur brewing scientists were convinced that fermentation was a chemical rather than biological process and that yeast was a catalyst for this process. So brewers exchanging yeast does not mean that they necessarily understood that the yeast was a living thing although it does show pretty clearly they knew it was essential to the process (You’d have to be fairly thick headed to miss that).

    I’d imagine as brewing became more industrial, some brewers had a pretty good idea how the fermentation process before Pasteur proved their suspensions beyond doubt. But brewers can be a pretty secretive lot and would not be inclined to share their discoveries about yeast with their competitors. Brettanomyces was almost certainly known by Guinness and other big British brewers long before Claussen officially ‘discovered’ it but they had no interest in publishing the secret of the yeast that gave their beers the distinctive ‘British’ flavor. Claussen, working for the lager brewers Carlsberg, had no reason to keep it secret.

    The urinating thing was called leinting, it’s something that I can’t find many references to though, I find it hard to believe the process was wide spread, knowing that human waste isn’t good to eat/drink is a pretty basic level of understanding.

    1. Thanks Rowan, you have thrown some more light onto all this for me, especially with the whole issue of brewery secrecy, which makes sense.

      I’ve seen references to the yeast-as-a-catalyst thing as well (perhaps even in the Zainasheff/White, though I don’t recall it?), and of course, that makes sense given the holdover of ideas from the alchemical paradigm. (Catalysts for transformations, metamorphoses, and so on.) From an alchemical perspective, wort turning to beer would be rather like all those classic transformations used in alchemy, including the idea of turning base metals to gold… and would actually be a very encouraging phenomenon: an alchemist-physician like Paracelsus might easily think, “If we can do with with barley sugar, and such a simple catalyst as barm, we ought to be able to do it with all kinds of materials, including human beings’ living bodies.” Besides, Paracelsus was crazy about fermentation and rot alike.

      Anyway, yes, I suspect by the time they began scaling up industrialized production of porter–which Mathias suggests was more stable in and of itself anyway, would that be because of pH or just greater hop usage?–they would likely have a good (albeit still rough) idea of the fermentation process.

      And yeah, right: leinting. Brrrr. This discussion looks at etymology and suggests the “lant” was stale urine mixed with lime… I wonder if it was that, and not straight piss, that was added to the beer? (As well as to dress wheat seeds before sowing, to keep off the birds.) Here’s another (very disapproving) definition of the word “wash” from a Scottish etymologyical dictionary from 1825, which has a reference to leint ale:

      Screen Shot 2014-05-15 at 3.13.11 PM

      So there you are: “wash-tub” and “wash basin” come from the idea of a tub or basin where urine is collected and staled. Yikes! The word “wash” itself meant urine in the middle ages. I find the idea of adding wash for the purpose of improving color to be weird–malt would have been smoky at that time anyway… but Paracelsus was also a big fan of feces for theoretical reasons: he believed that dung, while fermenting, held a great deal of the generative energy of life. Perhaps some brewer out there had similar notions about urine–that it might help lend life-energy to the process of fermentation?

      In any case, the practice is probably not something I need to touch upon in my own novel… unless some alchemist brings it up in a theoretical context, to the baffled annoyance of anyone in earshot.

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