In another post, we’ve told you all about the ancient yeast Raul Cano resurrected from fossilized amber, and the very special pale ale and hefeweizen that were created with it. Now down to business…time for this homebrewer to geek out on what makes this ancient yeast so very unique, and why the entire story is so special to begin with.
It should be noted right from the start that creating beer from ancient yeast was quite a long shot from the very beginning, and Peter Hackett of Stumptown knew this when he signed on to collaborate with Cano on the project. Even though we speak of ale yeast as a species (Saccharomyces cerevisiae), there is a great deal of variation within that species; the very variation that helps gives rise to the plethora of variety present among ales brewed the world over. Many strains of the yeast simply don’t perform well in the hostile environment that is wort, with its alcohol and acidity, not to mention the limited availability of oxygen. Any homebrewer knows that viability (health) of the yeast is very important, even with modern yeast…what effect would 45 million years in amber have on the viability of the strain? The bottom line is, this yeast was very unlikely to create a reasonable beer at all, let alone a critically acclaimed one which Hackett himself said was like nothing he’s ever had before.
To his credit, Hackett decided to press on, and found that this was indeed a very unusual strain. When first pitched, the yeast takes longer than most modern ale yeast to kick in, but when it does – make room. It has a very vigorous, even violent, top-fermenting initial phase that creates a very thick foam at the top of the fermenter. Then it does something I’ve never heard of in an ale yeast. It drops to the bottom of the fermenter, leaving the wort nearly clear. Normally this would be called flocculation and mark the approximate end of fermentation, when the yeast goes dormant to wait for more food (though more accurately a small portion of the yeast would remain in suspension and keep working longer, after other cells had flocculated). But Cano’s yeast doesn’t stop working. It keeps going, fermenting on the bottom of the vessel like a lager yeast would. Eventually, when fermentation slows to the point where the brewer is ready to put an end to it, they “crash” the yeast by cooling it to near freezing temperatures, causing any remaining yeast in suspension to finally give up and flocculate to the bottom so that they can be removed and the beer can be bottled. But here again, Cano’s yeast had other plans; refusing to crash, it simply keeps going – for another month! Apparently a 45 million year nap leads to an epic case of the munchies…
There are two other unique features about the yeast I’d like to mention. One is that it likes to work hot, even for ale yeast. It’s been used in a pale ale that ferments above 70 F, and a wheat beer that ferments at 68 F. My sources suggest that typical temperatures for these two styles would be something around 67 for a pale and as low as 62 for a hefeweizen (though there is some debate that would place it as high as 67, but I’ll go with Jamil Zainasheff on this one). I would speculate that this is because the Eocene epoch from which the yeast hails had a much warmer, tropical climate than the one we currently inhabit, and the yeast was evolved to this climate. My intuition would be that this higher temperature would mean more esters and phenols (fruit and spice) in the finished beer, and tasting notes of others (which were discussed in our other article) seem to bear this out.
Another unique feature is that the strain is apparently unable to digest any but a small range of carbohydrates, far fewer than modern brewer’s yeast. Cano believes this also contributes to the spicy character of the finished beer, though I’m not sure why since I’ve never heard of unfermentable sugar lending a spicy character to beer. On the other hand, unmalted wheat and rye are often described as lending a unique spiciness regardless of the yeast used, so maybe he is on to something. This does remind me of something I read recently about the difference between beer yeast and wine yeast. Apparently wine yeast also works with a smaller range of carbohydrates, and this gives beer made with wine yeast a cloying (overly sweet) finish, unless it is coupled with a beer strain or enzymes are added to the wort to break up the larger carbohydrates into simpler ones. They seem to have gotten around this for the Pale ale by using a lower starting gravity instead – less sugar in the beginning means that even though less is eaten, there is still less residual sugar at the end. A typical pale ale would start at a specific gravity of about 1.058 to 1.065, but the pale ale brewed by Hackett starts at only 1.050, which means that there is roughly a fifth less sugar dissolved in the wort at the start of fermentation.
As for those bottles they intend to roll out to the rest of the country…Cano has patented the yeast strain, and sequenced its genome so that he can enforce the patent. This would prevent unauthorized brewers from conjuring up cultures of the stuff from the dregs of these bottles (apparently Cano doesn’t intend to filter the product). I am ambivalent about this, because while I respect his right to protect his “babies” as he calls them, I’d like to see such a unique strain be as widely available as possible to further the cause of innovation and creativity with its use. However, I suppose this is where homebrewers come in to play; after all, Rogue’s patent on its PacMan yeast hasn’t stopped many a homebrewer from trying their hand with a sample.