After having spent far too much time trying to reason with the presence of spent grains and pulses in the ancient Armenian beer, I was struck with an idea that I decided to test. I will outline the essential experiment, logic, and defense in this post.
Problems with Fermenting Non-strained Wort
-The grains do not float except during fermentation
-The grains occupy a large amount of the fermentation vessel
-Laziness/ignorance (i.e. not straining) is not an adequate excuse for not straining, especially when the benefits of having extra space in the fermenting vessel are obvious
For these reasons, I was convinced there must be a functional (real or imagined) reason for the presence of spent grains and pulses in the fermenting wort. Certainly, this extra “food” would help with the fermentation by bacteria and other non-yeast critters that are present. But, it certainly will not contribute such a substantial amount of extra “food” (sugars, etc.) as to make up for the inefficiency of vessel space.
At some point, I had the following idea: perhaps the spent grains from a previous batch served as a yeast starter that helped to initiate fermentation in subsequent batches. I decided to test this and subsequently made a 1/2 gallon batch of wort and pitched 1 cup of grains from the bottom of the fermentation vessel of a previous batch. Fermentation kicked off within 12 hours and the yeast/trub on the older grains ripped through the sugars of the new batch. It was clear that this technique requires only a small amount of grains to be left in the fermenting vessel from each brew day.
Benefits of this Fermenting Practice
-It offers a functional reason for the presence of grains in the Armenian beer
-The concept is very similar to sourdough starters, a (likely) familiar practice to the ancient Armenians. Thus, the beer-practice is relatively intuitive
-Fermentation would be more consistent among batches; i.e. the uncertainty/inconsistency of spontaneous fermentation could be avoided
-A house “yeast” character could develop and bacteria eventually removed by natural selection
-The grain-trub-yeast could be stored for a period of time before reuse; thus, a factory-like or continuous production of beer is not necessary for repitching, a la pitching krausen (yeasty foam) from a previous batch
-It would offer more yeast for immediate fermentation compared to yeast living in the porous walls of ceramic fermenting vessels (another method of fermentation)
I plan to continue this line of experimentation with the grains from the spontaneously fermented pulse beer that I made last week. I am interested to see how well this spent-grain fermentation process (SGF) works with wild yeast. I am also interested to see if this process can select for the yeast at the expense of the bacteria/molds in the wort.
Call for Help
Have you heard of this technique being practiced by anyone – historical or modern? Do you have any sources that reference this practice or other ancient fermentation methods (besides the north European wood stirrers, Egyptian krausen pitching, spontaneous fermentation, and yeast-borne ceramic vessels)? Or, are there any general thoughts about the SGF method?