Seeking very low ABV yeast for Kvass and "soda" experiments...

[Paul_F]

I've only brewed meads and ciders so far, but have started getting interested in brewing Russian Kvass (or Kvas, there seems to be some dispute on how to translate it...). I've also thought idly about trying to "brew" some "hard soda" type beverages.

So, as much as a thought experiment as anything else, I'm wondering what yeasts there are that have notoriously low alcohol tolerances? I know that typically, in order to make a sweet-ish beverage, one just adds more sugar in whatever form than the yeast can handle, leaving retained sugars... but if ones goal is for something UNDER about 3%, as much for bottle carbonating as for the alcohol, what yeasts "poop out" that early?

I know there are other ways to "force" the yeast to "poop out", like pasteurizing, sorbating, etc... but I want to focus on yeast selection, before going into those "later stages".

Thoughts, anyone?

 

[mediant]

Kvass is traditionally made using sourdough bread starter, with emphasis being made on lactic fermentation, so regular bread yeast plus lactic starter will do in a pinch. In order to meet the low ABV specification (about 1.2%) , fermentation is terminated prematurely by chilling until the yeast drop out. At factories they filter the remaining yeast out, at home it's usually enough to keep the kvass in the fridge since that moment. Then the drink is sweetened, left to carbonate lightly and consumed quickly as the shelf life is quite short - a week or so (unless you choose to go into "later stages", as you said).

 

[dmtaylor]

The least attenuative yeasts (I have used all of these) that are commercially available are: Windsor, Munton's, and Wyeast 1099. I believe these three yeasts might all be the same source or nearly identical. Expect attenuations in a standard malt wort to max out at 58-62%. This is, however, due to their limited ability to ferment complex sugars, NOT due to alcohol intolerance. If fed simple sugars like in a soda, I think they would attenuate closer to 100%.

For kvass (which, incidentally, I have made before), selection of yeast is not so important because the lack of attenuation is not so much due to lack of fermentability or alcohol intolerance, but more due to the process wherein bread is soaked in hot water, ran off, and then the yeast (whatever yeast you choose) is requested to ferment the starch soup that has been generated. There's mostly just starch and little sugar in bread, so there's not much sugar there for the yeast to eat, no matter what yeast you use. This results in a beverage of about 1% ABV maximum.

Soda is a totally different story! For that, the use of those low attenuating yeasts is actually a pretty good idea, I think, especially used alongside some sorbate (very necessary) to severely injure the yeast and prevent it from going overboard, which, it might anyway. I have made soda before only using one of those boxed Root Beer kits, and these kits come with special caps that have rubber vents that will allow off-gassing at an appropriate rate to allow carbonation but also to prevent explosions. If bottling in glass, be very, very, VERY careful. I would recommend bottling in plastic, or kegging, not glass.

 

[bracconiere]

For kvass (which, incidentally, I have made before), selection of yeast is not so important because the lack of attenuation is not so much due to lack of fermentability or alcohol intolerance, but more due to the process wherein bread is soaked in hot water, ran off, and then the yeast (whatever yeast you choose) is requested to ferment the starch soup that has been generated. There's mostly just starch and little sugar in bread, so there's not much sugar there for the yeast to eat, no matter what yeast you use. This results in a beverage of about 1% ABV maximum..

I can vouch for that.. from my experience with failed sake. never could get the koji to convert it, but it did have like 1% alcohol in it, just with the yeast fermenting steamed rice...