Yeast Project: RAM-4 - Brain Sparging on Brewing


Sour beer, saisons, farmhouse beer, homebrewing, ramblings

November 12, 2012

Yeast Project: RAM-4

RAM-4 is identified as a "super-attenuative" saccharomyces strain cultured from spoiled beer from the UK. Although I suspected the strain might actually be brett, on further research tracking down what little information is available about the strains I obtained (at least to my non-biologist, non-scientist resources) it is a saccharomyces strain. It's just not saccharomyces cerevisiae var. cerevisiae. It's something else.

It's saccharomyces cerevisiae var. diastaticus, or sometimes referred to simply as saccharomyces diastaticus. I had never heard of this strain before but by deploying some late night google-fu I found that it is actually discussed in some brewing literature, less so in homebrewing literature, and some scientific work. One article referred to it as a "ninja yeast". Let me tell you why: Saccharomyces diastaticus has a power that saccharomyces cerevisiae usually lacks: the ability to metabolize dextrins and starches. While saccharomyces cerevisiae var. cerevisiae strains can only ferment certain sugars, this ninja yeast can absolutely dry a beer out. Even more than those badass saison strains like 3711. Ok, I thought that was pretty cool. Ninja yeast sounds badass. So why isn't this yeast deployed by brewers, especially those trying to make low calorie beers?

When Boston Beer Co. and Weihenstephan got together to create Infinium beer, one of the goals was to create a very light, dry beer. They contemplated the use of saccharomyces diastaticus, as Weihenstephan has an extensive yeast bank and includes this ninja strain; however, Weihenstephan rejected it because the flavor was unpleasant. (Ultimately, they developed a mash method using un-kilned malt with more enzymes to dry out the wort better. They were limited in options due to the Reinheitsgebot that applies to Weihenstephan. For more information and a look at the patent application, see here.) Further research, including some writings by the well known Charlie Bamforth, explained saccharomyces diastaticus does a great job drying out a beer but produces a lot of phenols, particularly of the medicinal-flavored variety.

(As an aside, part of my research reflected that it is not uncommon to see Torulaspora delbrueckii bacteria used to promote clove flavor in wheat beers. I had never heard of that but I'll probably do some follow up reading on that.)

In fact, saccharomyces diastaticus is a major beer spoiler. Since it can chew up what our average saccharomyces cerevisiae var. cerevisiae leaves behind it almost always has an opportunity to turn your beer into a meal. It is likely the "wild yeast", or one of them, commonly infecting homebrew. I know personally I have had some infected beers that didn't turn sour but did dry out with terrible phenolic character. Saccharomyces diastaticus was probably getting nasty in my beer. Of course, this really goes back towards the argument I frequently make about infections and some of the homebrew folklore that, "the only things that can live in beer is saccharomyces, brett, pedio and lacto." That just isn't true. There is a lot of yeast, mold and bacteria that can survive at different times in the brewing process and many enjoy the anaerobic conditions of a sealed bottle or keg.

Rather than make a lot of medicine-flavored beer, this strain is being looked at for fermentation in ethanol production for industrial/transportation uses since it is able to consume more than other saccharomyces strains but unlike brett, will not take as long or metabolize the ethanol into acid. So that's pretty cool but it doesn't help out my brewing unless I'm brewing beer to run my car -- and I am not.

So bringing all this full circle to the yeast project, I do not intend on experimenting with this strain, at least not yet. I already know what infected beer tastes like, I'm not really in the mood to deliberately make more. So there's really no value in popping this yeast out and letting it loose. I'm not a believer that once a strain gets free in your house it will take over but there's just no value in producing bad tasting beer for the sake of making bad tasting beer. (Your house, equipment and body are constantly covered in a nice layer of yeast and bacteria anyway.) Maybe at some point I will get bored and give it a try but for now the culture will sit lonely in the back of my fridge. I thought the research was far more useful to myself and other brewers so I wanted to share that and explain why there is no test batch for this strain.

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