Increasing yeast alcohol tolerance using Potassium salt

[Chinmay Nayak]

Hey guys,

I was googling around about random stuff when I stumbled upon a mind blowing research article by MIT students. The paper is not very new(2014) but I haven’t seen anyone discussing this in the homebrewing world.

To the research paper

According to the research, a careful addition of Potassium Chloride(KCL) and Potassium Hydroxide(KOH) during fermentation boosts yeast’s alcohol tolerance and alcohol production upto 80%!

I’m not a very scientific guy but to me it means I can make Barley Wine using some of the strains I love but have low tolerance to alcohol. And can also extract much healthier yeast after a yeast wash.

Can someone with better science background kindly shed some light on what to make of it and how to practically use this in homebrewing set up?

 

[LBussy]

A few challenges I see:

• This requires raising the pH (~6.0) of the solution (KOH addition), which I assume would alter the flavor significantly
• Potassium salts are less "salty" tasting than Sodium salts, but they still enhance the ionic reactions on the tongue - impacting taste

The taste threshold (in one test anyway) is said to be ~0.00242 M and 10^-3 (given in the text) is ~0.001 M if my math is right, so not a direct flavor consideration on its face

Generally, though, the character of a Barleywine is due in part to classic yeasts and the stress they are put under to ferment such a beverage. The residual sweetness is critical, and altering the character of that sweetness would be a detriment in my opinion.

By all means, experiment, but this seems like something more suited for industrial ethanol production which feeds distillation, rather than for the creation of a fermented beverage.

 

[Chinmay Nayak]

A few challenges I see:

• This requires raising the pH (~6.0) of the solution (KOH addition), which I assume would alter the flavor significantly
• Potassium salts are less "salty" tasting than Sodium salts, but they still enhance the ionic reactions on the tongue - impacting taste

The taste threshold (in one test anyway) is said to be ~0.00242 M and 10^-3 (given in the text) is ~0.001 M if my math is right, so not a direct flavor consideration on its face

Generally, though, the character of a Barleywine is due in part to classic yeasts and the stress they are put under to ferment such a beverage. The residual sweetness is critical, and altering the character of that sweetness would be a detriment in my opinion.

By all means, experiment, but this seems like something more suited for industrial ethanol production which feeds distillation, rather than for the creation of a fermented beverage.

You are spot on there about saltiness from Potassium creating problems. After posting this, I also happened to consider the effect of introduced alkalinity on a beer, as it can react with some of the aroma and flavour components. Especially hop oils and tannins from the malt.

The study paper also discusses the possibility of using Mono Potassium Phosphate salt for a similar effect, however the impact is smaller in comparison. I think it’s still huge! It was this effect that basically inspired them to experiment further with KOH and KCL.

Do you think MKP can be utilised instead of KOH and KCL to help increase the yeast viability? In fact, my other goal was to increase yeast viability and minimise stress on the cells, without impacting the taste much. So that I can harvest healthier cells for my next batch. My mention of Barley wine was only one example of many opportunities we have in the light of this study.

Also I beg you to suggest scales in “gram per liter” standard since “parts per million” measure is very difficult to understand for me personally.

 

[LBussy]

The study paper also discusses the possibility of using Mono Potassium Phosphate salt for a similar effect, however the impact is smaller in comparison. I think it’s still huge! It was this effect that basically inspired them to experiment further with KOH and KCL.

The results were pretty clear that the impact of raising the pH was a significant contributor. Even if you get away from saltiness, you are fundamentally changing beer.

Also I beg you to suggest scales in “gram per liter” standard since “parts per million” measure is very difficult to understand for me personally.

Be happy I didn't express it in mM. Imagine how challenging it is for a person who learned to measure things in ounces and lbs. All you have to do is shift a few decimals around.

 

[MaxStout]

It would be interesting to see this tested in practice. Brew a batch of wort that's beyond the attenuation capabilities of the yeast under test. Split the batch, with one dosed with the K and the other not. Pitch exactly the same populations of the same yeast, ferment under the same conditions. Measure the FG of both, see which one attenuates more.

Probably not very scientific, and this sort of experiment would be akin to a Brulosophy type of testing. But it might show if this makes a difference when done under typical homebrewing conditions. A yeast "endurance test."

 

[Gnomebrewer]

Also I beg you to suggest scales in “gram per liter” standard since “parts per million” measure is very difficult to understand for me personally.

mg/litre (thousandths in a thousand) is the same as parts per million.
Grams per litre is 1000ppm.
Just shift the decimal point a few places.
It's the beauty of working with metric.