At what stage does yeast use potassium?

[piojo]

Does yeast need potassium during growth, or during anaerobic fermentation, or both? Or worse, do they want it as soon as possible when pitched?

I ask because the popular BOMM mead recipe suggests adding potassium carbonate at pitch to provide potassium and buffering, and I'm thinking about using potassium hydroxide instead.

I can't add it all an once because it would raise the pH too much. Do the yeast need their potassium right away? My plan is to finish adding KOH by the time I finish adding nutrients.

Edit: potential benefits are: a bottle of 4M (around 22%) solution will last forever, and the amount that fits in a popular syringe size is exactly the amount I'll need for a bucket-sized batch (20-30 mL). It'll dissolve immediately and won't need measurement except drawing it into in the syringe. Risk management: 22% KOH will burn skin and eyes, so I will wash the outside of the syringe immediately after filling it, and I will use eye protection at all times.

 

[Silver_Is_Money]

Potassium purportedly begins to become detrimental to yeast health at some level. As low as 10 ppm pops into my mind. That said, it is commonly added in the form of Potassium Metabiulfite to rid water of chlorine and chloramines, and also as an oxygen scavenger. I just added 0.3 grams of K-Meta to 9.3 gallons of no-sparge water for a Stout I'm brewing, to scavenge oxygen. I'm also aware of several brewers on this forum adding KCl for its chloride component, and having good results. So perhaps the 10 ppm warning doesn't hold water?

 

[ESBrewer]

Yeast probably needs some potassium all the time, as potassium concentration plays so many key roles in all living cells. A couple of millimoles per liter would be typical in many physiological, extracellular solutions but I don't know how much is too much and how little will be enough to make mead. I think yeast cell (unlike human cells) is able to survive in wide range of potassium concentrations, but it may not be fermenting happily if you go to the extremes.

In pot.metabisulphite only ~one third of the mass will be potassium so 0.3grams contains roughlu 0.1 g of potassium and 0.1g / 40g/mol = 0.0025 mol and in 9.3 gallons this is equivalent to about 0.0025mol/(9.3*3.785l) = 71µM potassium only. This is about 2.7ppm. When brewing beer, grains/wort always contain some potassium (there is ~2.5 grams per kg in barley), but in a mead there is probably less endogenous potassium available in the must.

 

[piojo]

I've googled this several times in the past several months, and I've come to the conclusion that yeast don't need any more potassium than what's in the must and in the nutrient you add. The recipes that say to add potassium do so solely for buffering, and it often detracts from the final flavor. In particular, the Scott Labs handbook says nothing about potassium supplementation. I am going to stop adding it.

 

[thehaze]

I used KCl as a way of adding Cl without raising Ca, in my latest IPA. The mash water had more than 25 ppm K with no detrimental impact on flavour. From an email exchange with a prolific brewer in UK, I found out that Mg and K actually help with the mouthfeel.

 

[Silver_Is_Money]

I used KCl as a way of adding Cl without raising Ca, in my latest IPA. The mash water had more than 25 ppm K with no detrimental impact on flavour. From an email exchange with a prolific brewer in UK, I found out that Mg and K actually help with the mouthfeel.

Using KCl to boost Cl- ion concentration for NEIPA's seems to be somewhat common. And no one has complained of off flavors due to potassium to my knowledge.

 

[thehaze]

This IPA I brewed was a sorta hybrid: High-ish Cl, low SO4, no adjuncts - just lager and pale malt -, dry hopped for 2 days after fermentation was finished - no biotransformation. So not quite a NE, although hazy, but to stick to the subject, I added K to the beer in form of KCl and several people, including me, have not noticed off-flavours.

 

[piojo]

The background for this question was that some people advocate adding potassium carbonate to mead, both for buffering and for the potassium. But the amounts are huge: 150-300 ppm molecular potassium. It doesn't give off flavors (it's fine), but it dampens the sourness that should be present to counteract the sweetness (if it's still sweet after fermentation).