Sorbates in beer? Ways to stop yeast

[SanPancho]

So I’m wondering about how to stop a diastaticus strain. I know sorbates actually stop multiplication and not necessarily fermentation 100%, but im wondering if that’s enough? I also was told sorbates don’t work in beer as the ph is too high. Anybody able to confirm or refute that?

I also thought about dumping in some sugars and a killer strain like cbc/f2. Im assuming that’s another option? Curious to know how much sugar and yeast id need to pitch in that scenario

 

[RPh_Guy]

Heat pasteurization is an option if you can figure out the logistics, but it might damage the beer.

Sterile filtering (0.45 micron) is a good option, but you'd need to invest in the filter or filters and a pump that can move lightly-carbonated beer (e.g. diaphragm pump)... if you don't have those things already. The beer would need to be clarified beforehand to avoid clogging the filter.

Sorbic acid is indeed less effective at higher pH because it's the undissociated form that is active, and its pKa is 4.75 (the point at which 50% is undissociated). However, it should still be effective at normal beer pH, especially if the beer is closer to pH 4.0 and you use the maximum amount allowed by regulation (300ppm sorbic acid = 405ppm K sorbate). For greatest efficacy you may consider lowering the beer pH with phosphoric acid or other mineral acid.

The beer needs to be warm (room temp ~68-72°F) when adding the potassium sorbate because it has poor solubility at lower temperature.

For best results, the beer should be clarified (to remove the yeast) before adding the sorbate. If the yeast population is too large, it won't work.

If the beer has other contaminants, that could be a problem because lactic acid bacteria create a geranium-like off flavor by metabolizing the sorbic acid.

Adding killer yeast would be unlikely to work in my opinion.

Cheers

 

[Rob2010SS]

Someone on this forum once told me that if you add potassium sorbate AND a campden tablet, it'll deactivate the yeast and keep them from fermenting. I have done it a couple of times to add maple syrup in the keg and then bottle from the keg and it seemed to work. (By saying "seemed to work", I kept the bottles in a warm room and only refrigerated the ones I was going to drink immediately and I didn't have bottle bombs, is what I mean...).

@RPh_Guy and others are definitely more knowledgeable than I am on the scientific part, so my opinion will stop here.

 

[SanPancho]

The sorbate stops them from multiplying, but the meta is just antioxidant if I recall correctly. Its mostly a wine and cider thing as I understand. Not too familiar on that side.

Still trying to decide if I wanna do sorbates or a killer strain like f2.

 

[RPh_Guy]

campden tablet

meta is just antioxidant if I recall correctly. Its mostly a wine and cider thing as I understand.

Right, sulfite does not inhibit microbes at normal beer pH. It does inhibit microbes in wine and cider where the pH is lower, in addition to providing anti-oxidant effects.

 

[Rob2010SS]

The sorbate stops them from multiplying, but the meta is just antioxidant if I recall correctly. Its mostly a wine and cider thing as I understand. Not too familiar on that side.

Still trying to decide if I wanna do sorbates or a killer strain like f2.

So what is killer yeast? Never heard that term...

 

[RPh_Guy]

Some strains of Saccharomyces spp. produce compounds that inhibit other [susceptible] strains of Saccharomyces. The compounds are called competitive factor or kill factor, and the yeast that produce then are called killer yeast strains (normally wine yeast).

Whether the contaminating strain of Sacc is susceptible to kill factor in this case is uncertain; it's certainly possible for wild strains to produce competitive factor and/or be "neutral" to it.
How much growth by a killer yeast and under what circumstances is needed to produce enough kill factor to inhibit susceptible strains is also unclear. Literature on kill factor is generally lacking. Intentionally inhibiting fermentation by a particular strain seems to be completely untested. That's why I have doubts whether it would work, certainly compared to tried and true methods like using sorbic acid.

 

[SanPancho]

It works. Used in bottle/can/keg conditioning for this very reason.

as for dosage, that’s the part I don’t know.