Purposefully stressing yeast

This advice is always funny to me. Underpitching yeast can be beneficial for a lot of styles. What I was taught in school was for ales: .75 million cells/ml/P and to go up to 1 million for wort above 15* Plato. Normal time from beginning of fermentation to terminal gravity should be 2-4 days for an ale. I do yeast cell counts for every beer I brew and I follow this guideline normally. However, for NEIPA's, I decrease the cell count. Same for hefeweizen's and when I brew the occasional Belgian style.

For homebrewers, I frequently see people saying they're using a starter and reaching terminal gravity in 7-10 days. If that is the case, you are almost definitely already "underpitching" or not aerating enough. If you then "intentionally" underpitch, you will be going far beyond what most brewers would recommend.

 

Permit me to say that yeast nutrition could be a factor as well. Having a healthy fermentation is not just a function of yeast count and oxygenation amount.

Cheers!

 

I think most of the original confusion would have been avoided if the LHBS worker simply said "do these things to maximize ester production" rather than saying "do these things to stress the yeast".

 

I am not a fan of purposefully under-pitching. Ever. You are just never going to get a repeatable result that way. Temp and such to a certain amount I can understand. Under-pitching is just too much of a crap shoot as to what it does.

 

Yes, a factor I frequently forget since I don't have to think about it. Commercial yeast pitches are shipped so fresh and with nutrient rich wort and I never use yeast more than a week after harvesting without feeding it.

 

Disagreed. If you use a consistent pitching rate, consistent aeration amounts, and all else remains the same, you will have consistent results. To do so requires more time and equipment than most homebrewers will care to spend.

 

My preferred liquid yeast is Wyeast and I always make sure to 'pop' the inner pouch since it includes yeast nutrient.

I frequently homebrew using dry yeast (benefits of cheap and easy along with high quality). I make sure to add some yeast nutrient with 10 minutes left of the boil.

Wort has most of the 'things' that yeast need with the exception it is deficient of zinc. Below is something that Kai Troester wrote on his blog:

"Zinc is an important co-factor in many enzymes and thus a requirement for yeast growth. Most yeast strains require 0.1 – 0.2 mg/l of zinc. Zinc levels greater than 0.6 mg/l can inhibit yeast growth (Priest, Handbook of Brewing).

Zinc may be the only yeast nutrient that even barley malt is deficient of."

Cheers!

 

Maybe if you only slightly underpitch.

 

Wait... you're pitching .75 million cells/ml/P with fresh, I say fresh yeast? Everyone knows that's only the appropriate pitch rate when re-using yeast. <JK>

 

Below is what Jamil Zainasheff writes in the Mr. Malty FAQ:

“According to both White Labs and Wyeast, a White Labs Pitchable Yeast vial and a Wyeast ACTIVATORTM 125 XL Smack Pack both contain an average of 100 billion cells and are enough to pitch directly into 5 US gallons (18.9 liters) of an ale wort at 1.048 SG (12°P). This is a pitching rate of 5.3 million cells per milliliter, which is close to the pitching rate many professional breweries begin with when starting a new pitch of ale yeast.”

<not JK>

Cheers!

 

Many professional breweries make bad beer. Just sayin'

Seriously, what pitch rate in cells/ml/P do you use? Just thought I'd skip to the end of the discussion.

 

I remember either seeing a video or reading an article by Chris White where he advocated for lower pitching rates for homebrewers saying that commercial brewers pitch high rates to ensure that the yeast would outcompete contaminants. If I remember correctly, he said that the increased ester production was pleasant. I tend to disagree, but obviously it's personal preference. I do believe that harvesting yeast from an underpitched batch is a much worse practice than underpitching first generation yeast.

All that said, I do not know very many professional breweries that do yeast cell counts. I would estimate that less than 10% of small production brewers do so and it has a huge noticeable effect on the quality of beer being produced these days. Some brewers don't do counts and have learned procedures that work for them, but that experience takes months and frequently results in new breweries producing subpar beer

 

The most common general practice I've come across, with regards to brewers that don't do counts, is to pitch 1 gallon of healthy slurry per bbl of wort. That's a safe over pitch in most worts.

 

That is huge! When harvesting American Ale Yeast at my old brewery, 8 gallons of slurry was all I needed for 30 BBL of 15°P wort. That said, a lot of brewers wait until after cold crashing and in some cases until after transferring to harvest resulting in a lot of dead yeast.

 

Actually, are you sure that shouldn't be 1L per BBL? White Labs and Wyeast typically recommend 1l/bbl if a brewery purchases direct pitches without yeast starters

 

I'm talking about harvesting and reusing slurry, not about gen 1 lab pitch slurry. For the latter, 1L per bbl is the common pitch rate.

 

Interesting. I never had to go even to 1/3rd of that volume on a harvest. I would always harvest yeast the day after the beer hit terminal gravity and reuse within a week. If I had to go longer, I'd feed the yeast some concentrated wort. Keep it vented and stirred.

 

Yup, more yeast amount should be used when reusing yeast than 'new' yeast to ferment a batch of beer.

Cheers!

 

And not many homebrewers perform yeast counts either. As you are well aware, without an accurate yeast count there really is not a way to know with certainty what amount of yeast cells or pitch rate is truly employed.

I have had several conversations with microbiologists and there input is that it takes a quite a bit of experience/skill to perform a methylene blue yeast count and even with trained personnel there is a nonsignificant error bar associated with the ‘answer’.

Cheers!

 

I do not perform a methylene blue yeast count in my homebrewery.