Yeast Quantities

Hi all,

Been wondering about how recommended yeast quantities are calculated - I only had half the recipe quantity on hand on my last wash and am way too impatient to wait until I get more so just went with what I had. seems to be doing ok.

My limited understanding (half remembered from school biology classes a few decades ago) is those little yeasties multiply pretty quickly - so event a small amount should then be able to scale themselves up effectively to deal with the wash. Is the proportionally larger quantity in larger washes mainly to ensure the desired yeast out-competes any wild guys in there?

Comments

  • Easiest answer is that underpitching will emphasize yeast character, good and bad, while overpitching will deemphasize.

    Example - if you were using an ale yeast known to produce fruity esters, underpitching would create more esters, overpitching would make less.

    Also, in a highly stressful ferment, underpitching can sometimes lead to a stalled ferment.

    Heavy overpitching can lead to feinty/tailsy distillate if you distill with yeast.

  • edited November 7

    Let me rephrase it.

    Extreme Underpitch - High risk of bacterial/wild yeast contamination and stalling. Very slow fermentation.

    Underpitch - Emphasize yeast character (congener formation), Smaller risk of contamination and stalling.

    Normal Pitch - Balance of yeast character and risk control.

    Overpitch - De-emphasize Yeast Character, insurance against stalling. Can be sulfury in low-nutrient environments. Can cause temperature spikes in non-temp controlled fermentation.

    Extreme Overpitch - Feinty/Tailsy character if distilled with yeast, reduced yield. Very fast fermentation, will spike temperatures significantly, which if not controlled will cause faults. Impact to yeast viability if re-using yeast.

  • edited November 7

    So to give two real world examples:

    If you are wanting to make neutral, you might chose to slightly overpitch, compensating with additional nutrients, and you might want to ensure you maintain cooler fermentation temperatures. This will reduce the flavor impact of the yeast, ensure out-competing bacteria, and ensure a fast fermentation with little risk of stall.

    If you are wanting to make a high character whiskey, you might use a yeast strain known to produce interesting congeners, English Ale, Hefe, etc etc, and purposely underpitch, while attempting to induce more yeast stress by fermenting at a slightly higher temperature - all to emphasize the yeast character in the final distillate. To counterbalance the stalling risk, and risk of lower yields, you might choose to not push the starting gravity too high.

  • Mrmalty.com has a great pitch rate calculator, but is on the high side, he is about 2x higher than Arroyo in billions of cells per ml...

    and remember, they multiply in the presence of oxygen, but make alcohol when it is absent...

  • @grim @CothermanDistilling thank you for your wisdom :-)

    My underpitched TPW destined for neutral may not have been my brightest idea then.

  • It’ll be fine

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