View Full Version : Feeding Wild Yeasts.

09-22-2016, 08:22 AM
So I've got somewhere in the region of 20gallons of booze in various stages of doneness, 95% made with wild fermentation. I've been reading up on the TOSNA 2.0 protocol and was wondering, would this work for wild yeasts? If so, now here's the doozie, without knowing the particular yeast strains, how would I go about working out the additions in relation to low, medium and high nitrogen needs. I've never fed them before but wanted to give it a go in a 2gallon test batch.

09-22-2016, 09:28 AM
I've done a few mixed ferments with commercial lambic blends (Sacch, Brett, Lacto, Pedio) and feed them TOSNA 1.0. All finished dry with no issues during fermentation.

I've been meaning to do a Brett-only YAN experiment, but haven't had the time and don't know when I would.

09-22-2016, 09:30 AM
Not a chemist but engaging in a thought experiment here. I am assuming that nitrogen is used by yeast to reproduce so if a yeast needs more nitrogen than is available the yeast's ability to bud will be inhibited. If the yeast has sufficient nitrogen (all other things being equal) it will reproduce effectively producing a "maximum" (I am supposing) number of cells. If the yeast has an excess of nitrogen I am assuming that its ability to bud and reproduce will remain unaffected being unable to make use of the excess of nitrogen. (I am assuming that too much nitrogen does not create other problems). So how to determine how much nitrogen an unknown strain of yeast needs?

If I were you I would take three samples of the yeast culture and treat the first sample as if it had a low need for nitrogen, the second sample as if it had a medium need for nitrogen and the last sample as if it had a high need. I would then supply each sample with the same amount of sugar and an appropriate dose of organic nitrogen for these assumed needs and then count the number of cells in each sample at specified times. A high need yeast with access to too little nitrogen will produce fewer cells than a high need yeast with access to more nitrogen, and a low need yeast with access to low amounts of nitrogen will not produce any fewer cells than if that yeast were provided large amounts of nitrogen.
But , absent the equipment needed to count the number of cells I am not sure how you can determine the needs of your strains of yeast. But as I say, I am not a chemist (I am social scientist) and others may have a very different approach to your question - and indeed, I may have the cat by the wrong tail: perhaps nitrogen has many other functions than simply allowing the yeast to optimally bud...

09-22-2016, 11:16 AM
This was lifted from Wikipedia. It's one of the reasons that made me ask about nitrogen feeding. However, I suppose as there's not a weight to the amount of wild yeasts added, as there is in commercial yeasts (per 5g packet), is it possible to add too much nitrogen if using TOSNA protocols for high nitrogen needs.

This piece lifted from Wikipedia re over feeding nitrogen-
Nitrogen supplements, particularly DAP, stimulates yeast reproduction and can greatly increase the biomass. This could have the consequence of speeding up the fermentation rate faster than what a winemaker may desire and will also increase the fermentation temperature due to the heat being generated by the yeast. The excess biomass can also create a scarcity of other yeast nutrients, such a vitamins and sterols, due to increase competition and may lead to the production of off-odors (such as hydrogen sulfide) and even stuck fermentations.

09-22-2016, 01:58 PM
This is interesting. But could you not still feed test batches of yeast different amounts of nitrogen and monitor those variables (temperature , speed of fermentation, hydrogen sulfide production etc to obtain the optimal feeding regimen for your yeast.

09-22-2016, 04:29 PM
It's possible, I think it means isolating the various yeasts onto their own Petri dishes and then taking three samples of each and feeding them the three amounts of nitrogen as suggested through TOSNA. Or feed them as a whole, as you suggested.
In theory the high leela of nitrogen should be fine as there's bound to be low, medium and high nitrogen need yeasts in the batch.