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zadvocate

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I had my first case of H2S with my pinot this year. I read that it can be caused by stressed yeast. I rehydrated with GoFerm, used a dose of Fermaid O at the first sign of fermentation, and a dose of Fermaid K at 1/3 sugar decrease.

So I was reading the Scott Labs handbook and it seems their recommendations are different than what I have been using (got mine from more wine).

I am not able to measure Yan but with a must of 25 brix or higher, they reccomend the upper limit recommendations. Scott and More wine both say 1.5 grams per gallon for Fermaid o but it is the second dose of Fermaid K that does not jive. Reading the Scotts Handbook it calls for about .90 grams per gallon on the second dose.Whereas Morewine calls for 1 gram but that would be split up into 2 doses so .5 for the second dose. So essentially it seems that a must with probably a high yan(brix were 28 then I diluted to 25) required almost double the dose of Fermaid k. Just wondering if this is correct and possibly the cause of my H2S.

With 11.4 gallons of must I added

Fermaid O #1 8.55 at end of lag
Fermaid F #2 5.7 after 1/3d sugar depletion From above it should have been 10.26

Do these number make sense?
 
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stickman

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General nutrient additions indicated on packages etc. are only estimates based on some average must starting YAN. Usually these estimates work reasonably well helping to avoid H2S and stuck ferments, even though most of us don't know the starting YAN.

I've always used the BSG nutrient information and have developed a spreadsheet, so that's what I'll use here for comparison. The spreadsheet works for Fermaid K, because Superfood and Fermaid K have the same nitrogen content.

The fact that your must was watered back from 28brix puts it at a fairly high risk with a suggested total YAN of 350ppm. Assuming some average starting must YAN of 200ppm, I calculate approximately 21g Fermaid and 21g DAP needed total. In this case, the suggested method of addition is to split the total into 3 doses, inoculation, 3 to 4 brix drop, and the last addition at around 10 to12brix.

But as earlier stated, even this calculation is an estimate, because we don't know the starting YAN. If a grower indicated the expected YAN is low, it may be below 100ppm to start.

@NorCal and some others have started using the non-H2S yeast, and so far, have had good results adding just a standard dose of nutrients.
 

NorCal

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Well said @stickman. We have had ferments resulting in H2S and I believe it comes from nutrient deprivision and high heat. We switched over to Andante the last two years and have had no signs of H2S.
 

balatonwine

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H2S can also be caused by residual sulfur on the grapes from spray. More common in places like California where sulfur is more routinely used, to combat powdery mildew. Adding yeast nutrients will then not help much if the selected yeast is susceptible to creating H2S, and the only solution is to either guarantee no sulfur residuals on the grapes, or move to a non-H2S producing yeast.

When I first started making wine, I had H2S production. I traced it all back to residual sulfur spray. I even routinely use Montrachet without any problems now, after controlling for sulfur spray, do no YAN ("yeast assimilable nitrogen" for any new wine makers here) correction and have no H2S problems.
 
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