# DAP toxic?



## Tall Grass (Nov 24, 2009)

Scanning through a few supplier websites this evening and I ran across this and it has me wondering...



> DIAMMONIUM PHOSPHATE (DAP) (Nutrient)
> DAP usage is 1/2 pounds per 1000 gallons
> 1.13 grams per 5 gallons
> 1.13 grams is about a heaping 1/4 teaspoon PER 5 gallons *Add at 1/3 sugar depletion as it can be toxic to the yeast if added during the yeast re-hydration stage and the early fermentation stage when the yeast population is low*.



I've been adding DAP (nutrient) and energizer to my wines right at the beginning (before sprinkling the yeast on top.) But, could that combo be TOXIC to the yeast ? I've never had any problems doing it this way ....


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## Stu (Nov 24, 2009)

Tall Grass,

Adding DAP to the water that you rehydrate your yeast in is definitely toxic. When freeze-dried yeast are rehydrated they are unable to regulate what chemicals pass through their membranes, because the membranes are dessicated. Once the membranes are rehydrated they function normally and are able to regulate this flux, so anything in the yeast rehydration water goes directly inside the yeast cells.

There are some yeast-rehydration nutrients (Go-Ferm, FortiFerm) that are meant to be dissolved in the yeast rehydration water before the yeast are rehydrated. These chemicals give the yeast some increased protection in cases of high sugar / alcohol.

As for DAP additions early in fermentation, it's a good idea to add DAP a day or so after inoculating with yeast. Freshly inoculated yeast first acclimate to their high-sugar environment, then begin increasing their population before they begin fermentation (this is the lag phase.) Dried yeast have plenty of N available to them from the manufacturing process, so adding it early can make the concentration too high.

Also, adding DAP early can inadvertently feed wild or spoilage organisms.

If you're a wild-yeast fermentor (I fall into this category) you should wait until your Brix drops by about 10%, then make your DAP / nutrient adds.

Good luck!

Stu


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## Wade E (Nov 24, 2009)

I dont use it with my rehydration water but do add it immediately with my must which I guess isnt the problem.


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## sjjan (Oct 29, 2022)

What is the latest moment in the primary fermentation you can still add DAP to solve H2S problems?


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## Rice_Guy (Oct 29, 2022)

* if you have H2S you have passed the point.


sjjan said:


> What is the latest moment in the primary fermentation you can still add DAP to solve H2S problems?


The current look at yeast growth is saying that there are stages; 1 lag where the population gets established, 2 exponential growth, 3 flat growth plateau/ metabolism where something is limiting, 4 decline or senescence/ something is missing or toxic

The suggested time to fix a nutrient issue is toward the end of exponential growth or right at the beginning of flat growth. Since we’all don’t check population every day with a cell counter this is normally defined as 1/3 sugar consumption. ,,, Note that the original post was about DAP. The limiting nutrient could be oxygen or sterols or magnesium etc. To prevent wild growth followed by a crash current recipes suggest organic nitrogen as Fermaid O followed by Fermaid K at one third sugar consumption. If you check TONSA calculators you will find more on nitrogen/ feeding yeast


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## sjjan (Oct 29, 2022)

@Rice_Guy Thanks!

Well, yes, I had to go to Africa for work and thus could not taste the ongoing of the primary fermentation of 2 wines. One of them is at 1.023 and the other at 1.004, and both have a light H2S issue. I would assume it is too late to add a bit of DAP now and would have to fix this another way. So what remains is a bit of copper? Would it help to add some (I know, the dose is minimal or otherwise could be toxic) already during the fermentation? Or just wait until the juice has settled and cleared out?


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## David Violante (Oct 29, 2022)

My understanding is that splash racking would be very helpful, and kmeta as well, for the one so close to the end. Otherwise I would use Fermaid O if you have any. I would steer clear of copper unless you have to, and use something like redules if you can get it. There’s a pretty interesting discussion on Nutrients and when to add in the *This Years Crush* thread. Folks there also relate it’s ok to use DAP near the end as long as some fermentation is going on. TOSNA approach is best throughout but it doesn’t seem like you and the ability to do that with your trip. I used DAP on my saignee near the end and it seemed ok. They just don’t have enough nutrients it sounds like. I believe both @crushday and @winemaker81 recently had some H2S issues and if I remember right splash racking helped quite a bit.


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## winemaker81 (Oct 29, 2022)

sjjan said:


> What is the latest moment in the primary fermentation you can still add DAP to solve H2S problems?


Adding nutrient won't solve a H2S problem -- it may keep it from worsening.

I trust @Rice_Guy's explanation is correct. If the SG is at or above the 1/3 mark, e.g., OG was ~1.090 and currently at ~1.060 or above, I'd add a 1/3 dose of nutrient. For this example, if the SG was between 1.020 and ~1.060, I'd add a correspondingly smaller amount of nutrient. If there is any growth occurring, this will remove the nutrient stress. Note that I can't tell you this is factually correct, but it's what I've done and it makes sense to me. Yeast doesn't play by the rules we set for it, so I cover things as best I can.

Treating H2S is a different effort. First -- stir the heck out of it and/or splash rack. This dissipates the H2S, which prevents it from forming mercaptans in the wine, and introduces O2 the yeast may need. Run a fan -- the "aroma" is noxious. H2S is also flammable -- the concentration coming off the wine is supposed to be low enough to eliminate a fire problem, but I'd reduce the chance to zero by running a fan in a ventilated are and not having any open fire sources.

Add a double-dose of K-meta. K-meta works since free SO2 bonds to contaminants and renders them harmless. The K-meta will reduce the problems, including addressing excess O2.

I had a whiff of H2S in one of my batches a few weeks ago. I reacted IMMEDIATELY by doing the above -- added more nutrient, dosed with K-meta, and stirred the heck out of it (it was grapes, not juice, and this was an effort). I caught it very early -- the "aroma" of H2S is unmistakable, once you smell it, you won't forget it, no matter how much you wish! In this situation, the problem was eliminated.

If this process doesn't eliminate the H2S after 2 days, use a product such as Reduless. This product introduces a measured dose of copper that will handle any remaining H2S. Use a fining agent after a couple of days to force precipitate the copper. I recently read that bentonite is best, although I used K&C when I had 14 gallons of H2S wine (couple of years ago).

If mercaptans form (ugly aftertaste), the treatment is ascorbic acid. Ascorbic is VERY strong -- I calculated how much I needed, and used a 1/4 dose. This actually worked, but it took 6 total months to treat the H2S in my large batch.


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## Rice_Guy (Oct 29, 2022)

sjjan said:


> One of them is at 1.023 and the other at 1.004, and both have a light H2S issue. I would assume it is too late to add a bit of DAP now and would have to fix this another way. So what remains is a bit of copper? Would it help to add some (I know, the dose is minimal or otherwise could be toxic) already during the fermentation? Or just wait until the juice has settled and cleared out?


The tool I would use here in the states is a product called Reduless. It is copper bonded to yeast cells. I don’t know if you have access to that on the continent. This treats the wine then is racked off in a day. What else, ,, if mercaptans can be tasted (meaty and some bitter) you can reverse this by adding vitamin C. (Ascorbic Acid)
If you are running serious volume as 500 liters I would measure copper sulfate, so that dosage is controlled. If the quantity is low like a 20 liter carboy the copper metal sounds OK, ,,, copper is toxic in quantity.


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## sjjan (Oct 30, 2022)

It is 600 liter of young wine. The fermentation is not done yet. Not sure if we can get Reduless, but I do have copper sulphate. I know this stuff is poisonous. I would be tempted to use some DAP for the wine that is at 1.024 )or lower now) but this might already be too low with an alcohol percentage too high already. Splash racking might help but brings risks with it as well. In any case I would have to wait until the primary fermentation is completed, right? Thanks for your advise @Rice_Guy


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## winemaker81 (Oct 30, 2022)

sjjan said:


> Splash racking might help but brings risks with it as well. In any case I would have to wait until the primary fermentation is completed, right?


If you have H2S, you have an immediate problem. All potential risks are now secondary.

If caught early, the H2S can be driven off by vigorous stirring and/or splash racking. Adding K-meta addresses anything that isn't eliminated by the stirring/racking. If caught early, you are now done.

If the H2S is present long enough, treatment with copper is required. As everyone notes, this is a risk as copper is toxic to humans.

If the H2S is present long enough, mercaptans form. This ruins the taste of your wine, and requires treatment with ascorbic acid, which is a strong acid. Overdose, and your wine is too sharp, and you have a new problem to treat. Plus, at least in my situation, it took months to resolve, not knowing if it was working.

H2S is the one thing in winemaking that requires immediate responsem.


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## sjjan (Oct 30, 2022)

@winemaker81 yes, it is a problem to be dealt with. I agree. But what to do with the ongoing primary fermentation? In other words. 600 liter is I think too much just to stir and get it sorted. Any suggestions are more than welcome! Don’t get me wrong. I was for work in Africa for 2 weeks and added some DAP according to schedule. I can measure YAN and apply DAP to schedule. It is just falling short now that I am back home again. Work (in Africa) had to go on, but for the winemaking part, it would have been better to stay home. Luckily it is just one batch. The rest is all fine and fermented to dryness. And the wine was all cooled with glycol coolers so slowly fermenting.


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## winemaker81 (Oct 30, 2022)

sjjan said:


> @winemaker81 yes, it is a problem to be dealt with. I agree. But what to do with the ongoing primary fermentation?


Stirring will not hurt the fermentation, and if you're using good yeast, at this point in the process a dose of K-meta is not likely to have much effect on the yeast.

Two weeks ago I caught a whiff of H2S in a batch (much smaller than your 600 liters), and immediately added nutrient (batch wasn't as far along as yours), double-dose of K-meta, and stirred as best I could in a thick must. As near as I can tell, the yeast completely ignored the K-meta. Of the 4 equal sized batches in production at that time (all ~40 liters), the infected batch finished first or second.

I'm actually surprised, as I expected the ferment to stutter, but it didn't. [Nope, not complaining!]

If O2 is a concern? You're in fermentation, so it's not really a concern. My batch a few years ago was caught during the first post-pressing racking, so H2S had time to do damage. I stirred the heck out of it (54 liter batch), and today the wine is fine. K-meta handles O2.

If your concern is the K-meta, add a half dose during the splash racking, and see if fermentation is affected. Add another half dose a day or 2 later.


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## sjjan (Oct 30, 2022)

One batch is fermenting on “natural” yeast which could also mean that it picked up on one of the commercial yeasts “hanging” in the cellar. The almost completed batch is on commercial yeast. Thanks  again. By the way, Reduless is available over here in Europe.


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## Rice_Guy (Oct 30, 2022)

I second the note from @winemaker81 ,,,,,,, *H**2**S needs to be dealt with immediately*.

I would rack to any available container as blue 55 gallon drums. Cooling the winery may give you more fermentation time if work pulls you away again.


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