Need advice on N. First time wine from fresh juice.

[SouthPhillyBr3w3r]

I am making wine for the first time. My HBC had a bulk buy of fresh Italian wine juice, so I got 6 gallons of Sangiovese. I built my starter, took my readings, and pitched the yeast. The sugar content is 23° brix, and I am using RC-212 Bourgovin yeast. I am curious about nutrients.

I read some research that suggests the addition of DAP during the innoculation and early growth phases of fermentation is not a good idea, as the inorganic ammonia compounds will actually inhibit the absorption of organic alpha-amino acids by the yeast cells, therefore reducing the effective level of YAN. I am unable to get a YAN level for my juice, but I know that with RC-212 at 23 brix, the required amount of N will be about 324.5 ppm.

I am curious whether I should boil some bread yeast and add to my fermenter, to give a source of organic amino acids as well as some b-vitamins, or if I should just wait until my Brix has dropped by 1/3, sniff for any hydrogen sulfide aroma, and add DAP as necessary at that point. In case you are curious, the study I discussed above states that once alcohol levels begin to climb, the absorption of organic amino acids is inhibited, and the yeast become dependent on inorganic sources of nitrogen such as ammonia. Therefore, organic nitrogen sources should be used initially, and inorganic sources of nitrogen are needed later in fermentation.

I have a little background in microbiology and biochemistry, so I am prone to overthinking these things. In the interest of not turning my wine into a failed science experiment, I would appreciate some input as to whether I should tinker, or if I should just leave well enough alone. Thank you.

 

[RPh_Guy]

I'm not really an expert on this, but here are some thoughts...

The "early growth phase" should be done by about 12-48 hours, right?

From what I understand, toward the end of fermentation it becomes risky to add DAP because the yeast have trouble absorbing it once the alcohol reaches a certain limit, and it leaves off-flavors when it's not utilized.

The general method suggested by the prominent labs is to add nutrients in 2 equal doses: one dose when visible fermentation has begun (around 24 hours after pitch) and one dose at 1/3 sugar depletion (5-7 days?).

I personally would suggest adding organic nutrients equal to one-half the total YAN requirement. I use Fermaid O.

In that study, did they somehow measure the actual fermentation outcome like quantitative or quantitative measurement of off-flavors or some other sensory measure of a quality end product?
Nothing else matters in my opinion.

Cheers

 

[SouthPhillyBr3w3r]

In that study, did they somehow measure the actual fermentation outcome like quantitative or quantitative measurement of off-flavors or some other sensory measure of a quality end product?
Nothing else matters in my opinion.

Cheers

They did qualitative and quantitative analysis of Hydrogen Sulfide levels in the finished product, using trained tasters (blind tasting) and a mass spectrometer.

 

[SouthPhillyBr3w3r]

So a little update. I pitched the yeast the night before yesterday. By yesterday evening, it was bubbling slowly, so I added 11g DAP(aq) to 6 gallons of wine. By the time I went to bed, the bubbles had increased in rate. When I woke up this morning and went downstairs to check, I was hit with the overwhelming scent of yeast. I turned the lights on and to my horror, found grape juice splattering from the airlock like a shower head. In all I probably only lost a quart, but it was certainly a mess to clean up. I swapped my airlock for a sanitized blow-off tube, and by now, it has calmed enough (with a few drops of fermcap) to be switched back to an airlock.

With beer, I have guidelines for blow off usage that help avoid this mess, but I am unused to Brix, so I didn't realize exactly how much sugar was there. Now that I think about it, it's about the same as a stiff barleywine, which would get a blow-off and fermcap FOR SURE!!!! I won't be making that mistake again!

 

[Maylar]

I read some research that suggests the addition of DAP during the innoculation and early growth phases of fermentation is not a good idea, as the inorganic ammonia compounds will actually inhibit the absorption of organic alpha-amino acids by the yeast cells, therefore reducing the effective level of YAN.

Unless I'm misunderstanding you, that's pretty much the opposite from what's being tossed around in the mead community. From what I've read, yeast are unable to assimilate inorganic nitrogen after about 9% ABV, so DAP is being replaced by Fermaid-O (organic) in the later stages of SNA. DAP has also fallen out of favor because it causes temperature spikes. The latest protocols are using Fermaid-K (which does contain DAP) after the lag phase and Fermaid-O after that.

 

[RPh_Guy]

Brix and Plato are roughly the same and multiply those by 4 to get a rough number of gravity points.

 

[SouthPhillyBr3w3r]

Unless I'm misunderstanding you, that's pretty much the opposite from what's being tossed around in the mead community. From what I've read, yeast are unable to assimilate inorganic nitrogen after about 9% ABV, so DAP is being replaced by Fermaid-O (organic) in the later stages of SNA. DAP has also fallen out of favor because it causes temperature spikes. The latest protocols are using Fermaid-K (which does contain DAP) after the lag phase and Fermaid-O after that.

I'm human, so it is entirely possible I misread, but I am pretty sure that is what they said. I'll reread the article and post a link.

 

[SouthPhillyBr3w3r]

This is one article I read. I cannot find the other study that I looked at.

https://psuwineandgrapes.wordpress....-fermentation-right-nutrient-supplementation/

 

[Maylar]

This is one article I read. I cannot find the other study that I looked at.

https://psuwineandgrapes.wordpress....-fermentation-right-nutrient-supplementation/

That's consistent with what I've seen elsewhere. The warning is to not use DAP during rehydration, use only GoFerm or similar. Once the ferment is underway (after the lag phase), nutrients with DAP are OK, but toward the latter part of the ferment (like the 2/3 sugar break) if ABV is more than 9% you should only use organic nitrogen. Otherwise whatever nutrient you use will not be assimilated, and it'll be left behind in your wine (yuck).