Don't add any of the acid. It will probably push you over the acidity level and cause your yeast to stall, or at least get grumpy and start stinking.
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This is my approach (and although there are similarities to other nutrient methodologies, we do differ somewhat). It agrees for the most part with the recommendations of Lallemand and other commercial yeast manufacturers.
First, I make an assumption that the honey that I use in any of my musts provides negligible amounts of YAN.
Next, I determine what (if any) fruit I will use in primary fermentation.
Then, I try to find out (for melomels) how much YAN is present in the fruit I plan to use (measured in ppm, for the given volume of fruit I'll add in primary). If I can't find info on YAN for my particular fruit, I assume a baseline value of 100 ppm. That's close enough for gov't (and mead) work.
Then I work out the dilution of that fruit-supplied YAN in my total volume of must. If for example I am mixing up a 5 gallon batch of must, and one gallon is pure fruit at 100 ppm, then I will dilute by a ratio of 1/5, so the net YAN in my fully mixed must is 100 * 1/5, or 20 ppm.
I next find the nitrogen requirements of my yeast. For most commercial yeast strains we only know if the demand is low, medium or high. For low demand yeasts, I ensure that the total YAN is 225 ppm. For medium demand yeasts, I ensure that the total YAN is 300 ppm. For high demand yeasts, I ensure that the total YAN is 350 ppm. These are numbers that I've found through trial and (mostly) error that will produce clean ferments with minimal H2S production in my meads.
Note: Those values are what I use for "normal strength" meads, which for me are musts that range in initial gravity from 1.080 to 1.100 (Initial Brix range of 20 to 24). For initial Brix of 24 to 27 (SG from 1.101 to 1.115) I multiply my normal strength numbers by 1.1. For Brix from 27 to 32 (SG from 1.116 to 1.140) I multiply the normal strength numbers by 1.25. For initial gravities in excess of that, I wing it.
I calculate how much Fermaid-K and DAP to use knowing that Fermaid-K has 13% YAN by weight and DAP is 21% YAN by weight. Another way to express the YAN content of those is that 1 gram of Fermaid-K provides 130 ppm of YAN to a single liter of must, and 1 gram of DAP provides 210 ppm of YAN to a liter of must.
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08-30-2015, 08:35 PM #10 Squatchy
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How to Calculate Nutrient Additions Using Fermaid-O
The amount of required nutrient additions are based on your starting gravity. For an easier calculation convert to Brix and figure out your target mg of Nitrogen per liter using the following as a starting point:
21°Bx = 200 mg N/L
23°Bx = 250 mg N/L
25°Bx = 300 mg N/L
27°Bx = 350 mg N/L
1g/gal of Fermaid-O = 50ppm N/L (effectiveness)
(1g = roughly .25 tsp)
Example:
In a 5 gallon batch of 1.115 SG (27°Bx)
Target = 350 mg N/L
Equates to 7g/gal (350 mg / 5 gals)
35g of total Fermaid-O to be used in this 5 gallon batch
