I've been reading that yeasts like nitrogen from different sources during different phases in the early stages of fermentation.
I've seen recommendations for using DAP at the end of the lag phase and Fermaid-K at the 1/3 sugar depletion phase. Does this play a bigger role than supplementing YANC and FAN already present in the must to ensure optimal fermentation dynamics?
I generally work in ten to twenty gallon batches, what is the proper dosing of DAP to use when preparing the must for introduction of the yeast, and at the end of the lag phase?
I wish that there was a universal protocol for the addition of nutrients to all fermentations, but there isn't.
There are too many caveats:
1. Wild yeast spoilage organisms are the main problem that must be addressed. They can consume many times their requirement of minerals and vitamins during the early hours of the fermentation leaving the must deficient for the added yeast when they get through their lag phase an into their growth phase. So it is not wise to add a well balanced nutrient such as Fermaid K at the beginning of fermentation when there is the potential for the presents of wild spoilage organisms such as you may find in fresh crushed apples for cider and whole berries, fresh or frozen juice.
With good cleaning and sanitary practices, there is very little problems of spoilage yeast with honey and concentrates. So, it is safe to add the well balanced nutrient at the beginning of the fermentation when the yeast needs all the nutrients and will not have to share them with spoilage organisms. Then add DAP in increments during the growth phase and into the beginning of the stationary phase. Yeast like a fresh source of nitrogen during the growth phase and will reward you with minimum production of H2S and a healthy cell through out the entire fermentation.
2. How much nutrient to add is the next problem to be addressed. For all practical purposes, honey, apple juice, corn and cane syrup contain no nutrients for the yeast. So, 2 pounds of a well balanced nutrient such as Fermaid K and 2 pounds of Fermaid 2133 (autolysis yeast) and 4 pounds of DAP / 1000 gallons of must. Grape juice concentrate contain very little nutrients for the yeast.
A lot of the nitrogen and minerals and vitamins have been removed during the preparation for evaporation. So for insurance, it is best to assume that there are little to no nutrients available for the yeast and follow the above recommendations. FAN or YAN in fresh grape juice can vary over a wide range depending on the grape varietal, vineyard practices and season from 40 PPM YAN to well over 500 PPM YAN.
If you have the YAN analysis, these are our recommendations: http://www.lallemandwine.us/products/nutrient_strains.php If you do not have a YAN analysis you should add 2 - 4 lbs. of DAP over the first 1/3 of the fermentation and 1 - 2 lbs of Fermaid K after 1/3 of the sugar has been converted to alcohol.
3. Oxygen should be considered as a yeast nutrient, so make sure that the yeast gets enough O2 near the end of its growth phase.
4. Potassium is a nutrient requirement that should be taken into consideration in honey, corn and cane sugar and grape concentrate fermentation. 1/2 to 1 lb of potassium carbonate should take care of this requirement added with in the first 12 hours of the fermentation.