Fermaid-K® is a blended complex yeast nutrient that supplies inorganic nitrogen (DAP), organic nitrogen (alpha amino), key nutrients (magnesium sulfate, thiamine, folic acid, niacin, biotin and calcium pantothenate) and yeast hulls.
It is best to add Fermaid-K® over two additions. The first addition is made at the end of the yeast lag phase (6 to 12 hours after yeast inoculation) and the second addition is made when sugar depletion is depleted by 1/3 (the end of exponential growth and the beginning of the stationary phase).
With proper rehydration and handling, the yeast cell population should be at least 4 million cells/ml at inoculation. By the time the second Fermaid-K® addition is made, this population should have grown to about 100 million cells/ml. Yeast cells are still reproducing during the stationary phase, and to do this effectively, especially in high sugar musts, they need oxygen as well as the components of Fermaid-K®, including nitrogen (for protein synthesis), sterols and fatty acids (for maintaining alcohol resistance and carrier molecule activity). In addition, the inactivated yeast cell walls in Fermaid-K® adsorb medium-chain fatty acids that are toxic to yeast, and provide nucleation sites to help keep the yeast in suspension.