FAQ - What are nutrients?

[Grayson_Stewart]

I started writing up some of the FAQ's anyone want to add or change anything on this one concerning yeast nutrients?

What are yeast nutrients?
In fermentations, yeast growth must take place before the anaerobic (alcohol) fermentation can begin. In most wine applications, the common active dried yeast inoculation (when yeast is poured into the must) rate is 5 grams (0.2 ounces) per 20 liters (5 gallons) which results in an initial cell concentration of three to four million viable yeast cells per milliliter of must. Under normal conditions, the cell population will increase to 100 to 150 million viable yeast cells per milliliter before growth stops and alcohol fermentation takes over (stationary phase).

Because of this significant increase in biomass, adding Fermaid to the juice or must ensures that a proper balance of nutrients are available to the yeast during this critical growth phase. Without proper nutrition, the risk of sluggish or stuck fermentations increases. These sluggish fermentations are microbiologically unstable and can lead to the growth of undesirable organisms that can result in unwanted by-products, such as acetic acid, acetaldehyde and diacetyl.
Yeast nutrients are added at the rate of 3 grams per liter of wash (eg 60 g for 20 L). It is typically made of the following, and/or similar:

* Di-Ammonium Phosphate - Source of yeast assimilable nitrogen. Its need is well documented. About 350mg/L of Nitrogen recommended for fermenting this much sugar.
* Magnesium Sulphate - Epsom Salts. Source of Magnesium for yeast and plants alike.
* yeast hulls (deceased,but imparts vitamins and minerals) prevents stuck fermentations.
* folic acid -
* niacin
* calcium pantothenate, and
* thiamine hydrochloride.

Fermaid K - General yeast nutrient, produced by Lallemand. Do a web search if you want to know what is in it.

It is far better to use the prepackaged nutrient mixes, as these specifically target the needs of the yeast, based on quite a bit of laboratory testing & research. If these cannot be obtained then simply using 6 ounces of tomato paste will do in a pinch.