Published : 26-02-2020
The importance of yeast nutrients
If you have been making wine or distilling you have probably heard about yeast nutrients. A lot of research has been done on the effect of nutrient additions to fermenting mashes, in which it has been made clear that proper yeast nutrient management improves the yeast performance, vitality and viability during fermentation.
What is nutrients and why it is important?
Yeast nutrients have three important functions
1. Provide the necessary molecules and energy needed for population growth (to produce even more yeast cells).
2. Provide the building blocks for compounds produced by yeast during fermentation
- This includes ethanol, flavour and aroma compounds and many other fermentation related compounds.
3. To maintain yeast cell health
- Provide all the necessary molecules to ensure each yeast cell is functioning optimally.
The four main nutrient categories
The primary carbon source for yeast is sugar such as glucose and fructose. The breakdown of these sugars provides both a source of cellular energy as well as the starting material for the synthesis of other cellular constituents. Carbon is the backbone of organic molecules that make up living organisms.
Nitrogen is the most important nutrient after sugar. There are many sources of nitrogen which include Amino Acids, Ammonia (NH3) and Ammonium (NH4). Nitrogen deficiencies will initially lead to a sluggish fermentation, and if no nitrogen is added it will turn into a stuck fermentation. Nutrients deficiencies can easily be recognised by its characteristic smell of rotten eggs, also known as hydrogen sulphite (H2S).
The amount of nitrogen present in your must can be determined by testing the YAN (yeast assimilable nitrogen) value. Keep in mind that is test is done by a laboratory since it requires special equipment.
YAN (yeast assimilable nitrogen) is the number of different forms of nitrogen present in your fermentation mash that can be utilised by yeast. This includes amino acids, ammonia (NH3) and ammonium (NH4). Winemakers need to assess the YAN value of their fermentation mash in order to detect nutrient deficiencies early to make the correct nutrient additions.
Minerals are needed in much lower quantities compared to that of carbon (sugar) and nitrogen. Yet without these, some metabolic processes cannot occur, and some product won’t be able to be produced since it will be lacking the building blocks. These minerals include Phosphorous, Sulphur (produces fruity aromas associated with tropical fruit), Potassium, Manganese, Magnesium, Copper and Zinc.
Just like humans, yeast cannot produce their own vitamins, and should thus be taken up from the environment. Vitamins are little helpers in certain processes during yeast metabolism and aids in yeast cell protection. Without vitamins, these processes might not occur at all.
Biotin (vitamin B7) is important for yeast growth, without it, new yeast cells cannot be made. Thiamine (vitamin B1), has shown to support the protection of yeast cells against oxidative, osmotic and thermal stresses.
Keep in mind:
Fermentations consisting out of fruit and grains are rich in nutrients such as vitamins, minerals and carbon, but wine fermentations will need to be supplemented with nitrogen. Grain fermentations can be supplemented with a small amount of additional nitrogen but is not necessary. Fermentations such as sugar washes and molasses contains very little or even no micronutrients compared to that of fruit and grain fermentations and should thus be supplemented with nutrients comprising of more than just nitrogen.
The most common compounds found in yeast nutrients mixes
Every yeast nutrient composition from different suppliers are different, but they mostly a blend of the following:
Di-ammonium phosphate (DAP)
DAP is a form of inorganic nitrogen is widely used to supplement nitrogen-deficient musts. It also provides a good amount of phosphate which is an important mineral.
Yeast with low YAN values will be supplemented with DAP since it provides a good amount of nitrogen.
Yeast hulls are dead, inactive yeast cells. These yeast cells cannot ferment, instead, they act as a nutrient source for living yeast cells. They provide large amounts of important proteins, amino acids and vitamin B, which necessary for new cell production. Yeast Hulls does not contain a lot of nitrogen, that is why DAP and yeast hulls are added together.
Vitamins and minerals
As mentioned earlier, vitamins and minerals are important for certain biological reactions to take place during fermentation. Vitamins such as Biotin and Thiamine and Minerals such as Magnesium and Zinc will typically be found in a blend of yeast nutrients.
There are a number of different yeast nutrients on the market from different brands which can make it a bit difficult to know when and which to add. At Distillique, we sell three different types of nutrients which include yeast activator, DAP (Diammonium phosphate), yeast nutrients.
Yeast Activator serves as a protectant for yeast during rehydration. It is a special blend to obtain high levels of certain essential vitamins and amino acids required for healthy yeast fermentations. Yeast are most sensitive during the initial stages of re-hydration as discussed in one of our previous articles: “Active Dried Yeast: Re-hydration or direct addition?”. Infusing yeast with these essential nutrients arms them against ethanol toxicity and optimizes nutrient availability to the rehydrating yeast culture.
Keep in mind that yeast activator cannot be replaced by yeast nutrients during re-hydration. DAP, present in most nutrient mixes are excluded in yeast activator since it is harmful to rehydrating yeast. Adding nutrients containing DAP to rehydrating yeast can be more harmful than not using yeast activator.
Dosage: Use in equal quantities as yeast (for every one gram of yeast, use 1 gram of yeast activator).
Di-ammonium phosphate (DAP)
DAP can be used for fruit wines in which micronutrients such as vitamins and minerals are freely available, but nitrogen is scarce.
Dosage: Roughly 1 gram per 5 L of fermentation mash
Our yeast nutrients is a mixture of DAP, Yeast Hulls, Vitamins and Minerals, ensuring that all the nutritional needs of yeast are met.
Sugar washes, fruit mashes and molasses: Use in equal quantities as yeast (for every one gram of yeast, use 1 gram of yeast nutrients).
Grain fermentations: for every one gram of yeast, use 1/3 gram of yeast nutrients.