Designation of various substances that promote yeast propagation during the fermentation of the must. The yeasts need potassium, sulphur, nitrogen and phosphorus, among other things, for propagation (sprouting). These nutrients are normally present in the must. A lack of nitrogen in particular can inhibit the formation of yeast cells or in extreme cases even lead to fermentation arrest (stuck fermentation). For this reason, various nutrients are often added, especially in the case of rotten or botrytised grapes or in the production of fruit brandies. Such yeast nutrient salts are for example ammonium sulphate, diammonium phosphate and thiamine(vitamin B1). Some of these may also be added together. Within the EU, the maximum permissible amount of thiamine is 0.6 mg/l, of ammonium sulphate and/or diammonium phosphate 0.3 g/l. In the fermentation of low-nutrient and highly clarified musts, the addition has a positive effect on the fermentation process and the aroma. Yeast barks are also used as a supplement.