White Labs WLN1000 Yeast Nutrient is used to increase the health of yeast by improving the fermentation and re-pitching performance. Yeats nutrient contains diammonium phosphate, essential vitamins and co-factors, nitrogen (amino acids, proteins, and peptides) and minerals. If grist is not 100% malt, then yeast nutrient can help make up for lack of nutrients. Nutrient can also be an effective boost for first and/or late generation yeast slurry. This nutrient should be added during the last 10 minutes of the boil.