Diammonium phosphate or DAP for short is a widely used Yeast Nutrient in Brewing, Cider, Mead, Winemaking and Hard Seltzer. DAP delivers valuable nitrogen and phosphate to yeast cells. Wort is generally rich in nitrogen, but a little supplementation can help high-gravity beers complete fermentation. Phosphates also help ensure smooth fermentation of worts that contain large portions of non-malt adjuncts.
DAP (diammonium phosphate) is a major source of nitrogen for low-malt or sugar-rich mashes and washes. Recommended to add the dose in stages during the first half of fermentation. DAP stimulates fermentation rate, so if too much is added at once, the yeast may ferment too fast and too hot.
Diammonium phosphate is an inorganic source of nutrients. It provides 210 parts per million (ppm) of YAN per gram per liter of must. Thus, 1 gram (0.3 oz) of DAP in a liter (1.06 qt) of must will give you 210 ppm of YAN. Just be careful not to use too much.
Should be added at beginning of fermentation, but could be added towards the end of a slow or stuck fermentation.
This yeast nutrient is pure Diammonium Phosphate (DAP). Most fermentable sugar sources used in Cider, Perry or Mead are generally deficient in the essential nutrients for good yeast metabolism and a yeast nutrient of some sort is required. Nitrogen is one such element and DAP is a readily assimilable source.
Use at the rate of 1 gram per 5 litres of must to aid yeast and help reduce later problems with hydrogen sulfide.
The simplest way for most home winemakers to supplement nitrogen is with the granular material diammonium phosphate, also called DAP. The legal addition limit of ammonium salts like DAP for commercial wine in the US is 968 ppm, well above the levels needed to assure a healthy yeast population and successful fermentation. Peynaud recommends a range of addition is from 10 to 20 g per hectoliter of must, or about 0.4 to 0.8 g/gallon. If your must is low in YAN or your yeast is one with high-demand requirements, you should consider an addition of at least 0.5 g/gallon (0.5 g/3.8 L) and have enough DAP on hand to go as high as 2 g/gallon (2 g/3.8 L).