Influence of Diammonium Phosphate Addition to Fermentation on Wine Biologicals

Abstract Nitrogen is a key component of grape must, which provides an essential nutrient for yeast growth that is necessary for complete alcoholic fermentation and to produce wine with desirable flavor characteristics. However, the nitrogen content of grapes is highly variable, and often limiting, and is influenced by many viticulturally related factors. Nitrogen-deficient grape must is associated with several fermentation problems. Suboptimal yeast growth can lead to prolonged fermentation kinetics and unfermented residual sugar. In addition, yeast flavor metabolism is affected, such that ester production is reduced and higher alcohols (fusel alcohols) and sulfide production is increased, leading to wines having more complex but usually less desirable sensory profiles. Inorganic nitrogen, usually in the form of diammonium phosphate (DAP), is widely used to supplement nitrogen-deficient musts. Assimilation of this species involves multiple metabolic pathways, which result in altered metabolite production. Therefore, DAP addition can dramatically modify non-volatile wine composition, such as glycerol and organic acids, as well as volatile metabolite composition, such as esters, alcohols, and volatile fatty acids and sulfur compounds. Grape products with sensory importance or healthful significance can be affected to various degrees by nitrogen status in the vineyard and in fermentation. Therefore, appropriate DAP application can improve the sensory properties, but the improvement in quality depends on several factors including yeast strain, initial must nitrogen content and extent of DAP addition.