Yeast Assimilable Nitrogen Source and Fermentation Temperature Affects the Chemistry and Sensory Properties of Cool Climate Riesling

Yeast-Assimilable Nitrogen (YAN) supplementation is common during commercial winemaking as it helps avoid stuck or sluggish fermentations and can improve wine quality. The majority of commercially available YAN supplementation products consist of inorganic nitrogen in the form of Diammonium Phosphate (DAP). Recent work has shown that the addition of organic nitrogen sources, such as autolyzed yeast nutrient or mixed amino acids, can confer additional benefits in terms of fermentation kinetics and volatile profiles. Further, fermentation temperature and nitrogen metabolism appear to have an interactive effect, meaning that nutrient packages may have varying outcomes at different fermentation temperatures. This work sought to add to the understanding of the impacts of nitrogen source and supplementation level by comparing the chemistry and sensory properties of wines supplemented with a range of inorganic versus organic nitrogen sources and at two different supplementation rates. Wine sensory attributes were assessed by a panel using a projective mapping technique known as Napping®. Wines that received the lower supplementation rate across several treatments were associated with more desirable sensory attributes. A subsequent experiment examined the impact of fermentation temperature on the chemical and sensory outcomes of Riesling using inorganic or organic nitrogen sources at three different fermentation temperatures. Fermentation temperature had a strong effect on fermentation kinetics, with warmer fermentation temperatures yielding faster fermentation. These wines were also evaluated by Napping®, and wines fermented at the lowest temperature were associated with more desirable sensory attributes