Influence of different doses of yeast nutrient salts on white wines from South Tyrol; Influence on sensory characteristics and aroma substances

Influence of different doses of yeast nutrient salts on white wines from South Tyrol; Influence on sensory characteristics and aroma substances. Yeast assimilable nitrogen present in the must during fermentation plays not only a particular role for the fermentation performanece, but is also always associated with the occurrence of certain aromas 177 wine. A sufficient amount of assimilable nitrogen results in fresher and more fruity wines, whereas off-flavours are often found when assimilable nitrogen is in short supply In 2005, the interaction between assimilable nitrogen and the aromatic characteristics of wine was investigated using two South Tyrolean musts ('Chardonnay' and 'Kerner') fermented with two different selected dry yeast preparations (Fermrcru VR5 and Uvaferm BC). In addition to an untreated control variant two variants with yeast nutrient salts (addition of ammonium salts: 30 g/hl and 100 g/hl, resp.) were tested The fermentation experiments were carried out in 28 liter glass carboys. Diammonium bydrogenpbospbate and ammonium sulfate were applied one half each as nutrient salts Variants with Fermicru VR5 did not ferment through, so they could not be evaluated sensorilly, but aroma analyses were performed with all variants. The data obtained were finally evaluated variance analytically. With respect to sensory characteristics the addition of nutrient salts bad no effect with the variety 'Kerner, whereas in 'Chardonnay' flavour intensity, typicity, olfactory diversity and cleanliness of aroma were rated better. With respect to aromas formed during fermentation a decrease in low-boiling sulphur-containing compounds could be analytically detected only with the variety 'Kerner' for the components of hydrogen sulphide, thioacetic acid methyl ester and dimethyl sulphide. The increased formation Of some esters and the simultaneous decrease of higher alcohols as a result of the addition of nutrient salts could be detected in both tested varieties,