Influence of must nitrogen composition on wine and spirit quality and relation with aromatic composition and defects - A review

Abstract

The development of wine-growing practices (reducing of nitrogen supply, grass cover) in order to improve the production control and environment protection lead to nitrogen deficiencies in must. Many fermentation problems appeared : stuck and sluggish fermentation, aromatic deviation. In opposite, it was underscored that must with high nitrogen content could lead to wine containing potentially dangerous molecules for human health, like amine and ethyl carbamate. Many studies related the nitrogen fertilisation and grass cover effects on vine and must composition, but just a few works were done about their consequences on wine and spirit quality. The quantitative aspects of alcoholic fermentation are now well know as the yeast nitrogen requirements (140 à 160 mg/l N). But yeast has also qualitative requirement (amino acids, vitamins, fatty acids), in relation with the medium (t°, O2, turbidity). In case of nutrient lack, even slight, yeast produce volatile acidity, H2S and many sulphur compounds (origin of aromatic defects), and fermentation rate is slowed, sometime stopped. The yeast strains play an important role because of genetic differences and specific nutrient requirements. On the other hand, the possibility of enhancing wine aroma appears with the control of the nitrogen content of must which induce mainly ester and higher alcohols formation. Furthermore, it must keep in mind that large amount of must nitrogen (> 1,000 mg/l) could also lead to problems with wine composition. Sensory analyses show correlations between must nitrogen content and soil management with wine quality. It seems that must with medium nitrogen give the better wines. The aim of this study was to resume the actual experimental knowledge on this subject.