Comparison of inorganic and organic nitrogen supplementation of grape juice - Effect on volatile composition and aroma profile of a Chardonnay wine fermented with Saccharomyces cerevisiae yeast.

Inorganic nitrogen salts, and to a growing extent organic nitrogen preparations, are widely used to ameliorate a nitrogen deficiency in wine fermentation, but the impact of nitrogen supplementation on perceived wine sensory profile is essentially unknown. Supplementation of a low nitrogen Chardonnay grape juice with either ammonium nitrogen or combined amino acid and ammonium nitrogen showed that the type of nitrogen and concentration in the range 160-480mgN/l had a substantial impact on the formation of yeast volatile compounds and perceived wine aroma. Addition of amino acid and ammonium nitrogen increased both acetate and medium chain fatty acid esters to a greater extent and decreased higher alcohols to a lesser extent than ammonium nitrogen alone whereas ammonium nitrogen substantially increased ethyl acetate and acetic acid. Low nitrogen wines were rated relatively low in floral/fruity aroma descriptors, while moderate nitrogen wines showed a good balance between desirable and less desirable attributes, whereas high nitrogen produced either an acetic/solvent character or highest ratings for floral/fruity attributes, depending on nitrogen type. These results show that amount and type of nitrogen supplement can substantially modulate Chardonnay wine volatiles composition and perceived aroma.

Content of biogenic amines in a Chardonnay wine obtained through spontaneous and inoculated fermentations.

This paper describes the content of biogenic amines in wines obtained from a Chardonnay must inoculated with different strains of Saccharomyces cerevisiae and in a wine fermented with the indigenous yeasts (control wine). The concentrations of nonvolatile amines and phenethylamine in the wines from the inoculated must were superior to those of the control wine. This was probably due to the fact that consumption of the precursor amino acids of these amines, during fermentation, was also greater in the inoculated samples than in the control sample. Furthermore, from the results obtained it may be said that, at least to some extent, the nonvolatile amines were formed by yeasts during fermentation. The concentrations of dimethylamine, ethylamine, and pyrrolidine (volatile amines) were different for the different wines, although they did not reach concentrations sufficiently high to have any effect on the aroma.