The impact of branched chain and aromatic amino acids on fermentation kinetics and aroma biosynthesis by wine yeast Saccharomyces cerevisiae
Abstract
One of the major determinants of wine quality is the aroma. Wine aroma is the human perception of the matrix of grape and yeast derived volatiles and their interaction that contribute to flavour wine. Most common are higher alcohols, ester and aldehydes. In previous studies the formation of characteristic volatile compounds have been linked to the metabolism of branched-chain and aromatic amino acids
(BCAAs) in synthetic grape must. Here we report on an investigation to assess the impact of the initial amino acid concentration on the production of aroma compounds by the industrial yeast VIN13 grown in both synthetic and real grape musts. Fermentations were conducted using real must were conducted in 4L and 80L volume and only 80 mL volumes were used for the synthetic grape. Either valine, phenylalanine, leucine or isoleucine were used as the yeast amino acids nitrogen source at a rate of in addition to dibasic ammonium sulphate to make a total YAN of 300mg/L. The rate of fermentation was determined by measuring weight loss (representative of CO2 release) in time-course experiments. All experiments were fermented to dryness. The analysis of major volatiles was carried out by gas chromatography coupled with a flame ionizing detector (GC-FID). To characterise the relationship between amino acid used as sole nitrogen sources and the resultant aroma profile, multivariate analysis were conducted and one-way ANOVA was used to compare differences of individual compound accumulation between treatments. A linear correlation was found between the initial concentration of the BCAAs and their related aroma compounds in both synthetic and real grape musts for all volumes. Molar concentrations of fusel alcohols and fusel acids can be reasonably predicted from the initial molar concentration of BCAAs even when the synthetic must is supplied with a more complex amino acid mixture. Nonetheless predictability was reduced complex cocktail of amino acids was used as nitrogen source. Real must fermentation confirmed the association between amino and aroma composition and manipulation of must amino acid composition can be a valuable tool for wine-makers and other food processors.
Issue: Macrowine 2016
Type: Article
Authors
*IWBT-Stellenbosch University