The amino acid metabolism by Saccharomyces cerevisiae during alcoholic fermentation has relevant impact on wine aroma sensory profile. This work had as main objective the study the role of the amino acid composition on the production of a fermented wine-like solution. For this, 5 synthetic media containing different nitrogen sources were fermented by S. cerevisiae and the resulting wines were analyzed: A – ammonia; C – casein amino acids; AC – ammonia and casein; AP – ammonia and preferred amino acids (arginine, asparagine, aspartic acid, glutamine and glutamic acid); AA – ammonia and aroma precursor amino acids (isoleucine, leucine, valine, phenylalanine and tyrosine). Significant differences were found for 1-propanal, 1-butanol, 2-methyl-1-propanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-phenylethanol, isoamyl acetate and phenylethyl acetate. The sample AA had the highest values for all these compounds. PCA and clustering analysis separated sample AA from the others, in a positive correlation to the first PC. The sensory evaluation corroborates with the chemical analysis with sample A having the higher scores for aromatic intensity, fruity and floral aromas. It also had the highest value for wine-like character, although no significant difference was observed (p>0,05). Sample AP had the highest score for sulphur compounds aromas. A second experiment was conducted with samples containing ammonia and aroma precursor amino acids, in which each sample lacked one of the tested amino acids. Significant differences were found for 1-propanol, 1-butanol, 2-methyl-1-propanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-phenylethanol and phenylethyl acetate. Sample A, fermented only with ammonia as single source of nitrogen, had in general the lower concentration of these compounds. Samples deficient in phenylalanine (A and F) and isoleucine had, respectively, lower concentrations of their metabolic products, phenylethanol and phenylethyl acetate, and 2-methyl-1-butanol. This behavior was not observed for the other samples. PCA and clustering analysis showed that sample A was isolated from the others, negatively related with PC1 (41,26%) and to the chemical compounds, except for ethanal. Sensory evaluation didn‟t show substantial differences among samples, evidencing the lack of relevant influence of the absence of one aroma precursor amino acid on the wine sensory profile. The results from both experiments lead to the conclusion that the medium amino acid composition is a determinant factor affecting wine aroma.
- Mestrado em Engenharia Alimentar
Aminoacid metabolism and the production of wine aroma compounds by Saccharomyces cerevisiae
Araújo, L. D. (Student). Jun 2012
Student thesis: Master's Thesis