How different SO2 doses impact amino acid and volatile profile of white wines

Abstract

Sulphur dioxide (SO2) is a well-established preservative in the wine industry. Its ability to act in different stages of the process as an antioxidant and an antiseptic as main characteristics makes it versatile. However, the need for its reduction or even its replacement has been increasing by the regulatory authorities as well as by the final consumer. To understand the impact of SO2 during ageing on volatile organic compounds (VOCs) and amino acids (AAs) profiles, two white wines (one varietal and one blend) were aged under the same conditions, in the presence of different doses of SO2. After fermentation (t=0), 0, 30, 60, 90 and 120 mg/L of SO2 were applied, wines were kept over lees for 3 months (t=3), then were bottled after 3 (t=6) and 9 (t=12) months. VOCs were analysed by HS-SPME-GC/MS for all samples and the AAs were analyzed by HPLC-DAD for t=0 and t=3 wines. A total of 83 VOCs were tentatively identified, 70 in monovarietal wine and 73 in the blend wine. The main chemical groups present are esters, alcohols, carboxylic acids, aldehydes and 12 miscellaneous compounds. When a Principal Component Analysis (PCA) was performed on VOCs semi-quantification of each wine it was observed that the 1st and 2nd PCs explained between 64% and 76 % of the overall system variance, for monovarietal and blend wines respectively. In monovarietal wine was attained lower distinctions for different SO2 applied doses on samples with 3 and 12 months. However, for 6 months of evolution samples are well separated. In this case, both principal components seem to influence the distribution of samples with a similar weight. For the blend wine, a less clear distribution of the samples was observed for evolution time of 3 and 6 months. This may indicate that blend wine might be less sensitive to SO2 doses and evolution time when compared with Antão Vaz wines. AAs profile showed that maturation on lees lead to an increasing total concentration of AAs. Based on PCA analyses it was observed that SO2 also influences the evolution of the amino acids especially on the AV wines.