Guangfeng Wu

In this study, the effects of origin (Chinese, France, and America), intensity of toasting, and degree of charring on the volatiles of oak whisky barrels were comprehensively investigated via liquid–liquid extraction–gas chromatography–mass spectrometry (LLE–GC–MS) combined with multivariate statistical analysis. Results of principal component analysis (PCA) showed that the main oak–derived volatiles in oak were more influenced by origin and toasting than by charring. French oak had a higher content of volatile compounds than the other two origins, and this difference decreased with toasting and charring. The process of toasting and charring was important for the release of volatile compounds from oak. The content of most oak–derived volatiles increased with deeper toasting intensity, and the degree of charring promoted or inhibited the release of oak–derived volatiles. The volatile components in oak blocks were affected by the two–factor interaction of toasting and charring. Continuing the process of the charring of oak at a certain level of toasting may have an enhancing or diminishing effect on the content of different volatile compounds, depending on the circumstances.

Sensory interactions exist between 3-alkyl-2-methoxypyrazines and various volatiles in wines. In this study, the binary blending of Cabernet Franc wines containing high levels of MPs and three monovarietal red wines with two proportions was conducted after fermentation. Volatiles were detected by gas chromatography-mass spectrometry (GC-MS), and wines were evaluated by quantitative descriptive analysis at three-month intervals during six-month bottle aging. Results showed blending wines exhibited lower intensity of ‘green pepper’, especially CFC samples blended by Cabernet Sauvignon wines with an even higher concentration of 3-isobutyl-2-methoxypyrazine (IBMP). Based on Pearson correlation analysis, acetates could promote the expression of ‘tropical fruity’ and suppress ‘green pepper’ caused by IBMP. Positive correlation was observed among ‘green pepper’, ‘herbaceous’, and ‘berry’. The concentration balance between IBMP and other volatiles associated with ‘green pepper’ and fruity notes was further investigated through sensory experiments in aroma reconstitution. Higher pleasant fruity perception was obtained with the concentration proportion of 1-hexanol (1000 μg/L), isoamyl acetate (550 μg/L), ethyl hexanoate (400 μg/L), and ethyl octanoate (900 μg/L) as in CFC samples. Blending wines with proper concentration of those volatiles would be efficient to weaken ‘green pepper’ and highlight fruity notes, which provided scientific theory on sensory modification of IBMP through blending technique.