Flavor and aroma of muscadine wines during fermentation and aging

The objectives of this study were to monitor the changes in the aroma components and descriptive sensory attributes of 'Carlos' (bronze-skinned muscadine grape) and 'Noble' (black-skinned) muscadine wines during fermentation and aging. Chemical composition and appearance of juices and wines were examined in various stages of fermentation in terms of pH, titratable acidity, level of alcohol and Hunter color. Volatile compounds were isolated from the juices and wines by continuous liquid-liquid solvent extraction and then analyzed by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry (G-CO). Twenty-six aroma-active compounds were detected by GCO. Among these were the character-impact components 2,5-Dimethyl-4-hydroxy-3(2H)-furanone (Furaneol) and 2-phenylethanol, which imparted burnt sugar-like and floral aroma notes. Other components included 2,3-butanedione, 2,3-pentanedione, ethyl butanoate, hexanal, 3-methyl-1-butanol, ethyl hexanoate, 1-octene-3-one, 3-(methylthio)propanal, ethyl hexanoate, (E,Z)-2,6-nondienal, phenethylacetate, (E)-geraniol, p-vinylguaiacol, and o-aminoacetophenone. Among the aroma compounds, 3-methyl-1-butanol was in highest concentration in both 'Carlos' and 'Noble' wines.; The aroma and taste properties of 'Carlos' and 'Noble' juices and wines were studied using descriptive analysis techniques. Multivariate statistical techniques were used to compare the sensory data with chemical data for selected aroma-active compounds. Results of principal component analysis showed that the intensity of sensory attributes and the chemical components increased after fermentation of 'Carlos' juice and then decreased in the wine during aging. For the 'Noble' juices and wines, there was an overall increase in sensory impression and chemical components after fermentation and these continued to increase during aging. Factor analysis of data for 'Carlos' and 'Noble' juices and wines revealed that when the product flavor was dominated by the positively loaded factors (e.g. ethanol aroma and taste and the bitter, astringent and sour tastes), the negatively loaded factors (e.g. sweet taste) were low or absent.