Comparative Characterization of Aroma Compounds in Merlot Wine by LiChrolut-EN-Based Aroma Extract Dilution Analysis and Odor Activity Value

Abstract

It has been challenging to select the best method to extract and analyze aroma-active compounds in wine due to high concentration of alcohols in the sample. The objectives of this study were to investigate the applicability of a LiChrolut-EN-based solid-phase extraction (SPE) for wine aroma extraction and to characterize the aroma-active compounds in Merlot wine. Volatile compounds in a Merlot wine were extracted with Lichrolut-EN SPE or liquid-liquid extraction (LLE) followed by solvent-assisted flavor evaporation (SAFE). Both extracts were used for aroma extract dilution analysis (AEDA). Selected aroma-active compounds were further quantitated and their odor activity values (OAV) were calculated. Both SPE and LLE extracts can be used for aroma extract dilution analysis. The odorants with high flavor dilution (FD ≥ 64) values in Merlot wine were ethyl 2-methylpropanoate, ethyl butanoate, ethyl 2-methylbutanoate, ethyl 3-methylbutanoate, ethyl hexanoate, ethyl octanoate, 3-methylbutyl acetate, 2/3-methyl-1-butanol, 2-phenylethanol, acetic acid, 2-methylpropanoic acid, butanoic acid, 3-methylbutanoic acid, hexanoic acid, β-damascenone, E-whiskeylactone, γ-nonalactone, 3-(methylthio) propanol, 4-hydroxy-2,5-dimethyl-3(2H)-furanone, 2-ethyl-4-hydroxy-5-methyl-3(2H)-furanone, sotolon, vanillin, guaiacol, and eugenol. Quantitative analysis and calculated odor activity value (OAV) suggested that ethyl butanoate, ethyl 2-methylbutanoate, ethyl hexanoate, 3-methylbutyl acetate, ethyl octanoate, ethyl acetate, 2/3-methyl-1-butanol, butanoic acid, 3-methylbutanoic acid, hexanoic acid, β-damascenone, and acetaldehyde could be the major contributors (OAV ≥ 5) to Merlot wine aroma. Lichrolut-EN SPE was generally comparable with LLE to obtain wine aroma compounds. SPE extract had higher flavor dilution values for esters, and lower for acids and some alcohols than LLE, which is advantageous to study aroma-active compounds in alcoholic beverages due to less interferences from alcohol and acid and improved chromatography. This study confirmed the applicability of LiChrolut-EN SPE as an alternative extraction method for wine aroma characterization to improve laboratory efficiency and minimize the usage of organic solvent.