Identification of characteristic volatile compounds and prediction of fermentation degree of pomelo wine using partial least squares regression

The aim of this study was to evaluate the characteristic volatile organic compounds (VOCs) profile of pomelo wine and determine an index for predicting fermentation degree of pomelo wine. Fermentation conditions of pomelo fruit were: initial sugar content, 20 degrees Brix; pH 4.0; yeast inoculum size, 2 g of inoculum in 10000 g of fermentation medium; fermentation temperature, 28 degrees C; total fermentation time, 285 h. Changes in VOCs content in pomelo wine fermented for different periods were analyzed by gas chromatography-mass spectrometry. In total, 105 VOCs were identified in pomelo wine throughout the fermentation process, which included 31 alkenes, 19 esters, 20 alcohols, 11 aldehydes or ketones, 9 aromatics, 6 alkanes, 5 acids, and 4 other volatile compounds. Differences in VOCs contents in pomelo wine at different fermentation stages were analyzed by principal component analysis, cluster analysis, and partial least squares regression (PLS). PLS models revealed that the ratio of alpha-phellandrene/geraniol in pomelo wine could be as the potential index for determining the fermentation degree of pomelo wine. This study provides evidence for improving the quality of pomelo wine for industrial production.