GC–MS and UHPLC-based metabolomic insights into volatile and non-volatile changes in pomegranate wine during fermentation and short-term storage

Abstract

The physicochemical properties, polyphenolic composition and flavour profile of pomegranate wine produced using indigenous fruit yeast ( Hanseniaspora occidentalis ) were investigated after fermentation and short-term (10 d) storage. Colour intensity decreased by 6.6%, from 7.89 in fresh juice to 7.37 after fermentation, with no further significant change during storage. Alcohol content reached 8.72% (v/v) after fermentation and remained stable thereafter. Hydrolysable tannins, including punicalin, punicalagin and pedunculagin, increased significantly after storage, with punicalin, punicalagin and pedunculagin rising by 641.18%, 55.11% and 56.12% respectively, likely due to β-glucosidase activity from Hanseniaspora occidentalis . Gallic acid increased by 294.3% after storage and this was attributed to ellagitannin hydrolysis. Partial least square discriminant analysis (PLS-DA) revealed distinct metabolite clustering at each fermentation stage, with specific metabolites present in fresh juice and enriched in fermented and stored wine, respectively. Flavour changes were most pronounced after initial fermentation, with minimal changes after storage. Fermentation significantly modified the volatile profile, with total esters increasing 42.6-fold (0.19–8.09) and higher alcohols increasing 50.6-fold (0.98–49.62), contributing to enhanced aromatic complexity of the wine. This is the first study to monitor volatile and non-volatile compound changes after storage of pomegranate wine fermented with Hanseniaspora occidentalis , and these findings offer new insights towards optimization of and retention of wine functional properties and quality control.