Characterization of Phenolic Compounds and Other Compositions of Red Grape Pomace Extracts after Solid-State Fermentation with Aspergillus spp.

Abstract

Grape pomace is solid byproduct of wine processing and a valuable resource for sustainable valorization. This study aimed to evaluate the solid-state fermentation of grape pomace from two cultivars (Mourvèdre and Shiraz) with two Aspergillus strains for up to 6 days to produce valuable substances. The fermentation process was monitored by weight change and pH. The aqueous extracts were characterized by titratable acidity, organic acids, total soluble contents, individual sugars, total phenolic content, and individual phenolics. Fermentation significantly increased pH with decreased titratable acidity and organic acid content. Total soluble solids were decreased with the decrease of individual sugar content. Fermentation did not increase the total phenolic content but significantly increased selected extractable phenolics, as gallic acid increased by 76–196% for both cultivars, and p-coumaric acid increased by 713–963% for Shiraz pomace. The increased phenolic content in this proof-of-concept study demonstrated the potential of grape pomace valorization to produce valuable compounds.