Improvement of polysaccharide extraction from white grape pomace by-products using green thermal techniques

Management of winery by-products is a key challenge, and recovering bioactive compounds such as polysaccharides (PS) from grape by-products represents a sustainable alternative. Green techniques such as accelerated solvent extraction and microwave assisted extraction, and a conventional heat extraction method were studied to improve the extraction of PS from white grape pomace by-products. The PS extracts obtained were characterized in terms of molecular weight distribution, monosaccharide composition, total proteins, total polyphenols, monomeric phenolic compounds and ATR-FTIR analysis. The results showed that temperature and technique were the main factors influencing the characteristics and composition of the extracts. Lower temperatures produced extracts rich in oligosaccharides, while higher temperatures promoted the extraction of non-pectic polysaccharides, mainly related with cellulose, with a high molecular weight. Microwave assisted extraction and conventional thermal extraction improved polysaccharide extraction from grape pomace by-products, increasing yield and purity while reducing extraction time. ATR-FTIR analysis revealed a low degree of esterification in all extracts, indicating the prevalence of polar PS. This study demonstrates that emerging green techniques can be used to recover structurally different PS extracts from grape by-products. It also highlights the importance of temperature in extraction conditions, and its potential relevance for future applications in the food industry.