Structure Investigation of Polysaccharides Extracted from Spent Coffee Grounds Using an Eco-Friendly Technique
Zuzana Košťáľová, Malamatenia Manavaki, Stamatia Christaki, Emmanouil‐Nikolaos Papadakis, Ioannis Mourtzinos
Abstract
Coffee is one of the most marketable products worldwide but throughout the production chain, many by-products and waste are generated, e.g., spent coffee grounds (SCG). SCG are considered a promising source of polysaccharides. In the present study, the polysaccharides from SCG were recovered through microwave-assisted extraction. Detailed structural analysis showed that SCG were mainly composed of low-branched galactomannan, followed by various lengths and branches of galactan or arabinogalactan chains whose side chains are randomly ended by glucuronic acid. These findings indicate that glucuronic acid remains attached to the arabinogalactan chain even after coffee roasting and brewing. The investigation confirmed that microwave-assisted extraction, as a green extraction technique, is a promising method for preparing polysaccharides with lower molecular weight. This extraction method ensures the recovery of SCG polysaccharides with potential biological activity without destroying the glucuronic acid at the arabinogalactan chains.