Antiviral and technological properties of 13-glucan-rich aqueous fractions from Pleurotus ostreatus waste biomass

In the present work, aqueous fractions were extracted from the discarded Pleurotus ostreatus biomass (AF) and from a waste product (RAF) generated from it in the industry (stipes) with the aim of valorizing these wastes into new food ingredients. Compositional, structural and functional analysis, before and after a purification step (p) to enrich its content in 13-glucans, was carried out. Moreover, the rheological properties and the nanostructure of hydrogels obtained from the 13-glucan extracts were analyzed. The unpurified fractions stood out for their significantly higher antioxidant capacity (AF, 138.55 +/- 1.20 and RAF, 118.31 +/- 1.20). As a result of the ethanolic purification process, purified samples had lower protein, ash, polyphenols and a-glucans content than the unpurified ones. Furthermore, extracts from stipes had a greater structural complexity, with more branched 13-glucans than their counterparts obtained from the whole biomass, which had a positive impact on the antiviral activity against murine norovirus. Interestingly, purified samples formed stronger hydrogels but the gelation mechanism depended on its composition and structure. AFp was able to form a gelling network with a more tightly packed structure, ascribed to the presence of less branched 13-glucans, showing the highest hardness value (2.87 +/- 0.27 N). Unpurified RAF fraction showed hydrogels with greater cohesiveness and chewiness values (4.74 +/- 0.55 N and 9.08 +/- 0.87 N, respectively). In contrast, the presence of small side chains in RAFp could also act as reinforcement agents in hydrogels formed by means of intermolecular associations, with the additional advantages of having greater antiviral activity and coming from agroindustrial residues (stipes).