Functional and bioactive properties of the protein-polysaccharide extracts from brown algae: Exploring novel functional ingredients

The present work reports the extraction of protein-polysaccharide extracts from brown algae ( A. nodosum and S. latissima ) for potential food industry applications. A sequential extraction method was employed to maximize yields by incorporating ultrasound, pH adjustment, and enzymatic treatment. The resulting extracts were characterized by their composition, bioactive properties, and emulsifying capabilities. Although the overall extraction yield was significantly higher for A. nodosum extracts, the protein content in both species' extracts increased at least threefold following enzymatic treatment, with S. latissima achieving the highest protein percentages. The enzymatically treated extracts mainly consisted of low molecular weight proteins (17–25 %) and carbohydrates (59–62 %), with alginate and fucoidan as the primary polysaccharides. These extracts exhibited a high emulsifying capacity (approximately 99 %), attributed to their relatively high protein content (acting as surfactants) and lower molecular weight, which enhanced oil droplet stabilization in emulsions. The increased protein content positively correlated with angiotensin-converting enzyme (ACE) inhibitory activity. Furthermore, the antioxidant activity was higher in extracts from A. nodosum, which is linked to sulfated fucoidan/fucan structures and polyphenols. • Protein-polysaccharide conjugates were produced from brown algae. • The combined yield of the sequential extraction process reached up to 25.8 %. • Uronic acids represent the major polysaccharides in the extracts. • Enzymatic treatment yielded extracts with the highest emulsifying capacity and bioactivity. • The potential of the extracts as functional ingredients is promising.