Co-extraction of soy protein and polysaccharide with lipid-lowering activity: Characterization of functional property, nutritional property and colonic fermentation property through a metabolomics approach

Defatted soy meal is a candidate for preparing lipid-lowering active ingredient. The study aimed to optimally co-extract soy protein and polysaccharide with lipid-lowering activity and improved functional and nutritional properties using non-conventional extraction techniques, i.e. thermal-, high pressure homogenization- and enzyme-assisted extraction. Non-conventional extraction enhanced the yields of soy protein and soluble saccharides and inactivated anti-nutrients. Soy extract (SE) prepared by pectinase-assisted extraction possessed not only strong in vitro lipid-lowering activity (i.e. cholesterol micellar inhibition activity, bile salts binding capacity, pancreatic lipase inhibition activity and cholesterol esterase inhibition activity), but also excellent functional (i.e. instant solubility of protein, low turbidity and acceptable color) and nutritional properties (i.e. none agglutinin activity). Resistant-digested fragment of 7S/11S played key role in lipid-lowering activity of SE. Moreover, SE beneficially altered colonic fermentation property of soy protein through promoting the release of bioactive peptides and organic acids, accelerating tryptophan and linoleic acid metabolism to produce indole acrylic acid, indole lactic acid and linoleic acid, and inhibiting putrefactive compounds (i.e. piperidine and tyramine). Oligosaccharide and polysaccharide in SE improved functional and nutritional properties of soy protein without compromising its lipid-lowering activity.