Nutritional Property Of Soybean Lipid-lowering Component And Its Potential To Deliver Flavonoid As A Carrier

Low denatured soy flakes,a byproduct of soybean oil extraction,rich in lipid-lowering components(i.e.,soy protein,oligosaccharide and soluble polysaccharide)is an excellent raw material for preparing plant-based healthy foods.However,the conventional extraction methods for preparation of soy protein,oligosaccharide and soluble polysaccharide are mainly based on multi-stage and multi-step strategy,focused on unitary component,involved addition and remove of some reagents leading to the inefficient,time-consuming and complicated extraction process with a few co-extraction and full-utilization strategy.Additionally,soy whey protein with high contents of anti-nutritional components results in the difficulty for full utilization by conventional technologies.Moreover,effects of soybean oligosaccharide and soluble polysaccharide on nutritional and functional properties of soy protein are still unknown.Therefore,the present study aims to optimize excellent strategies for co-extraction of soy lipid-lowering components with high efficiency by new technologies,to explain the effects of soybean oligosaccharide and soluble polysaccharide on nutritional and functional properties of soy protein.Furthermore,the feasibility of soy lipid-lowering components for delivery flavonoid was discussed to expand its application range.The present study provides new ideas for the design and preparation of plant-based healthy food ingredients.The main findings are listed as follows:(1)Sixteen kinds of soy lipid-lowering components(SE)were prepared by high pressure homogenization,high temperature,plant hydrolase and alcalase hydrolysis treatments.The functional properties,activities of anti-nutritional components,lipid-lowering activity in vitro and protein and soluble saccharide yields of SE were comprehensively evaluated.Spearman correlation analysis was carried to identify the key lipid-lowering activity component of SE.The results showed that SE mainly composed of protein(>46.7%),contained polysaccharide(10.4-27.8%)and oligosaccharide(12.5-17.6%).SE prepared by conventional method possessed normal extraction yields of protein and soluble saccharide and high contents of soybean agglutinin and trypsin inhibitor with good functional properties and high lipid-lowering activity in vitro.SE prepared by high-pressure homogenization treatment possessed high extraction rates of protein and soluble saccharide and relative high contents of soybean agglutinin and trypsin inhibitor with normal functional properties and lipid-lowering activity in vitro.SE prepared by high temperature treatment exhibited high extraction rates of protein and soluble saccharide and low contents of soybean agglutinin and trypsin inhibitor with good functional properties and normal lipid-lowering activity.SE prepared by plant hydrolase treatment showed normal extraction yields of protein and soluble saccharide and low content of soybean agglutinin and high content of trypsin inhibitor with good functional properties and high lipid-lowering activity in vitro.SE prepared by alcalase hydrolysis treatment showed highest soluble polysaccharide extraction yield and high contents of soybean agglutinin and trypsin inhibitor with good functional properties and poor lipid-lowering activity in vitro.Therefore,high temperature treatment and plant hydrolase treatment are co-extraction strategies to prepare SE with good functional and nutritional properties.Additionally,Correlation analysis indicated that the anti-digestive protein fragments in SE played key roles in its pancreatic lipase inhibitory activity and cholesterol micelle solubility inhibitory activity.(2)The peptide composition and metabolites profile of three types of SE were analyzed after simulated gastrointestinal digestion in vitro and colon fermentation based on UPLC-MS/MS technology to verify the nutritional properties of SE.The results showed that SE prepared by high temperature treatment preferred to release peptides with molecular weight less than 500 Da during gastrointestinal digestion.While soy protein isolate(SPI),SE prepared by conventional technology and pectinase treatment were more likely to release peptides with molecular weight ranged from 700 to 2700 Da.During colon fermentation,SE released more bioactive peptides(ACE and DPP-IV inhibitor)than SPI.Oligosaccharide and polysaccharide in SE promoted the release of organic acids,accelerated tryptophan metabolism and linoleic acid metabolism to produce indole acrylic acid,indole lactic acid and linoleic acid which had positive effects on reducing intestinal permeability,regulating mucosal homeostasis,improving intestinal barrier integrity.Oligosaccharide and polysaccharide in SE inhibited the production of secondary bile acids and protein spoilage products i.e.amines effectively improving the nutritional quality of soy protein.(3)Parameters for preparation of SE-galangin delivery system by pH-driven were optimized.Loading capacity of three types of SE-galangin delivery system were evaluated.Stability of SE-galangin delivery system was evaluated under simulated food processing and storage conditions.Effect of SE delivery system on improving bioavailability of galangin was evaluated by simulated gastrointestinal digestion in vitro.Finally,the underlying mechanism of construction for SE-galangin delivery system by pH-driven method was cleared by Fourier transform infrared spectroscopy,X-ray crystal diffraction spectroscopy and transmission electron microscopy.The results showed that the optimal conditions for preparation of SE-galangin delivery system were SE concentration at 40 mg/m L,galangin: SE at 1%,and 5min for compounding.SE-galangin delivery system showed good stability during storage,thermal treatment,sodium ions treatment and redispersibility with higher bioavailability(240%)of galangin than that of free galangin.Potential mechanism for construction SE-galangin by pH-driven method might be related to the decomposed and unfolded protein subunit which led to the decreased content of β-sheets and increased content of random coil with more released hydrophobic sites under extreme alkaline environment.Then dissolved galangin bound to the hydrophobic groups of protein through hydrophobic interaction in amorphous form,and then the protein subunits refolded and re-aggregated when the pH returns to neutrality to form new nano-scale spherical particles.Compared with SPI,the nanoparticles formed by SE and galangin showed smaller size(<100 nm),especially nanoparticles formed by SE(prepared by high temperature and pectinase treatments)and galangin showed smaller size and better uniformity than that of SE(prepared by conventional technology)and galangin.