Structural Characterization Of Polysaccharides From ’Pingguo’ Pear Residue And Their Interactions With Whey Protein

’Pingguo’ pear is one of the most popular pear varieties in Northeast China.Its pulp is tasty,crispy and juicy,which have a variety of nutrients,such as amino acids,flavonoids,iron,etc’Pingguo’ pear have the effects of clearing lungs,diuresis,and quenching thirst.At present,’Pingguo’ pear have produced as fruit juices,beverages and other products.A large amount of pear residue are made from the production process,which is usually used as fertilizer or discarded,resulting in waste of resources.Many studies have shown that pear residue contains polysaccharides,which polysaccharides are one of the most important biological macromolecular substances and have a variety of biological activities in organismsIn this paper,PRP were extracted by microwave-assisted enzymatic method from PRP After deproteinization and decolorization,the antioxidant activity,hypoglycemic activity,monosaccharide composition,relative molecular mass,chemical composition,surface structure,and interaction with whey protein were studied.These studies will provide a theoretical basis for further processing and utilization in the future.The results of the study were as follows:1.PRP was extracted by microwave-assisted enzymatic method,and response surface optimization test was used to determine the best extraction process for polysaccharides:the material-to-liquid ratio was 1:15 g/mL,the microwave time was 2 min,the microwave power was 560 W,and the PRP extraction rate was 47.28±0.16 mg/g2.The deproteinization and decolorization process of the crude PRP extract and its anti-oxidation and hypoglycemic activity in vitro were studied.Study the deproteinization and decolorization effect of PRP by four methods including activated carbon adsorption method,macroporous resin adsorption method,papain method and trichloroacetic acid method.The results show that the protein removal rate of HPD700 macroporous resin adsorption method was 72.34±0.32%,polysaccharides etention rate was 53.21±0.45%,the decolorization rate was 61.03±0.59%,and the comprehensive score was 63.21,the deproteinization and decolorization efficiency was the best.At 1.0 mg/mL,the hydroxyl radical scavenging rate was 76.60±0.36%,the nitrite scavenging power was 76.60±0.41%,and the peroxidation capacity of plastids was 25.61±0.55%,the inhibition rate of α-glucosidase was 18.18±0.21%,and the inhibition rate of a-amylase was 20.09±0.31%,and its antioxidant capacity was dependent on concentration3.Various technical methods were used to characterize the structure of PRP.Analysis of its chemical composition showed that its total sugar,sulfate and protein content were 59.18%,4.67%,and 1.26%,respectively.PRP contained two components with different molecular weights of 74374.15 Da and 1601.51 Da.PRP was mainly composed of rhamnose,galacturonic acid,glucose,galactose and arabinose,and according to the peak time,it can be determined that its molar ratio is 0.02:0.07:1:0.33:0.12.FT-IR showed that PRP was a pyran-type polysaccharide containing β-glycosidic bonds.Scanning electron microscopy showed that PRP was distributed in granular form,with a loose micro structure on the surface,showing a layered stack of flakes status.4.The changes in the interaction between PRP and whey protein(WP)under different pH were studied.When the pH was between 3.0-5.0,polysaccharides and proteins form electrostatic complexes through electrostatic interactions,resulting in an irease in particle size.The combination of the two makes the protein peptide chains unfold,more conjugated double bonds were exposed,and UV characteristics peak intensity increased,and the fluorescence intensity of the maximum emission wavelength gradually decreased,which affect the α-helical structure of the protein.When the pH was between 6.0-9.0,the electrostatic repulsion between the polysaccharide and the protein were increased.The particle size and absolute value of the Zeta-potential were increased,the maximum absorption peak intensity of the ultraviolet spectrum were decreased,the maximum emission wavelength blue had a change,the maximum fluorescence intensity were decreased,and changed the α-helix structure of the protein,which were attribute to termal incompatibility of the composite solution.