Study On Ultrasonic Preparation Technology And Functional Properties Of Quercetin Loaded By Casein Phosphopeptide-chitosan Self-assembly

With the increasing emphasis on nutrition and health,application of bioactive components in the field of functional foods has gradually become a research hotspot.Bioactive components such as flavones represented by quercetin,polyphenol,essential oils,carotenoids and phytosterols possess disadvantages of low water solubility,vulnerable structure,poor stability and low bioavailability.Taking advantage of food borne biomacromolecules,constructing stable and effective nano delivery vehicles for entrapment and protection of bioactives to improve their bioavailability is of great significance in the field of food nutrition.Currently,protein-based biomacromolecules(proteins or macromolecular polypeptides obtained by enzymatic hydrolysis)-polysaccharide self-assembled composite nanoparticles have been applied for the entrapment and protection of bioactive components.Ultrasound can promote the crosslinking of protein-based biomacromolecules and polysaccharides,so as to improve the loading efficiency of bioactive components and obtain nanoparticles with better functional properties.In this paper,casein phosphopeptide(CPP)-chitosan(CS)self-assembly was used to construct the embedding carrier of hydrophobic bioactive substance-quercetin(Qu),the advanced multi-mode ultrasonic technology was introduced into the preparation process of CPP-CS-Qu nanoparticles.The formulation and ultrasonic process conditions of CPP-CS-Qu nanoparticles were optimized while the structure,morphology and functional properties of quercetin composite nanoparticles prepared under different conditions were studied.Main conclusions are as follows:(1)The optimal formulation conditions for preparation of CPP-CS-Qu nanoparticles were obtained through single factor test optimization:CPP concentration of 1.5 mg/m L,CPP-CS mass ratio of 1:1,and Qu-CPP mass ratio of1:15.It was found that the embedding effect of CPP-CS composite was better than that of single CPP embedding Qu.On this basis,the optimal ultrasonic processing conditions were obtained by single factor test and orthogonal test:frequency of20/35/50 k Hz,power of 240 W,time of 20 min,and intermittent ratio of 20 s/5 s.Compared with the non-ultrasonic treatment,the embedding rate and loading rate of Qu were increased by 9.49%and 0.32%respectively,while the particle size was reduced by 119.11 nm,and the solubility of Qu in water increased from 30.98 to35.50?g/m L.After ultrasonic treatment of the formulation condition with poor embedding effect(Qu-CPP mass ratio of 1:5),the embedding rate and loading rate of Qu were significantly increased by 27.84%and 2.79%,the solubility of Qu in water increased by 39.31?g/m L.In addition,the PDI of CPP-CS-Qu(US)nanoparticle dispersion prepared by ultrasonic treatment was decreased,and the Zeta potential was increased.(2)The apparent morphology and structure of quercetin composite nanoparticles prepared under different conditions were characterized.The results showed that the addition of CS and Qu could change the polar microenvironment around the tryptophan residue in CPP and lead to fluorescence quenching.CPP was combined with CS and Qu through non-covalent interaction forces(mainly including electrostatic interaction,hydrogen bond and hydrophobic interaction).The?-helix content of CPP in CPP-CS-Qu nanoparticles increased by 3.75%and the?-sheet content decreased by 3.55%,Qu was embedded and distributed in the nanoparticles in an amorphous state.Compared with the nanoparticles prepared by embedding Qu in a single CPP,the composite of CPP and CS had better thermal stability.The surface of CPP-CS-Qu(US)nanoparticles prepared by ultrasonic treatment was smoother,with reduced average size and better dispersibility than that without ultrasonic treatment.The fluorescence intensity was further quenched by ultrasound treatment,and more groups were exposed due to the structural expansion of the polypeptide molecule,thus the interaction with CS and Qu molecules were enhanced.The thermal stability of the composite nanoparticles prepared by the ultrasonic treatment was enhanced,but the crystal structure was hardly altered.(3)The stability,antioxidant and gastrointestinal digestion properties of quercetin composite nanoparticles prepared under different conditions were studied.The results showed that compared with CPP-Qu and CPP-CS-Qu nanoparticles,the CPP-CS-Qu(US)nanoparticles prepared by ultrasonic treatment had better stability in the p H 3?6 due to the strong electrostatic interaction between CPP and CS,and the particle size was relatively small and remained stable in the range of Na Cl concentration less than 100 m M.The stability of the nanoparticles prepared by ultrasonic treatment under different heat treatment temperature,illumination duration and storage duration was improved to different degrees.The antioxidant properties of quercetin composite nanoparticles prepared under different conditions were mainly attributed to Qu molecules.In contrast with Free-Qu and CPP-Qu nanoparticles,the antioxidant property of CPP-CS-Qu system nanoparticles was significantly improved.Compared with the non-ultrasonic treatment,the DPPH and ABTS radical scavenging activities of CPP-CS-Qu(US)nanoparticles were respectively increased by 4.55%and4.78%,and the reducing ability to Fe³⁺was enhanced.Self-assembly of CPP-CS induced by ultrasound was used as the carrier for embedding Qu,which made Qu could be protected and released slowly in gastrointestinal digestive juice,thereby the bioavailability of the Qu was improved.