Preparation Of Collagen And Flavonoids From Lycium Barbarum Leaves And Its Stabilizing Effect On Lutein Emulsion

Collagen and flavonoids from Lycium barbarum leaves(LBLF)are important components in food,which play an important role in the functional characteristics and quality of food.The coexistence and interaction of LBLF and collagen is inevitable in food processing,daily diet and human digestion.Studies have shown that polyphenol compounds have unique structure and physicochemical properties,which can change the function and bioavailability of proteins in the process of interaction with proteins,including protein solubility,foaming ability,emulsifying stability and protein structure.Therefore,the combination of polyphenols and proteins is considered to be a safe and convenient strategy to effectively improve the functional properties of proteins in order to expand the application fields.This study aimed to prepare complex with the main system of LBLF and collagen,reveal its structure characterization and performance evaluation,and explore the stability of the complex on lutein emulsion.The main research contents and results are as follows:(1)Preparation of LBLF and collagen complexThe compound of LBLF and collagen was prepared by solvent removal method.LBLF quality,pH value and chloride ion concentration were selected as the main factors,with the drug loading and encapsulation rate as the response values to conduct a single factor experiment,which aims to select the optimal point of each factors.Response surface methodology was designed on the basis of single factor experiment,and the optimal preparation parameters were determined by statistical analysis of test results and response surface regression model.(2)Structural characterization and performance evaluation of the LBLF and collagen complexCombined with fourier transform infrared spectroscopy,UV-Vis absorption spectroscopy,fluorescence spectroscopy and circular dichroism spectroscopy analysis before and after the composite collagen structure change.The results showed that collagen binds to LBLF,secondary structure changes,α-helix is transformed to β-fold,structure tend to be ordered,microenvironment of amino acid residues changes,The intermolecular forces are mainly hydrogen bonding and hydrophobicity.X-ray diffraction analysis showed that the content of collagen crystal region increased and intermolecular hydrogen bond force increased after the addition of LBLF.Scanning electron microscopy(SEM)and atomic force microscopy(AFM)showed that the appearance of collagen changed when it was combined with LBLF.The changes in protein structure also lead to changes in its properties.After the addition of LBLF,the hydrophobicity of collagen decreased,antioxidant capacity increased,foaming capacity and emulsification capacity increased,and foam stability and emulsification stability also significantly increased.(3)Study on the stabilization effect of LBLF and collagen complex on lutein emulsionThe compound has good emulsifying ability,so the stability of the compound on lutein emulsion was further explored.The results showed that compared with the collagen-stabilized lutein emulsion,the complex stabilized lutein emulsion had smaller particle size,uniform distribution and larger absolute value of Zeta-potential,indicating that the emulsion had better stability.The compound can enhance the thickness of the interfacial layer of the emulsion,effectively prevent oxygen from entering the oil phase of the emulsion,inhibit the rancidity of the emulsion to a certain extent,enhance the antioxidant effect of the emulsion,and maintain the stability of the emulsion system.The apparent viscosity of complex-stabilized lutein emulsion was higher than that of collagen-stabilized lutein emulsion.When collagen interacts with LBLF,conformation changes,surface groups are exposed,surface charge increases,intermolecular repulsion increases,and the emulsion system is more stable.Therefore,complex stable lutein emulsion has better thermal stability,freeze-thaw stability and salt ion stability.Due to the high free radical scavenging ability of LBLF,the complex has a positive protective effect on lutein in the emulsion under different conditions during the storage period,and reduces the decomposition of lutein.In the process of simulating gastrointestinal digestion,the complex has high physical stability and generates steric hindrance in the emulsion,which effectively maintains the stability of the emulsion and protects the bioavailability of lutein.