| Functional dairy products are an emerging industry.By adding active physiologicals,dairy ptoducts can not only enrich nutrition,but also have good flavor.Common functional dairy products,such as milk tea,coffee with milk,fruit milk and other dairy products,contain a large number of natura polyphenols.The effect of these natural polyphenols on milk protein in cow's milk is the focus of recent research.The interaction mechanism between bovine proteins ?-casein(?-CN),?-lactoglobulin(?-LG)and theaflavin(TA),chlorogenic acid(CA)and delphinidin-3-O-glucoside(D3G)was investigated by ultraviolet(UV)-visible absorption spectroscopy,multi-fluorescence spectrophotometry,Dynamic light scattering(DLS)measurements,multi-fluorescence spectrophotometry,circular dichroism(CD)spectrometry and fourier transform infrared(FTIR)spectrometry.Whether these polyphenols interact with the bovine milk proteins and how they affect the structure of the proteins should be validated;secondly,the interactions of three common dietary polyphenols with ?-LG and reduction of their allergenic capacity were studied;finally,the effects of the TA,CA and D3 G on the functionality of ?-LG were also investigated.The main research contents and results of this artile are as follows:1.The structural classification and physioogical functions of polyphenols were described;the structural and function of proteins were also described;the mechanism of interaction between polyphenols and milk protein was studied in detail;the research progress of poyphenos and proteins,as well as the significance,research content and innovation of this article were described.2.The interaction mechanism between bovine proteins ?-CN,?-LG and TA,CA)and D3 G was investigated by ultraviolet(UV)-visible absorption spectroscopy,multi-fluorescence spectrophotometry,Dynamic light scattering(DLS)measurements,multi-fluorescence spectrophotometry,circular dichroism(CD)spectrometry and fourier transform infrared(FTIR)spectrometry.Whether these polyphenols interact with the bovine milk proteins and how they affect the structure of the proteins should be validated.Multi-spectral results showed that TA,CA and D3 G caused the fluorescence quenching of ?-CN and ?-LG to form complex,so the mechanism of fluorescence quenching was mainly static quenching.TA,CA and D3 G could bind with ?-CN and the quenching ability on the intrinsic fluorescence intensity value of ?-CN was TA > D3 G > CA.TA,CA and D3 G could bind with ?-LG and the quenching ability on the intrinsic fluorescence intensity value of ?-LG was TA > CA > D3 G.The hydrophobic forces played a major role in the interactions of TA,CA and D3 G with ?-CN and ?-LG.Ultraviolet(UV)-visible absorption spectroscopy,multi-fluorescence spectrophotometry,Dynamic light scattering(DLS)measurements and synchronous fluorescence spectra showed that TA,CA and D3 G interacted with ?-CN and ?-LG to form complexes,affecting the microenvironment of amino acid residues,causing the primary structure of protein changed.According to the results of fluorescence EEM spectroscopy,TA,CA and D3 G not only affect the primary structure of ?-CN and ?-LG,but also caused changes in their secondary structure.According to the results of fourier transform infrared(FTIR)spectrometry,TA,CA and D3 G had an effect on the secondary structure of ?-CN and ?-LG,which can lead to the decrease of ?-sheet and the increase of ?-helix.3.The interactions of TA,CA and D3 G with ?-LG and reduction of their allergenic capacity were studied by enzyme-linked immunosorbent assay(ELISA)and molecular modeling study.The allergenic capacity of ?-LG was reduced after binding with TA,CA and D3 G,with CA exhibiting the most reduction in IgE binding than TA and D3 G.By calculating the inhibition rate,the inhibition rate of TA to ?-LG reached 70.5%,CA reached 71.7% and D3 G reached 68.0%,respectively.Their sequence was CA >TA > D3 G.Experiments on molecular modeling studies showed that TA,CA and D3 G bound to ?-LG in the hydrophobic regions.the polyphenol binding site directly obscures the IgE linear epitopes or near the epitopes,preventing IgE from approaching the ?-LG.As a results,the allergenicity decreased might be due to the partial epitopes were combined with TA,CA and D3 G.4.The effects of the TA,CA and D3 G on the functionality of ?-LG were also investigated by in vitro simulated digestion and DPPH scavenging free radicals.The in vitro simulated digestion data showed that the digestibility of the complexes of TA,CA and D3 G with ?-LG was higher than that of pure protein,indicating that the addition of TA,CA and D3 G can promote the digeastion of ?-LG.According to DPPH data,after adding TA,CA and D3 G,the DPPH clearance rate had a large increase may be due to the superposition of the antioxidant properties of complexes formed by the interaction of polyphenols with ?-LG.Therefore,the antioxidant activity of ?-LG-TA/CA/D3 G could be significantly improved. |
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