Effects Of Ultra-high Pressure Treatment On Structure And Function Of Buckwheat 13S Globulin

With the change of modern people's life style and the continuous improvement of living standard,increasing the proportion of soybean,buckwheat and other plant protein in diet can effectively improve the health level of human body.Buckwheat,as a unique "medicine food" homologous grain treasure in China,contains protein,starch,fat,vitamins,minerals and trace elements and other rich nutritional functional components.Its protein content is about 15%-17%(w/w).It can significantly reduce cholesterol level,inhibit fat accumulation and promote excretion.However,the traditional thermal processing may lead to the denaturation of proteins and other heat sensitive active ingredients,which affects the nutritional function of buckwheat protein.In recent years,ultra-high pressure(UHP),as a new technology of non-thermal processing,have been widely studied and has unique advantages and application prospects.A high activity buckwheat 13 S globulin was prepared by alkali extraction,DEAE-Sepharose Fast Flow ion exchange chromatography and Sephadex G-75 gel filtration chromatography respectively.The effects of UHP on the structure and functional properties of buckwheat were studied.The main conclusions are as follows:(1)BWP1,BWP2 and BWP3 were prepared from buckwheat crude protein by DEAE Sepharose Fast Flow ion exchange chromatography.Among them,BWP1,BWP2 and BWP3 had the best ability to adsorb bile acid salt in vitro and the lowest digestibility in vitro.Subsequently,the BWP3 fractions were further separated and purified by Sephadex G-75 gel filtration chromatography.The four components of BWP31,BWP32,BWP33 and BWP34 were obtained.Among them,the ability of the BWP32 component to adsorb cholate in vitro was the best and the lowest digestibility was in vitro.Finally,BWP32 was identified by twelve alkyl sulphate polyacrylamide(SDS-PAGE)gel electrophoresis,and its relative molecular weight was 38 k Da,belonging to globulin.Therefore,BWP32 was identified as a highly active buckwheat 13 s globulin(BW13SG).(2)BW13SG was treated with UHP under two different p H buffer conditions.Through the determination of carbonyl,mercapto,disulfide bond and surface hydrophobicity index,it was clarified that UHP treatment could promote the conversion between mercapto and disulfide bond of BW13 SG,and the oxidation damage of protein was less under proper pressure treatment.By means of modern analysis methods such as fluorescence spectroscopy and Fourier infrared spectroscopy,the change rule of secondary and tertiary structure of BW13 SG under different UHP treatment conditions was preliminarily verified.UHPtreatment will destroy the protein structure,and with the increase of pressure,the content of ?-helix will increase,resulting in the change of secondary structure.UHP treatment changed the microenvironment of the aromatic amino acid residues in BW13 SG,and changed the tertiary structure of the protein.(3)This paper takes UHP technology as the breakthrough point.Through the study on the functional characteristics of BW13 SG after UHP treatment,it is found that in the Gly-HCl buffer solution with p H 3.0,the solubility of BW13 SG can be increased to 91.2% by the UHP treatment of 500 MPa.In this acid buffer solution,the emulsification and emulsification stability of BW13 SG can be effectively improved by the UHP treatment.Both of them are improved with the increase of UHP treatment pressure at 500 MPa The maximum value is82.2m2/g and 41.6%.The holding time had no significant effect on foaming and foam stability of BW13 SG.In the buffer solution of p H 8.0,the foaming pressure of BW13 SG appeared at the maximum pressure of 200 MPa(91.6%),and then decreased with the increase of pressure.BW13 SG showed better foaming ability under weak alkaline conditions,but the foam showed better stability under acidic conditions.Therefore,when we modify the food,if we need to enhance the foaming property,we can choose the pressure treatment in the alkaline buffer.If we need to enhance the foam stability,we can choose the pressure treatment in acidic buffer.