Physicochemical Properties Of Se-enriched Peanut Protein Before And After Modificatied Using High Pressure Cell Disruption

As one of the high quality plant proteins, peanut contains24%-36%protein withhigh nutritional value. Its nutritional value is as good as animal protein, rich inessential amino acids, vitamins, trace elements and minerals. Selenium is one of thetrace elements that human body need, playing an important role in biologicalfunctions after synthesizing with protein. In this text, Se-enriched arachin andSe-enriched coarachin were prepared using the method of alkali extraction and acidprecipitation. The physicochemical, structural, functional and antioxidant propertieswere investigated. However, the solubility, emulsifying properties and other propertiesof unmodified peanut protein were not ideal, limiting its application in the foodindustry. In this paper, the high-pressure cell disruption was used to modify peanutprotein with different pressures to improve the functional properties and offer atheoretical basis for industrial production applications.From the analysis of selenium content, the selenium content of Se-enrichedcoarachin and Se-enriched arachin was up to420.83μg/kg and203.10μg/kg.Amino acid analysis showed that selenium-enriched peanut protein had higher qualitythan ordinary peanut protein. The Met and Cys were detected in Se-enriched arachin,which were essential amino acids for different biological activity. The disulfide bondcontents of four peanut protein were the highest, followed by total sulfhydryl andexposed sulfhydryl sequentially. The content of disulfide,tatal sulfhydryl andexposed sulfhydryl of Se-enriched peanut protein isolates were85.53,47.65and27.32μmol/g, respectively. This indicated that protein molecules had a lot of buriedinside sulfhydryl, resulting in strong resistance in heat treatment of food processing.According to the surface of the microscopic structure of SEM, Se-enriched coarachinpresented with more massive and sheet structure, while Se-enriched arachin wasmore round with small volume spherical structure.The solubility values were lowest at about pH5.0, the maximum solubilityshowed over than pH10.0. The solubility at pH11.0of Se-enriched peanut proteinisolates, Se-enriched coarachin, Se-enriched arachin and ordinary peanut proteinisolates were35.0%,35.55%,27.97%and31.49%, respectively. The four kinds ofprotein had the similar emulsifying properties, and Se-enriched coarachin displayedthe highest foaming activity and foaming stability about119.53%and13.63%, whileSe-enriched arachin got the lowest about95.13%and9.63%, respectively. Accordingto DSC curve, compared with other types of plant protein, the thermal denaturation temperature of peanut protein was significantly higher, and its thermal stability wasrelatively stronger. Especially, the thermal stability of the Se-enriched arachin wasstronger than that of Se-enriched, with the maximum endothermic peak at157.4℃and136.5℃. The results of ultraviolet absorption characteristic curves reflecteddifferences in the residue kinds and content of four kinds peanut protein, which wascorrelated with the solubility, emulsifying and foaming properties. The antioxidantactivity of four kinds peanut protein in the three systems were different, but changingin the same trend. The Se-enriched coarachin had the strongest antioxidant activity,followed by Se-enriched peanut protein isolates, Se-enriched arachin, and ordinarypeanut protein isolates, respectively. In the system of DPPH radical inhibition, theradical scavenging activity of Se-enriched coarachin was95.88%. Static rheologicalproperties of the measurement results showed that the four kinds peanut protein werenon-Newtonian fluids. Se-enriched coarachin had the maximum viscosity, andSe-enriched arachin had the minimum.After0,7,14,20,27,34,40KPSI of high pressure cell disruption process,protein appeared new conformation with more exposed ultraviolet absorbing residues.Analysis of protein particles by electron microscopy sweep surface morphologyillustrated the generation of the chippy and rod-shaped structure. In conclusion, thesolubility of27KPSI treated peanut protein is the best and the best emulsifying abilityand emulsifying stability was obtained under14KPSI treatment, while the idealfoaming stability was got under the pressure of40KPSI.