| As one of the most important food crops in the world,rice provides the main energy and nutrition for human body.The main components of rice are starch?80%?90%?and protein?7%?8%?.Compared with other cereal proteins,protein has the characteristics of low sensitivity,high biological value and comprehensive nutritional value.As a storage protein in grains,rice protein has poor functional characteristics,which limits its application in food industry.Therefore,it is very important to modify rice protein by chemical modification,especially by glycosylation.Because of the long time and uncontrollable process of glycosylation,it is easy to produce harmful end products of advanced glycosylation,so it is very important to control the process of glycosylation by choosing the type and quantity of sugar and the method of modification.Therefore,in this paper,rice protein was selected as raw material,Wet Heat?WH?and Hydrothermal?HT?combined with high static pressure treatment to carry out glycosylation reaction between rice protein and different sugar components,and its physical and chemical properties,functional properties and antioxidant activity of products were studied preliminarily,in order to provide theoretical basis and technical basis for the processing and production of functional rice glycoprotein,and expand The industrial application value of rice protein.The specific conclusions are as follows:?1?The grafting degree and solubility of rice protein and different sugars?glucose,xylose,xylan?were studied by the methods of hydrothermal?WH?and hydrothermal?HT?glycosylation.It was found that the grafting degree and solubility of rice protein and xylose increased the most,when the reaction time was 20 minutes,the p H value was 8,and the mass ratio of xylose to rice protein was 7:1,the grafting degree and solubility of rice protein increased the most With the increase of reaction time,p H value and the ratio of sugar to protein,the browning degree increased.In the analysis of the physicochemical properties of the six glycosylated products,it was found that the product?RP-XH?of rice protein glycosylated with xylose under hydrothermal condition had the most obvious change in physicochemical properties,with the highest content of total and free sulfhydryl groups,9.80?mol/g protein and 6.55?mol/g protein,respectively,and the lowest content of disulfide bond was 0.91?mol/g protein and SDS-PAGE showed that the six glycosylated products all formed different degree aggregates,among which RP-XH aggregates were the most.The results showed that the six glycosylated products were all in a more hydrophilic microenvironment,the UV absorption was enhanced,the?maxred shift of RP-XH was the most,the UV absorption was the strongest,the surface hydrophobicity was the lowest 168.48,the content of?-helix and?-corner in the secondary structure of the protein decreased most significantly,and the main amino acid involved in the reaction was arginine.The results showed that the solubility of rice protein modified by glycosylation was improved,and the solubility and grafting degree were closely related to the structure and physicochemical properties of the product.The emulsifying and foaming properties of the products were determined.It was found that the functional properties of the products were improved significantly.When the p H was between 6 and 8,the emulsifying activity of RP-XH was increased significantly,and the change of the functional properties was related to the surface hydrophobicity.Because RP-XH has the highest grafting degree,solubility and the most obvious changes in physical and chemical properties,it is proposed to use high hydrostatic pressure composite hydrothermal for further study.?2?The physicochemical and functional properties of four products?RP-X,100?400 MPa?produced by the glycosylation of rice protein with xylose and its blank control were studied by the method of high hydrostatic pressure?100?400 MPa?combined with hydrothermal method.It was found that the grafting degree of 300 MPa RP-X reached the maximum of 62.56%,and the solubility was 33.12%.The browning degree increased with the increase of each index.The free sulfhydryl and total sulfhydryl contents of the four products were significantly increased,among which the free sulfhydryl content of 300mpa RP-X was the highest,and the surface hydrophobicity was the lowest?58.92?.The UV absorption intensity increased obviously,the red shift of?maxin the fluorescence spectrum was up to 363 nm,the irregular curl of the secondary structure of 300 MPa RP-X was up to 56.42%,the second was that 200 MPa RP-X was up to 8.68%,its?-fold was up to 29.56%,and the?-helix structure of the two products was the least.It can be seen from the analysis that the solubility and grafting degree of the product are related to the physical and chemical properties.In terms of functional properties,200 MPa RP-X has the highest emulsifying activity and foaming ability.From the analysis,it can be seen that the functional properties are related to the surface hydrophobicity.?3?The antioxidant activities of the glycosylation products of glucose,xylose,xylan and rice protein were studied under hydrothermal,hydrothermal and high hydrostatic pressure.The products formed with xylan have the strongest ABTS+·scavenging ability under humid and hydrothermal conditions;the DPPH·scavenging ability,OH·scavenging ability and O2-·scavenging ability of the products under high hydrostatic pressure combined with hydrothermal treatment are the strongest,followed by the hydrothermal glycosylation products and the hydrothermal glycosylation products;among all the reaction products,the products formed with protein and xylose have the strongest antioxidant ability,followed by It is xylan and glucose,and rice protein and xylose have outstanding superoxide anion free radical scavenging ability in 300 MPa high hydrostatic pressure treatment.According to the comprehensive data,the antioxidant activity of the reaction product with xylose and xylan is much higher than that of glucose.The results showed that glycosylation could improve the antioxidation of rice protein,and the methods and kinds of glycosylation had influence on the antioxidation of rice protein. |
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