Study On Improving Digestibility In Vitro Of Rice Protein By Modification

Rice protein has a reasonable components of essential amino acids and a low allergenicity. As a major source of grain protein, digestibility of rice protein is low and unsatisfactory. Using reasonable modification methods to improve its digestibility is helpful to improve their efficiency, thereby improving the nutritional status of resident. Focusing on improving rice protein digestibility, acylation, microwave or both were used in this paper. In addition, physicochemical properties were measured in order to know well about how these approaches affect digestibility in vitro.Firstly, using production of-NH2 as an index, the impact of reagent dosage, acylation time and substrate concentration on digestibility in vitro of rice protein was studied, respectively. Experimental results showed that with the increase of acetic anhydride dosage, acylation time and substrate concentration, rice protein could be hydrolyzed better by trypsin; while hydrolysis degree by pepsin appeared reducing slightly after the first increases. Using production of-NH2 as an index, the impact of microwave power, microwave time and substrate concentration on digestibility in vitro was studied. Experimental results showed that with the increase of microwave power, microwave time and substrate concentration, rice protein could be hydrolyzed better by trypsin and pepsin both.Rice protein digestibility in vitro of pepsin, trypsin and pepsin-trypsin reached maximum level in different modification conditions when modified by acylation, along with the biggest increases 4%, 12%, 8%, respectively. Also, rice protein digestibility in vitro of pepsin, trypsin and pepsin-trypsin had maximum value in different modification conditions when modified by microwave, while the largest increases were 17%, 8%, 16%, respectively. XW and WX could improve pepsin-trypsin digestibility in vitro better, increasing by 19% and 17%, respectively.Osborne was used to get albumin, globulin, prolamin and gluten of rice protein. Pepsin-trypsin digestibility in vitro of all components was measured before and after modification. The results illustrated that W, XW, WX almost had the same effect on pepsin-trypsin digestibility in vitro, increasing it about 8%, while the best method for globulin, prolamin and gluten was WX, XW, XW, increasing it by 12%, 16%, 19%, respectively.Secondly, fluorescence spectroscopy, FT-IR and other physicochemical properties of rice protein and its components were measured before and after modification in order to know that how acylation and microwave affected rice protein digestibility in vitro. Experimental showed that methods improved the solubility of rice protein, reduced the content of disulfide, reduced the content of α- helix and β- folded. Zeta potential and surface hydrophobicity were changed differently: Zeta potential and surface hydrophobicity decreased(p H 7.5) after acylation significantly; Zeta potential decreased slightly after modified by microwave while surface hydrophobicity showed an increasing trend(p H 7.5). Physicochemical properties of components exhibited different trends, having a great relationship with itselves.Finally, physicochemical properties, such as solubility, surface hydrophobicity, Zeta potential, disulfide bonds of modified rice protein, were analyzed by SPSS in order to calculate the correlationship between physicochemical properties and digestibility in vitro. The results showed that pepsin digestibility in vitro was significant correlated(P<0.05) with disulfide bonds, solubility, β- fold. Trypsin digestibility in vitro showed significant correlation(P<0.05) with disulfide bonds, solubility and Zeta potential.