Effects Of Rice Protein On In Vitro Digestibility And Antioxidation

Rice protein is a kind of high quality plant protein,its antioxidant,anti-obesity,hypolipidemic and other physiological functions are mainly affected and restricted by the extraction process and protein composition.However,there still lacks of studies focused on the effects of different extraction methods and different components of rice protein on the antioxidant capacities of rice protein in vitro at present.So,in view of this situation,this article analyzed and measured the in vitro digestibility and antioxidant performance of proteins which included the alkaline extracted rice protein（RPA）,enzymatic extracted rice protein（RPE）,glutelin（RPG）and prolamin（RPP）by means of the experimental model of pepsin digestion for 0.5-2.0h and pancreatin digestion for 0.5-3.0h.Particularly,the indexes of evaluation of antioxidant performance included the radicals scavenging capacity(ABTS、DPPH、O₂^?-、H₂O₂),the metal ions chelating capacity(Fe²⁺、Cu²⁺),and the reducing power.Our results suggested that different extraction methods produced different digestibility of rice protein,that is to say RPA produced a high level of digestibility compared with RPE.Meanwhile,there was also significant difference in the digestive property of the main storage proteins of rice protein,namely RPG > RPP.Additionally,our results also demonstrated different extraction methods affected the in vitro antioxidant properties of rice protein.After digestion with pepsin and pancreatin,the ABTS and DPPH radicals scavenging activity exhibited by RPA-S were much stronger than those of RPE-S（P < 0.05）,and RPA showed the better radical scavenging activity than RPE,but not significantly different（P > 0.05）,Additionally,the order of metal ions(Fe²⁺ and Cu²⁺)chelating activity was RPE > RPA > RPA-S > RPE-S and RPE was significantly different from RPA,RPAS and RPE-S（P < 0.05）.Meanwhile,the order of reducing power was RPE > RPA > RPA-S > RPE-S,and RPE showed the best reducing power（P < 0.05）.After digestion with pepsin and pancreatin,RPG and RPP performed different in vitro antioxidant properties.The results showed the distribution of scavenging ABTS radicals was RPG > RP > RPP with significant differences between each other（P < 0.05）.The distribution of scavenging superoxide radicals was RP>RPG>RPP with significant difference between RPG and RPP（P < 0.05）.The H₂O₂ scavenging activity exhibited by RPG was significantly stronger than RPP（P < 0.05）.The distribution of scavenging NO was RPG > RP > RPP with significant differences between each other（P < 0.05）.The properties of chelating metal ions(Fe²⁺ and Cu²⁺)exhibited by RPG were significantly stronger than RPP（P < 0.05）.Meanwhile,the distribution of reducing power was RPG > RP > RPP with significant differences between each other（P < 0.05）.In all,our results suggested the extraction process and protein composition were the important factors that restricted and affected the in vitro digestibility and antioxidant performance of rice protein.