Effect Of Traditional Processing On Bioavailability And Antioxidant Activity Of Selenoprotein In Selenium-enriched Brown Rice

Selenium-enriched germinated brown rice is not only rich in nutrients such as?-aminobutyric acid and selenium,but also has nutritional and health functions such as anti-oxidation and anti-cancer.Its protein has higher biological value and digestibility.Therefore,it is more and more popular.Cooking is the most common processing methods for brown rice,but most of the current research on selenium-enriched brown rice has focused on the raw material,and the effect of traditional processing methods on its nutritional content is rarely studied.In this study,germinated brown rice and selenium-enriched germinated brown rice were used as raw materials to explore the effect of traditional processing on the antioxidant stability of protein.In addition,the thermal processing was further studied to research the effects of cooking(normal pressure,microwave and high pressure)on protein amino acid composition,protein digestibility and bioavailability of selenium.Finally,the effects of various cooking methods on in vitro antioxidant activity of protein were investigated,and establish red blood cell oxidative damage model for further analysis.The main results of this study are as follows:(1)The antioxidant stability of protein was evaluated by measuring the ABTS·~+scavenging ability and reducing ability.The results showed that under all treatment conditions,the antioxidant activity of selenium-enriched germinated brown rice protein was higher than that of germinated brown rice.Brown rice protein could retain more than 70%of the antioxidant activity under different conditions except citric acid treatment.Heating could increase the antioxidant activity of proteins.The addition of citric acid,metal ions and salt ions significantly reduces the antioxidant activity of proteins,especially high concentrations of citric acid would lead to complete loss of protein antioxidant activity.The scavenging ability of ABTS·~+was relatively stable,but the reducing ability was significantly reduced under the conditions of light and sterilization.(2)The effects of different cooking methods(normal pressure,microwave and high pressure cooking)on the bioavailability of selenium and protein were studied.The study found that different cooking methods have no significant effects on the amino acid composition,protein and selenium content.However,the bioavailability of selenium and protein decreased significantly(p<0.05).High pressure and microwave cooking weakened the hydrophobic interactions of proteins,which led to the exposure of hydrophobic groups,as well as aggregates and precipitates of protein.Therefore,protein digestibility was decreased.Moreover,the formation of disulfide bonds will also reduce its digestibility.The results of SDS-PAGE showed that the 13 k Da prolamin is an indigestible protein,but after high pressure cooking,the 13 k Da prolamin band of non-reducing electrophoresis disappeared.It indicated that the disulfide bond formed during high pressure cooking would reduce the solubility of the prolamin,and then causes a decline in digestibility.(3)For protein,brown rice and protein digestion products,the antioxidant activity of the selenium-enriched protein is higher than germinated brown rice.Cooking has light effect on the protein's ABTS·~+scavenging rate and iron chelating ability.However,the reducing power of unselenium-enriched brown rice protein was reduced.Microwave and normal pressure cooking increased the reducing power of selenium-enriched brown rice protein.Cooking will affect the ABTS·~+scavenging ability of brown rice and protein digestion products,but the maximum reduction is 7.22%.After cooking,brown rice and selenium-enriched brown rice could maintain 65%and more than 75%of ABTS·~+scavenging ability,respectively.Except gastrointestinal digestion product of selenium-rich brown rice is lower than than gastric digestion,the rest are gastric products with a high scavenging rate.The reduction ability of brown rice and protein digestion products before and after cooking has no significant effects.The reduction ability of trypsin digestion inhibition reduction ability.The reduction ability of gastric digestion products is higher than that of gastrointestinal digestion.The scavenging capacity of hydroxyl free radicals are after cooking Except for digestion products of brown rice protein.Free radical scavenging rate of the digestive products of brown rice is higher than that of the stomach,while protein digestion product showed that stomach are higher than the gastrointestinal.(4)The effect of the digested products of brown rice protein before and after cooking on the oxidative damage of red blood cells induced by hydrogen peroxide was researched.The results showed that cooking improve the protection of red blood cells from oxidative damage.The order of protection is:the protection of high pressure treatment>the protection of microwave treatment>the protection of normal pressure treatment.The protective mechanism of the sample against oxidative damage to red blood cells is that when cells are subjected to oxidative stress,they respond to the body's oxidative stress response by regulating the expression of HRPRP,Band3 protein and Nrf2,which reducing lipid peroxidation of cell membranes and increasing enzymes activity of SOD and CAT.The production of oxidation products(LPO and MDA)is reduced.Which is protecte cells from oxidative damage,maintain the integrity of cell membranes cell morphology,and reduce the rate of hemolysis.