Effects Of Food Macromolecules On The Stability And Bioaccessibility Of Anthocyanins In Black Rice Beverage

Black rice is a valuable rice species,rich in nutrients and active ingredients such as anthocyanins.However,anthocyanins are extremely unstable due to their unique charged structure and are prone to degradation and discoloration during processing.In this paper,we investigated the effects of protein,dietary fiber and starch degradation on the stability and antioxidant activity of anthocyanin in black rice beverage during processing and storage,the effects of different food macromolecules on the stability and bioaccessibility of anthocyanin in black rice beverage during in vitro simulated digestion,and the possible mechanisms of the interaction between macromolecules and anthocyanin.The main findings are as follows The main findings are as follows:1.The effects of different food macromolecules on the stability of anthocyanin processing in black rice beverage: The black rice beverage was prepared by enzymatic degradation of protein,dietary fiber and starch in black rice,and the effects of enzymatic degradation and autoclaving on the stability of anthocyanin were investigated.The results showed that the anthocyanin was degraded to different degrees during the enzymatic digestion and sterilization process,and the retention rates of anthocyanin in black rice beverage were 38.08%-57.77% and 9.68%-16.08%in each enzymatic digestion group after enzymatic digestion and sterilization,which were lower than those of 62.88% and 17.62% in the whole grain group.The retention rates of anthocyanin in the protein,fiber and amylase groups after sterilization were14.42%,16.08% and 9.68%,respectively,indicating that starch had the strongest protective effect on anthocyanin during sterilization,followed by protein and weaker dietary fiber.Although the black rice beverages showed different degrees of degradation of anthocyanins,there was no significant difference in the antioxidant activity of black rice beverages in different groups after the same processing treatment,indicating that the degradation products of anthocyanins also had antioxidant activity.2.Effect of different food macromolecules on the storage stability of anthocyanin in black rice beverages: The effect of food macromolecules on the stability of anthocyanin was investigated by placing the black rice beverages of each group under different temperatures(4℃,37℃)and light(avoiding light and direct sunlight)for 10 d.The results showed that the anthocyanin content of all groups decreased significantly under all conditions except 4℃,and the degradation of anthocyanin was in accordance with the characteristics of the primary kinetic model,and the degradation rate of anthocyanin was the fastest under the condition of 37℃ and light avoidance.Compared with the aqueous extract of anthocyanin,the retention rate of anthocyanin was significantly increased in both the whole grain group and each enzymatic digestion group,and the retention rate of anthocyanin was the highest in the whole grain group.Although there were different degrees of degradation of anthocyanin during storage,the antioxidant activity of anthocyanin extracts of black rice beverages at the end of storage only decreased significantly at 37 ° C under light-proof conditions,which was consistent with the trend of total phenolic content,indicating that phenolics were the main antioxidant substances in black rice beverages and the antioxidant capacity of anthocyanin could be compensated by the generated phenolics.3.Effect of different food macromolecules on the bioaccessibility of anthocyanin in black rice beverage: The protective effect of food macromolecules on anthocyanin in black rice beverage was investigated through in vitro simulated oral and gastrointestinal digestion experiments.The results showed that the degradation of anthocyanin was less during oral and gastric digestion;the degradation of anthocyanin increased during intestinal digestion,and the retention rate of the extract was 40.68%,while the retention rate of anthocyanin increased significantly in the whole grain group,proteolytic group,cellulolytic group,and amylolytic group,85.55%,65.91%,69.01%,and 64.56%,respectively,at the end of digestion in the whole grain group,the bioaccessibility of anthocyanins in the proteolytic,cellulolytic,and amylolytic groups was 39.35%,37.21%,34.34%,and 37.06%,respectively.These results suggest that food macromolecules reduce the degradation of anthocyanins mainly through their interaction with anthocyanins.The digestion process was accompanied by the release of active substances,and the bioaccessibility of total phenols in the whole grain,proteolytic,cellulolytic,and amylolytic groups at the end of digestion was51.27%,52.76%,44.73%,and 45.92%,respectively,while the bioaccessibility of total flavonoids reached 50.54%,49.11%,44.66%,and 49.27%,respectively.The antioxidant activity of digesting solution also increased with the release of bioactive substances during digestion,and at the end of digestion,the strongest ABTS radical scavenging ability was in the digesting solution of the proteolytic group,and the strongest oxygen radical absorbing ability and iron ion reducing ability was in the digesting solution of the whole grain group,and the groups with stronger antioxidant activity measured by different methods were not consistent,which was due to the fact that the bioactive substances in the digesting solution of black rice beverage in each group This is due to the differences in the fractions and contents of the substances in the digest of the black rice drinks.4.Investigation of the mechanisms by which different food macromolecules affect the stability and bioaccessibility of anthocyanins: The possible mechanisms by which macromolecules affect the stability of anthocyanins were investigated by analyzing the interactions of rice starch,protein and dietary fiber with cornetin3-O-glucoside(C3G),the main anthocyanin component of black rice.The results of particle size distribution,scanning electron microscopy and X-ray diffraction analysis indicated that C3 G formed a V-type complex with rice starch,which was mainly bound to each other by hydrophobic interaction and hydrogen bonding.The results of fluorescence spectroscopy analysis and infrared analysis indicated that the rice protein and C3 G may bind to each other through electrostatic,hydrogen bonding and hydrophobic interactions.The interaction between the two was investigated by studying the environmental factors affecting the adsorption of C3 G by black rice peel dietary fiber,and the results showed that the increase of ionic strength in the solution was favorable to the adsorption of C3 G,and the increase of temperature was unfavorable to the adsorption of C3 G,and these phenomena indicated the existence of hydrogen bonding and hydrophobic interactions between the two.