Effects Of Degree Of Milling On Nutritional Quality And Eating Quality Of Rice

Brown rice are rich in nutrients.Consumption of brown rice can reduce oxidative damage and incidences of chronic diseases.The degree of milling(DOM)is a critical parameter affecting the quality of rice.At present,studies on antioxidant and antiproliferative activities of phenolics in rice are all carried out experiments after extracting ingredients from raw materials.However,rice needs to be cooked and eaten.From the view of physiology,it is necessary to consider the effect of digestion on phenolics and the synergistic effect between phenolics and other nutrients in digestive juices.It can make the research more practical and the quality of rice is evaluated comprehensively.In this paper,Jinyuan 89 was used as the raw material.Rice with different DOMs were treated with milling process combined with emery roller and iron roller.Firstly,the effects of DOM on physicochemical property,nutrient component,antioxidant capacity and eating quality of rice were studied.Then,the changes of phenolics release and antioxidant capacity of rice with different DOMs during in vitro digestion were further studied.Finally,HT-29 cells were treated with digested samples collected from rice with different DOMs to investigate the effects on cell proliferation,cell cycle and apoptosis.The main conclusions are as follows:(1)Effect of DOM on physicochemical property of rice with different DOMs.Overall,as the DOM increased from 0%to 15.83%,the peak viscosity,trough viscosity,breakdown and L^*of rice showed an upward trend,while the enthalpy of gelatinization(?H),a^*,b^*,the storage modulus(G')and loss modulus(G")showed a downward trend.(2)Effect of DOM on nutrient component and antioxidant capacity.DOM was negatively correlated with moisture,fat,protein and ash content of rice,but positively correlated with amylose content.As the DOM increased from 0%to 15.83%,the contents of?-aminobutyric acid,phytic acid,total phenolic,total flavonoid,DPPH and ABTS free radicals scavenging capacities of rice decreased by 77.7%,85.4%,64.4%,84.3%,78.7%and 61.8%,respectively.The proportion of free fraction in total phenolics increased.The contents of seven phenolic acids decreased with increasing DOM.The loss of iso-ferulic acid content was the most in all phenolic acids.(3)Effect of DOM on eating quality.As the DOM increased,water absorption rate,volume expansion rate,p H and solids soup of rice showed an upward trend as a whole.Hardness,chewiness and cohesion of rice decreased and elasticity increased.As the DOM from 12.31%to 15.83%,there were no significant differences in all indicators of edible quality.(4)The changes of phenolic release and antioxidant capacity of rice with different DOMs during in vitro digestion.The in vitro digestion significantly promoted the release of phenolics and improved antioxidant capacity of rice with different DOMs.The maximum release amount of phenolics occurred at the intestinal digestion phase.ABTS free radical scavenging capacity mainly increased in small intestine digestion stage,while DPPH free radical scavenging capacity mainly increased in oral digestion stage.Total phenolic and total flavonoid content in rice had highly significant positive correlation with DPPH and ABTS free radical scavenging capacities during in vitro digestion.Compared with the control groups without enzyme,the total phenolic content,total flavonoid content,DPPH and ABTS free radical scavenging capacities significantly increased in most digested samples.After in vitro digestion,as the DOM increased from 0%to 15.83%,the total phenolic content,total flavonoid content,DPPH and ABTS free radical scavenging capacities of rice decreased by 26.8%,68.5%,48.8%and 29.9%,respectively.The contents of phenolic acids decreased with increasing DOM.The loss of sinapic acid content was the most in all phenolic acids.Furthermore,the increase of phenolic content and antioxidant capacity of rice with high DOM value was larger than that of rice with low DOM value after in vitro digestion.(5)The antiproliferative effect of digested samples collected from rice with different DOMs on HT-29 cells.The inhibition rate of HT-29 cells treated by 7.5%(v/v)digested sample of brown rice for 48 hours was 13.69%.Digested samples of other DOM rice did not inhibit the proliferation of HT-29 cells.Compared with the blank group,the cell cycle of HT-29 cells treated with digested samples of rice with different DOMs did not change significantly.The apoptosis rate of blank group was 2.05%.As the DOM increased,the apoptosis rates of HT-29cells treated with digested samples were 2.78%,2.19%,2.12%,1.85%and 1.92%,respectively.There was no significant difference in the apoptosis rate between blank group and the group of digested samples.