Study On The Effect Of Pretreatment And Cooking Methods On The Quality And Storage Characteristics Of Red Rice

Red rice is a kind of specific rice resource with red seed coat,and its seed coat is rich in active ingredients such as proanthocyanidins.The active ingredients in red rice are mainly distributed in the outer rice bran layer,but it contains more cellulose,which affects the taste of red rice and hinders the inner starch gelatinization.In order to better utilize red rice resources,the paper takes red rice as the research object,and first explores the effects of three pretreatment methods(microwave,steaming,and boiling)on the quality of red rice.Then the influence of microwave pretreatment process on the cooking quality and physical and chemical properties of red rice is explored.Following that,the differences in the physical and chemical properties of unpretreated red rice(URR)and pretreated red rice(PRR)after cooking are explored.Finally,the impact of storage time on quality,cooking characteristics and nutritional characteristics of different packaged PRRs.First,the effects of three commonly used coarse grains pretreatment methods were explored on the cooking performance and proanthocyanidins of red rice under the same processing time.When the time is 360 s: boiling shortens the cooking time of red rice by48.66%,but the retention rate of proanthocyanidins is only 14.55%,which is a great loss;microwaving and steaming effectively reduce the cooking time of red rice(55.37% And27.85%),and has a higher retention rate of proanthocyanidins(57.27% and 53.20%).Therefore,microwaving is selected for the pretreatment of red rice.Secondly,the influence of microwave pretreatment process on the cooking quality and physical and chemical properties of red rice was investigated.The optimal process conditions were as follows: 66 g of red rice was soaked in distilled water,3 times the quality of the red rice,at 50°C for 30 minutes,and then treated with a microwave dose of 12 W/g for 90 s 4times after being drained(for each microwave interval,soaked in water at 18-23°C for 10 s,microwave processing it after drained;the interval between two microwave processing was about 30 s;the average temperature before microwave processing was 25.47±3.73?,and the average temperature after microwave processing was 94.47±3.65?).With the increase of the number of microwaves,the gelatinization characteristics and swelling force of PRR decreased,and the crystallinity of starch decreased from 17.85% to 2.75%;the content of polyphenols and flavonoids decreased,with final retention rates respectively 56.25% and 67.45%,whose retention rate is relatively high.Then,the influence of cooking methods on physical and chemical properties of URR and PRR was explored.After Atmospheric pressure boiling(APB),Pressure boiling(PB)and Atmospheric pressure steaming(APS)treatments,the final starch hydrolysis degree of PRR is respectively 4.03%,14.44% and 7.77% higher than that of URR;the relative crystallinity of PRR is respectively 1.28%,1.18% and 0.72% lower than that of URR;and the hardness of PRR is respectively 14.65%,9.68% and 19.35% lower than that of URR.At the same time,the experiment found out that the swelling force,proanthocyanidin content and antioxidant activity of PRR also decreased.In terms of product chroma,the red-green value a* of the PRR after cooking is reduced,which means the red color faded;while the light-dark value L*after cooking increases,which means the color of red rice became brighter.Finally,the influence of storage time on PRR quality factors,cooking performance and nutritional characteristics was explored.The results showed that: when stored for 6 m,the fatty acid value of vacuum packaged PRR was 29.71 mg Na OH/100 g DW,and there was no odor,while that of the normal pressure packaged PRR was 36.25 mg Na OH/100 g DW,with a slight odor.With the increase of storage time,the water absorption rate,optimal cooking time,gelatinization degree and crude protein content of PRR remained basically unchanged,while the content of fat,polyphenols,proanthocyanidins and flavonoids decreased,but remained at a high level.PRR can still be cooked with white rice after storage to achieve complementary nutrition.