Study On The Quality Control Of Whole Grain Brown Rice By Different Processing Methods

Brown rice is rich in nutrients and is an important whole grain.Brown rice has a dense layer of seed coat on its surface,and it has problems of long cooking time and poor taste when eaten in a granular manner.In order to retain the brown rice nutrition and at the same time improve its food quality to the greatest extent.In this thesis,in order to improve food quality of brown rice,the raw materials is three kinds of the milling rate of 2% of brown rice(Jingyue-1 and Suijing-18 for long grain,Longjing-31 for short round grain)and processing method is respectively low temperature plasma,superheated steam and enzymatic hydrolysis assisted pregelatinization.The improvement effect was compared with those of rice samples with different milling rate,and also studied the mechanism of improving the quality of brown rice by the three processing methods,in the hope that the three processing methods could be used to produce nutritious and convenient whole grain brown rice.Focusing on the above objectives,this thesis studied the relationship between the food quality of brown rice and the milling rate,as well as the effects of different processing methods and processing time on the microstructure,gelatinization properties and food quality of brown rice.Through the above research,the main results of this study are as follows:1)Different kinds of brown rice have different effects on food quality.Different milling rate of brown rice led to the opposite change of the basic component content and cooking quality.The high milling rate has the lower basic component content,and the better cooking quality.Among the three kinds of brown rice,Suijing-18 had the greatest change.When the milling rate increased from 0% to14%,the lipid and total dietary fiber content of Suijing-18 decreased by 71% and 74% respectively and cooking time reduced by 48%.However,protein content of Jingyue-1 has the greatest change and reduced by 25%;The volume expansion rate and water absorption rate of Longjing-31 increased by about 109% and 123%,respectively.2)The three processing methods can shorten the cooking time by changing the internal microstructure and morphology of brown rice particles.Among them,the high-energy particle bombardment and high-temperature gelatinization by low temperature plasma and superheated steam destroyed the ordered structure of starch,which significantly reduced the relative crystallinity and gelatinization enthalpy of brown rice(p<0.05),shorten the gelatinization process of brown rice,and thus significantly reduce the cooking time of brown rice(p<0.05),and close to the milling rate of 12%.The enzymatic hydrolysis assisted pregelatinization caused cracks in the cross section of brown rice through amylase hydrolysis of starch granules and pregelatinization,and the loose structure of brown rice increased the way for water to enter the granules,thus the cooking time of brown rice was significantly reduced(p<0.05)and lower than that of 14%.Among the three brown rice varieties selected,Longjing-31 was of short round grain type and had the lowest contents of lipid and protein.Therefore,the range of action of low temperature plasma,superheated steam and enzymatic hydrolyzation assisted pregelatinization on starch was increased.Therefore,the cooking time of Longjing-31 changed the most,shortening the cooking time by 29%,27% and 48%,respectively.The results showed that the most important factor affecting the cooking time was the loose structure of brown rice granules,followed by the ordered structure of starch.Therefore,among the three processing methods,the enzymatic hydrolyzationassisted pregelatinization had the best effect on the cooking time of brown rice.3)Viscosity characteristics also affect the food quality of brown rice.The peak viscosity of brown rice was significantly increased by low temperature plasma treatment(p<0.05),which resulted in increased viscosity and inhibited water flow,and significantly increased water absorption and volume expansion of brown rice(p<0.05)and higher than that of 14%.However,the partial gelatinization of superheated steam and the hydrolysis and gelatinization of starch by enzymatic hydrolyzation assisted pregelatinization led to the destruction of starch complex,which made the starch more easily combine with water.Therefore,the water absorption rate and volume expansion rate of brown rice increased significantly(p<0.05)and higher than that of 12%.Longjing-31 has the lowest lipid and protein content,so it is easier for low temperature plasma to act on starch.Therefore,the water absorption rate and volume expansion rate of Longjing-31 increased by 79% and 75%,respectively,after a long period of low temperature plasma treatment(32s).4)The lipid,protein and total dietary fiber contents of the three kinds of brown rice were not significantly lost by the three processing methods,and the cooking and food quality of the three kinds of brown rice were better than or close to the high milling rate samples.Therefore,the three processing methods can be used to produce nutritious and convenient brown rice products.The most significant processing effect is enzymatic hydrolyzation assisted pregelatinization,followed by low temperature plasma,and finally superheated steam.In the selected three kinds of brown rice,Jingyue-1 and Suijing-18 are long grain,but the lipid and protein content of Suijing-18 below Jingyue-1,so starch particles and ordered structures of Suijing-18 was more likely to be damaged by gelatinization and enzymatic hydrolysis of superheated steam and enzymatic hydrolyzation assisted pregelatinization.Therefore,Suijing-18 was suitable for processing technology of superheated steam and enzymatic hydrolyzation assisted pregelatinization.Longjing-31 is a short round grain type with the lowest lipid and protein content,which increases the range of starch etching by high-energy particles of low temperature plasma.Therefore,Longjing-31 is suitable for processing by low temperature plasma technology.