Study On The Factors And Mechanism Affecting The Grinding Methods And Pasting Properties Of Waxy Rice

Four varieties of waxy rice were used as raw materials in this subject.Three kinds of grinding methods including wet grinding,dry grinding and semi dry grinding were used to make waxy rice flour.The effects of different grinding methods on the quality of waxy rice flour were studyed.In order to find out the factors that influence the pasting properties of waxy rice flour and its mechanism,the activity of α-amylase and the pasting properties of waxy rice flour and waxy rice starch were determined.The relationship between the pasting properties,thermodynamic properties of waxy rice starch and its fine structure were studied.In order to figure out the factors and mechanisms that influence the hardness of uncooked waxy rice,The rice moisture content,grain size,density and hardness were measured and a soaking experiment was carried out.The main contents and conclusions of this research are as follows:(1)Wet grinding,dry grinding and semi dry grinding were used to make waxy rice flour,the quality of waxy rice flour was compared under different grinding methods.The results showed that the content of starch,ash and protein of waxy rice flour was the lowest by wet grinding method.The content of starch,ash and protein of waxy rice flour was the highest by dry grinding method.The content of starch,ash and protein of the waxy rice flour by semi dry grinding was between wet grinding and dry grinding method.The content of fatty acid value and damaged starch of waxy rice flour by wet grinding method was the smallest,the dry grinding method was the biggest and the half dry grinding method was among them two.Waxy rice powder particles are severely damaged with cracked surface and nonuniform size by Dry grinding method.In comparison with dry grinding method,semi dry grinding has less damage to waxy rice powder particles,and the particle surface is not too complete and the size of the particle is not very uniform.The waxy rice powder made by wet grinding method has a smoother surface,clear angle and uniform size.The particle size of waxy rice powder obtained by dry grinding is about 100μm,about 6μm by wet grinding,and about 50μm by semi dry grinding.The peak viscosity,grain viscosity and final viscosity of the waxy rice flour obtained by wet grinding were the highest.The peak viscosity,valley viscosity and final viscosity of waxy rice flour by dry grinding were significantly lower than that of wet grinding.The pasting characteristic value of waxy rice flour by semi dry grinding was between wet grinding and dry grinding.Different grinding methods have little effect on the crystallinity of waxy rice starch.(2)In order to study the factors and mechanisms that affecting the pasting propertiesIV of waxy rice flour,the activity of α-amylase and the pasting properties of waxy rice flour and waxy rice starch under different treatment conditions were measured,The results showed that the pasting properties of different kinds of waxy rice flour had obvious difference.The proximate analysis of four kinds of waxy rice flour had little difference,and the activity of α-amylase was quite different.From the results of correlation analysis,the content of protein has negative correlation with peak viscosity,valley viscosity and final viscosity of waxy rice flour but not significant.The values of α-amylase activity showed a significant negative correlation with peak viscosity,valley viscosity and final viscosity of waxy rice flour.The correlation coefficients were-0.958,-0.967 and-0.957 respectivily.It is shown that α amylase is one of the main factors that affect the difference of pasting characteristics of different waxy rice flour.After adding the silver nitrate solution to exclude the effect of α amylase,the pasting characteristic value of waxy rice which containing protein was lower than that of waxy rice flour after enzymatic hydrolysis,indicating that the protein in waxy rice flour is another factor that reduces the pasting characteristic value of waxy rice flour.(3)The relationship between the fine structure of waxy rice starch and the pasting and thermodynamic properties of waxy rice starch was studied.The experimental results showed that different varieties of waxy rice starch have different pasting and thermodynamic properties.The chain length distribution of the debranched starch is related to the pasting characteristics of the waxy rice starch,that is,the higher short chain ratio and lower long chain ratio result in a higher pasting peak value and lower gelatinization temperature.A higher crystallinity of waxy rice starch could cause a higher visicosity of pasting characteristic values.The higher the crystallinity of waxy rice starch,the lower the initial gelatinization temperature and the higher the pasting enthalpy of waxy rice starch.The crystallinity of waxy rice starch is lower,and the initial gelatinization temperature of glutinous rice starch is higher,and the pasting enthalpy is smaller.(4)In order to find out the factors that influence the hardness of uncooked rice and its mechanism the moisture content,density,hardness,grain size of uncooked waxy rice were determined and soaked the waxy rice in different times to determine the relations between hardness and soaking time.The experimental results showed that compared with fresh rice aging rice had lower on moisture content,density and hardness.The hardness of waxy rice has a certain relationship with the moisture content of uncooked waxy rice.Both fresh and aging uncooked DongBei japonica waxy rice has the highest moisture content and it turns out the lowest hardness.JiangXi indica has the lowest moisture content among the fresh waxy rice and turns out the highest hardness,YueNan indica hasthe lowest moisture content among the aging waxy rice and it turns out the highest hardness.With the increase of soaking time,the hardness of uncooked waxy rice decreased quickly within the first 60 min,dereased slowly between 60 and 120 min,and remained almost the same after 120 min,which may be attributed to the increase of moisture content during the soaking process.The higher the moisture content is the smamller the hardness becomes.