Study On Processing Technology And Delaying Aging Of Fermented Semi-dry Rice Noodles

As a traditional staple food,rice noodles have a unique flavor.At present,the research on rice noodles mainly focuses on fresh wet rice noodles and dry rice noodles.However,fresh wet rice noodles are prone to spoilage and dry rice noodles take a long time to cook.Neither of these two kinds of rice noodles can fully meet the requirements of convenience and durability in modern society.In this regard,semi-dry rice noodles have comparative advantages,but they have received little attention.Therefore,it is of great theoretical significance to study the processing technology and quality change of fermented semi-dry rice noodles.In this paper,firstly,the processing technology of fermented semi-dry rice noodles was preliminarily established with early indica rice as the research object.And the effects of fermentation on gelatinization characteristics and thermal characteristics of rice were investigated.Then,the quality change of the semi-dry rice noodles during storage at room temperature was studied.Finally,the effects of corn starch,rice noodles Touzi and sucrose ester on the quality of fermented semi-dry rice noodles were studied,and the effects of these three modifiers on delaying the aging of rice noodles were explored.The main research contents of this paper are as follows:(1)Study on processing technology of fermented semi-dry rice noodles.The optimum processing technology of fermented semi-dry rice noodles was determined as follows:the amount of bacteria solution 4%,fermentation temperature 35℃,fermentation time 18 h,grinding particle size over 120 mesh sieve,moisture content of rice dough 60%,gelatinization temperature 95℃,gelatinization time 4 min.Under this process,the protein content of rice flour was 6.37%,the breakage rate of semi-dry rice noodles was 4.94%,the sensory score was 86.43,and the moisture content was 47.39%.It was found that the contents of basic components of rice were after fermentation,and the trough viscosity,final viscosity,setback and pasting temperature decreased significantly,while the thermal enthalpy increased significantly.This indicated that the fermentation treatment was beneficial to the gelatinization of rice flour and delaying the aging of rice noodles products.(2)Study on the change of storage quality of fermented semi-dry rice noodles.During the storage period of 180 days,the total number of colonies of semi-dry rice noodles increased gradually,reaching a maximum of 265 cfu/g,which did not exceed the safety standard.The storage period of semi-dry rice noodles could reach 180 days.With the increase of storage time,the breakage rate and cooking loss of semi-dry rice noodles increased to 7.60%and 10.43%,respectively,and the water absorption rate decreased to 48.51%.The semi-dry rice noodles were more likely to be broken and muddy when cooking.The color of semi-dry rice noodles became darker and yellower,and the acceptable degree of appearance decreased.The surface viscosity of semi-dry rice noodles increased,the taste became hard,and the elasticity decreased.The amplitude of viscosity,hardness and elasticity were 337.37%,126.78%and-4.23%,respectively.The thermal characteristics and X-ray diffraction(XRD)analysis results showed that the crystal structure of semi-dry rice noodles did not change during storage and was B-type crystal,but the thermal enthalpy and relative crystallinity of semi-dry rice noodles increased from 1.67 J/g and 3.48%to 4.21 J/g and 18.62%,respectively.It showed that the aging degree of semi-dry rice noodles increased.The study on nuclear magnetic resonance(NMR)analysis showed that the water in the semi-dry rice noodles mainly existed in the form of weakly bound water,and its content was more than 90%.In the process of storage,the internal water mobility of semi-dry rice noodles decreased,the degree of tight binding between water molecules and starch molecules increased,and the water distribution changed.After stored for 180 days,the weak bound water content in semi-dry rice noodles decreased by 3.71%,while the strong bound water content and free water content increased by 3.20%and 0.51%,respectively.The results of correlation analysis showed that hardness could be used as the core index of the texture parameters of semi-dry rice noodles.Through the correlation analysis of the indicators during storage of fermented semi-dry rice noodles,and the quality change of fermented semi-dry rice noodles was affected by the combined effects of microbial growth,aging of rice noodles and water distribution during storage at room temperature.(3)Study on delaying aging of fermented semi-dry rice noodles.First,through the determination of the hardness of semi-dry rice noodles,it was determined that the addition amount of corn starch was 8%,the addition amount of rice noodles Touzi was 8%,and the addition amount of sucrose ester was 0.5%.Then,the changes of cooking properties,gelatinization properties,rheological properties,thermal properties,crystallinity and water distribution of semi-dry rice noodles were compared after adding three improvers respectively.Adding 8%corn starch and 8%rice noodles Touzi could improve the cooking characteristics of fermented semi-dry rice noodles,and the breakage rate and cooking loss could be reduced by 27.98%and 23.18%,34.07%and 31.79%,respectively.Moreover,adding 8%corn starch and 8%rice noodles Touzi were beneficial to the formation of semi-dry rice noodles gel structure,and the gel strength could be increased.After adding 8%rice noodles Touzi and 0.5%sucrose ester,the aging degree of semi-dry rice noodles decreased,and the thermal enthalpy and relative crystallinity of semi-dry rice noodles decreased from 1.76 J/g and 16.01%to 1.23 J/g and 13.58%,1.25 J/g and 14.74%,respectively.And the effect of sucrose ester in delaying the aging of semi-dry rice noodles was not as good as that of rice noodles Touzi.After adding 8%corn starch,the thermal enthalpy and relative crystallinity of semi-dry rice noodles did not change significantly.The results of nuclear magnetic resonance analysis showed that the degree of freedom of water in the semi-dry rice noodles decreased after adding the improvers,and the water distribution changed.The addition of corn starch could increase the proportion of strongly bound water,decrease the proportion of weakly bound water and free water in semi-dry rice noodles.While the addition of rice noodles Touzi and sucrose ester could increase the proportion of weakly bound water and free water in semi-dry rice noodles,decrease the proportion of strongly bound water.Therefore,8%rice noodle Touzi could be added to improve the quality of semi-dry rice noodles and delay the aging of rice noodles.