Study On The Effect Of Superheated Steam Treatment On The Quality Of Rice Flour And Instant Rice Noodles

Indica rice has a huge output in China,but it also has problems of large inventory and low utilization rate.Rice noodles are widely loved in China,especially convenient rice noodles.However,there are also many quality problems.This research use superheated steam treatment technology to solve the problems of convenient rice noodles,such as long rehydration time,fragile strips,and sticky,while helping to alleviate the current situation of large rice stocks in China,and provide a theoretical basis for the application of superheated steam in food processing.The rice was treated with superheated steam at 120℃,150℃ and180℃ for 0,2,4,6,and 8 min,respectively,and then milled to determine the particle morphology,composition,particle size,color,hydration characteristics,gelatinization characteristics,and thermal characteristics of rice flour,and propose the rice starch and protein separately,determine the particle morphology,polarized cross structure,long-range order structure,and short-range ordered structure,gel texture of starch,secondary structure,and molecular weight distribution of rice protein.Finally,convenient rice noodles are produced by a twin-screw extruder,measure the color,rehydration time,breakage rate,cooking characteristics(water absorption and cooking loss rate),texture characteristics(full texture characteristics and tensile characteristics)and sensory characteristics of the rice noodles,explore the influence of superheated steam treatment on the quality of the rice noodles,and explain its mechanism and find out the optimal processing conditions for rice to produce convenient rice noodles with good quality characteristics.The results show that:(1)The superheated steam treatment will significantly affect the amylose content,particle size and gelatinization characteristics of rice flour,and cause the "initial condensation" of steam,that is,the increase in the moisture content of rice.The increase of amylose content,trough viscosity,final viscosity and setback value,decrease in water absorption index,swelling potential,water solubility,attenuation value,phase transition temperature and gelatinization enthalpy are beneficial to the processing of rice noodles and make the rice noodles form a stable network Gel structure,not easy to break,cooking resistance,smooth taste,but high temperature and long time treatment will reduce the content and particle size of amylose,and increase the water absorption index,swelling potential,water solubility,and damaged starch content,which will affect the quality of rice noodles.The processing conditions should be controlled within 120℃,2 min to 150℃,6 min.(2)When the treatment intensity is high,the rice starch will aggregate,the polarized cross structure and the crystallization area will disappear,and the starch will undergo serious gelatinization.The low temperature and short time treatment will make starch and lipids form a complex,the order structure of starch will be reduced,the hardness and the adhesion of the gel will increase.After treatment,the α-helix in the rice protein decreases,the β-sheet increases as a whole,and the protein structure is more stable.When processing for 2 min,the amount of small rice protein soluble in SDS increases,but with the increase of the processing intensity,small analytical proteins will aggregate into 20 and 40 KDa proteins.Superheated steam changes the structure of starch,strengthens protein interaction,and forms starch-lipid complexes which are the reasons for the changes in the physical and chemical properties of rice flour.(3)Superheated steam treatment will not affect the color of instant rice noodles.Short-term treatment(2～6 min)can significantly reduce the rehydration time of rice noodles(reduce by 10% at 150℃,4 min),strip breakage rate(reduce by 10% at 120℃,2 min),cooking loss(reduce by about 5% at 150℃,2～6 min)and adhesion,improve the tensile strength and tensile breaking distance of the rice noodles,which is conducive to the improvement of the refreshment of the rice noodles,but the high temperature and long-term treatment will make the water absorption rate of the rice noodles.And the cooking loss rate increases,which adversely affects the structure of rice noodles.In summary,150℃ and 4min are the best superheated steam treatment conditions for rice.At this time,the rehydration time of rice noodles is shortened by 10% to 450 s,the stripping rate is reduced by 40% to7.3%,and the cooking loss rate is reduced by 5% to 13.6%,the sensory quality has also been improved.Proper treatment is conducive to the extrusion of rice noodles,the smoothness and flexibility of the mouthfeel,and the improvement of the cooking quality of the rice noodles.Excessive treatment will degrade the quality of the rice noodles.Conclusion: From a macro perspective,the superheated steam treatment can change the rice flour components,improve the hydration properties of the samples,its gelatinization properties and thermal characteristics,make amylose content,peak viscosity,trough viscosity,final viscosity and setback value increases,the particle size,water injectivity index,swell potential and water soluble,attenuation value,ΔH decreases.It has a positive effect on the quality of rice noodles.According to the microstructure analysis,the changes of starch structure,the strengthening of protein structure and the formation of starch-lipid complex were the reasons for the changes of physicochemical properties of rice flour during the process of superheated steam treatment.150℃ and 4 min were the optimal treatment conditions for rice,and the rice noodles at this time had the highest amylose content,28.2%.Compared with the untreated group,the rice noodles prepared were: the rehydrating time was shortened by 10% to 450 s,the bar breaking rate was reduced by 40% to 7.3%,the cooking loss rate was reduced by 5% to 13.6%,and the sensory quality was also improved to some extent.