Study On The Combination Of Extrusion And Microbial Fermentation To Improve The Quality Of Rice Paste

In this study,rice was uses as raw material,and twin-screw extrusion technology was adopted to pretreat and extrude the rice flour.After the composite microbial fermentation,the rice paste was prepared to solve the defects that the rice paste was easy to agglomerate and stratified,and consequently,making instant nutritious rice paste.The main findings are as follows:(1)Determining the optimal parameters for extrusion of rice flourThe effects of extrusion temperature,extrusion water content and extrusion screw speed on various indexes(gelatinization degree,puffing degree and water absorption)of rice bulking were studied,and orthogonal test design was used to optimize the optimal extrusion parameters of rice flour for microbial fermentation: the extrusion temperature is 125 ° C,the screw rotation speed is 190 rpm and the material moisture content is 22% to obtain the optimal extrusion expansion scheme.The extrusion expansion scheme results in a gelatinization degree of 96.7%,a degree of expansion of 3.315,and a water absorption rate of 711.96%.(2)Determining the effect of fermentation strains and fermentation parameters on the quality of extruded rice flourFirst,16 strains of Rhizopus isolated from the koji were subjected to morphological examination,α-amylase activity measurement,Felin reagent method test sugar,and neutralization method to determine total acid in order to determine the best Rhizopus strain.The results showed that the best Rhizopus was the number R6 strain,and the activity of producing α-amylase was 2.957 U/g,the test sugar was 24.4075 g / 100 g,and the total acid content was 1.061 g / 100 g.Number R6 Rhizopus strain was compounded with lactic acid bacteria and yeast for fermentation experiments,and the optimal fermentation scheme was optimized by measuring three indexes: glucose equivalent(DE)value,fermentation acidity and sensory evaluation: the optimum fermentation ratio was 1:2:1,the optimum fermentation time was 18 h,the fermentation temperature was 34°C,and the inoculum size of the strain was 5 g/100 g.The measured index was 66.7% for DE and49.9°T for acidity.The sensory evaluation score was 95.3.(3)Analysis of texture,brewing performance and quality of extruded puffed rice flourAfter the rice flour was extruded,the scanning electron microscopy revealed that the un-extruded rice flour(RF)had coarser surface and no pores;while the extruded starch granules expanded more,and have a sheet-like structure,the surface is smoother,the edges and corners are distinct,and the degree of damage is increased.The DSC study found that the peak temperature of RF is higher than the peak temperature of Extruded Rice Flour(ERF)and Extruded Fermentation Rice Flour(EFRF),moreover,the required heat absorption is higher and the thermal stability is lower than ERF and EFRF.XRD results showed that the crystallization peak in ERF disappeared by half due to effect of the high temperature and high pressure on the original type A crystal by extrusion,but the crystallization peak still showed the characteristics of type A starch.However,EFRF exhibits a crystalline characteristic peak of A+V type.Using solid phase microextraction combined with gas-mass spectrometry,it was found that compared to the rice flour,EFRF produced a lot of flavor substances such as ethyl acetate,so that the product has a unique fermentation flavor.After the experiment of brewing performance,it was found that the dissolving quality of rice flour was significantly improved after extrusion and fermentation.The dispersion coefficient,wettability index and brewing stability index of EFRF are better than RF and ERF.The optimum particle size of EFRF is 60 mesh(0.180~0.250mm),and the optimum brewing temperature is 80°C.The optimum ratio of solid to water is 1:6.Through EFRF component analysis and energy measurement,the protein content was 1.7561 g / 100 g,the crude fat content was 0.4861 g / 100 g,the ash content was 0.705 g / 100 g,the total dietary fiber was 2.6g / 100 g,and the total sugar content was 17.832 g / 100 g,a reducing sugar content of 3.18%,a carbohydrate content of 77.1%,an energy of 1889.6 kJ,and a sodium content of 0 mg / 100 g.After the comparative analysis of the composition of three kinds of rice flour,it can be known that the reducing sugar,total sugar and ash content of EFRF are significantly higher than ERF and RF,but the protein content and fat content of EFRF are lower than ERF and RF.