Effects of the extrusion and enzymatic extrusion treatment on the apparent viscosity of degerminated maize grits

Apparent viscosity is an important parameter for glucose syrup production.which is greatly affected by particle size and concentration of samples.In order to analyze the factors influencing the apparent viscosity,the particle size distribution,steady shear flow behavior,temperature,and time sweep test of native degerminated maize grits(NDMG),extruded degerminated maize grits(EDMG),and enzymatically extruded degerminated maize grits(EEDMG)with different particle sizes(passed through 20,40,60,80,and 100 mesh sieves)and concentrations(water-sample ratios:2:1,3:1,5:1,10:1,and 20:1)were investigated.All samples passed through different mesh sieves showed a gradient and a relatively concentrated distribution,and slurries had typical shear-thinning properties.Apparent viscosity increased with increasing particle size and concentration.The lowest apparent viscosity was attained from the samples obtained at 100+mesh and 20:1 water-sample ratio.Moreover,the sample with a 20:1 water-sample ratio showed the most stable apparent viscosity in the temperature sweep test.In the time sweep test,the power law equation with high determination coefficients(R^(2)=0.9446,0.9382)and low root mean square error(RMSE=0.0002)had the best fit to the experimental data of the EDMG and EEDMG samples passed through 100+mesh.Overall,the lower apparent viscosities of the EDMG and EEDMG samples obtained at 100+mesh and 20:1 water-sample ratio can improve the activity and accessibility of enzymes for glucose syrup production.This study provides critical insight into decreased apparent viscosity and expands the uses of EDMG and EEDMG in the glucose syrup sector.

Modification of physicochemical properties and degradation of barley flour upon enzymatic extrusion

In order to evaluate the application potential of enzyme-extruded barley flour(EEBF)in the brewing of whole-barley beer,the physicochemical properties,mashing and fermentation effects of EEBF were studied,and conventional extruded barley flour(CEBF)and steam-cooked barley flour(SCBF)were taken as controls.The water solubility index(WSI)of EEBF(46.88%-52.63%)was much higher than that of CEBF(6.70%)and SCBF(4.59%).The results of degree of gelatinization(DG)and enthalpy(ΔH)suggested that EEBF was almost completely gelatinized,and the rapid visco analyzer(RVA)exhibited that the peak viscosity of EEBF was drastically reduced.The weight-average molecular weight of EEBF(<10^(6) g/mol)was significantly lower than that of CEBF and SCBF.Scanning electron microscopy(SEM)showed that the heat-treatments caused starch granules to break and aggregate,and there were many hydrolyzed pores on the surface of EEBF.Both the long-and short-range order of EEBF were destroyed.Although EEBF caused serious filtration blocking,it greatly improved the alcohol content of finished beer(5.41%vol).Overall,the thermal modification of barley flour by enzyme-extrusion meets the needs of fermentation,and could improve the problem of limited leaching of unmalted barley,which was benefit for the production of whole-barley beer.