Effects Of Three Physical Treatment Methods On The Physicochemical Properties Of Broken Indica Rice Flour

In southern China,indica rice is a large output crop,wheares,it has low vendibility as the low viscoelasticity and poor taste after being gelatinized.During the process,10-15%broken rice grains are generated.Broken rice,which has a similar chemical composition to that of whole rice,significantly reduces the commercial value of the rice cultivar.As a result,broken rice has been subjected to different physical modification methods(superfine grinding,ultra-high pressure,extrusion,and combined treatments),the rice flour characteristics including nutritional,pasting,gelatinization,retrogradation,rheological,and structural characteristics was studied.The study was conducted in anticipation that it could contribute reference for the processing and applications of broken rice.1.Compared with natural rice flour,superfine grinding resulted in low protein,fat,total starch contents,but higher amylose contents.The chemical properties of ultra-high pressure rice flour was similar with natural rice flour.Extrusion treatment resulted in low protein,fat,and total starch contents,but higher amylose contents.2.Compared with natural rice flour,superfine grinding rice flours had higher solubility but lower swelling,the freeze-thaw stability and in vitro digestibility of superfine grinding rice flour were improved.There was no significant difference between natural rice flour and ultra-high pressure rice flour.The extrusion rice flours had much higher solubility but lower swelling,the freeze-thaw stability and in vitro digestibility of superfine grinding rice flour were improved greatly.3.The result of dynamic rheology of rice flours indicated: compared with natural rice flour,superfine grinding rice flours had higher storage modulus and loss modulus,the loss tangent of superfine grinding rice flours had no difference with that of natural rice flour;The storage modulus and loss modulus of ultra-high pressure rice flours were lower than those of natural rice flour.The result of steady shear of rice flours indicated:Herschel-Bulkley model gave a good fit for all samples(with concentration 3%)with high coefficient of determination;Compared with natural rice flour,superfine grinding resulted in small hysteresis area but high consistency coefficient;The steady shear properties of ultra-high pressure rice flour was similar with natural rice flour;Extrusion treatment resulted in very small hysteresis area and consistency coefficient.4.Compared with natural rice flour,superfine grinding rice flours had higher peak viscosity,trough viscosity,final viscosity,setback,but lower breakdown;The peak temperature of superfine grinding rice flours were higher than that of natural rice flour,themelting enthalpy of superfine grinding rice flours was opposite;The percentage of retrogradation and retrogradation rate of superfine grinding rice flours increased.Ultra-high pressure treatment had no effects on the pasting and retrogradation properties of natural rice flour.Extrusion rice flours had much lower peak viscosity,trough viscosity,final viscosity,breakdown and setback than those of natural rice flour;The peak temperature and melting enthalpy of extrusion rice flours were lower than those of natural rice flour;The percentage of retrogradation and retrogradation rate of extrusion rice flours decreased.5.The results of crystalline of rice flours indicated: The natural rice flour,superfine grinding rice flours and ultra-high rice flour both had strong diffraction peaks at 15� and23� and weak peaks at 17� and 18�,these results indicated that these rice flours had distinct A-type diffraction pattern;the crystallinity of natural rice flour was 12.8%,the crystallinity of superfine grinding rice flours and ultra-high rice flour were similar to natural rice flour.The extrusion rice flours both had diffraction peaks at 13� and 20�,had distinct V-type diffraction pattern;the crystallinity of extrusion rice flour was 2.1%,extruded and superfine ground rice flour was 2.3%,which were significant lower than that of natural rice flour.