Study On The Effect Of Low Molecular Weight Sugars On Pasting And Texture Properties Of Waxy Rice Starch

Gelatinized starch is easy to age during cold storage.Aging has bad effect on food quality and shelf life.Low molecular sugar can regulate properties of starch by interaction.In order to better understand the application of sugar in starch processing, this paper studied the effect of four low molecular sugars on the pasting and texture properties of waxy rice starch.The effects of low molecular sugar on pasting properties,enthalpy properties, texture properties and microstructure of waxy rice starch were investigated by Rapid Viscosity Analyzer(RVA),Differential Scanning Calorimetry(DSC),Texture Profile Analyzer(TPA) and Scanning Electron Microscope(SEM).The main conclusions as follow:The impact factors including lye density,treatment time and solid-liquid ratio on the removing rate of protein were studied by the orthogonal tests.Results as followed: lye density Na OH 0.2%, treatment time 2h, and solid-liquid ratio 1:6.Under those conditions, the content of protein was 0.34%.The pasting curve of waxy rice starch could reflect viscosity change of grain starch.The peak viscosity,trough viscosity and final viscosity were respecitively 108 RVU, 69 RVU and 78 RVU.With the addition of sugar,the hardness of starch gradually decreased,but the final viscosity,gelatinization temperature and chewiness increased.There was no significant change for springiness and cohesiveness. The final viscosity were reduced with monosaccharide and increased with disaccharide.The change of gelatinization enthalpy was increaed first then decreased.Sugar concentrationless less than 6%,the enthalpy of starch increased with the increase of sugar concentration, whereas more than 6%,the enthalpy of starch decreased.The syneresis% of starch gel was 5.9% after 1 freeze-thaw cycles.With freeze-thaw cycles increasing,the syneresis% first increased then decreased.With the addition of sugar,the syneresis% decreased significantly and the freeze-thaw stability increased.The hardness of starch increased effectively after freeze-thaw process,but springiness and cohesiveness reduced slightly.The addition of sugar made springiness and cohesiveness of gel increased.With increasing of monosaccharide,the hardness increased first then decreased,with increasing of disaccharide,the hardnaess decreased continously.The best content of sugar was 6% by the contrast.Further study found that the addition of sugar could improve the microstructure of starch gel by SEM.The gel surface became more smooth,the concave became smaller and the matrix became more compact.DSC test results showed that the ratio of melting enthalpy and gelatinization enthalpy decreased,the aging was inhibited,and the order of inhibition was trehalose>sucrose>glucose>fructose.