| In this paper,starch was prepared from Anhui indica rice and glutinous rice.The starch and water were mixed at a ratio of 1:10,1:5,1:2.5(w/v),and gelatinized at 100? for 30 min.In the refrigerator at 4?,samples were sequentially chilled for Oh,3h,6h,12h,I d,3d,5d,7d,14d,21d,using spectrophotometer,water activity(Aw),low field nuclear magnetic(LF-NMR),Scanning electron microscopy(SEM),X-ray diffractometry(XRD),dynamic rheometer,etc.were carried out to study the starch composition,water molecule mobility,particle morphology,crystal characteristics and rheological properties of different concentrations of gelatinized starch.In order to provide a theoretical basis for the storage of starchy foods.The main results are as follows:1.The moisture content of indica rice starch and glutinous rice starch is about 10%,the starch is about 88%,and the protein,fat and ash content are low.The content of amylose in indica rice starch was 23.12%,the content of amylopectin was 76.88%;the content of amylose in glutinous rice starch was 0.49%,and the content of amylopectin was 99.51%.Observation by light microscopy showed that the indica rice and glutinous rice starch granules were similar in shape and similar in size,and the shapes were mostly triangular and polygonal.2.The solubility and swelling of indica rice and glutinous rice starch increased with the increase of temperature,and the freeze-thaw stability was different.The water leaching rate of 5%indica rice starch paste was 16.7%,and that of glutinous rice starch was 3.6%.The peak viscosity,bottom viscosity,final viscosity,peak time,retrogradation value,disintegration value and gelatinization temperature of indica rice starch are larger than the value of glutinous rice starch.3.The water activity value of the indica rice starch gel first decreased and then increased,and the aw containing 10%,20%,and 40%starch concentration gum began to increase on the 3th,5th,and 7th days respectively.The water activity value of glutinous rice starch gel has been decreasing.4.Refrigeration resulted in 10%,20%,40%concentration of indica starch gel,which appeared free flowing water in the 3th,5th,and 7th,respectively,while glutinous starch gel did not produce free water.5.Dynamic rheological analysis showed that the storage modulus(G')and loss modulus(G")of indica rice starch and glutinous rice starch gel increased with the increase of concentration and refrigeration days.At the same concentration,the energy storage modulus and loss modulus of indica rice starch gel were much higher than that of glutinous rice starch gel.6.The DSC aging peak of the indica rice starch gel appeared before the glutinous rice starch gel.20%indica rice starch gel showed an endothermic peak at 6h,and 20%glutinous rice starch gel appeared at Id.With the extension of storage time,the aging enthalpy of two kinds of rice starch gel increased at a uniform rate,but the final aging enthalpy of indica rice starch gel was higher than that of glutinous rice starch gel,which indicated that the aging degree of indica rice starch gel was greater than that of glutinous rice starch gel..7.After the rice starch is completely gelatinized,the crystal structure disappears almost completely,but there is still a microcrystalline structure inside the starch which is not completely gelatinized,and some characteristic peaks still exist,mainly around 170 and 20°.The characteristic diffraction peaks of 10%and 20%indica rice starch gel appeared at 12h and 6h respectively.The characteristic diffraction peaks of 10%and 20%glutinous rice starch gels appeared at 5d and 3d respectively,and the crystallinity increased with the storage time.The crystallinity of partially gelatinized indica rice and glutinous rice starch gel increased faster than that of fully gelatinized indica rice and glutinous rice starch gel... |
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