Effects of drying methods on the retrogradation of rice

Hot- air drying,microwave drying,near infrared drying and vacuum- microwave drying were used to dry the fully gelatinized rice in order to reduce the degree of retrogradation.Rapid viscosity analyzer( RVA),differential scanning calorimeter( DSC),X- ray diffractometer( XRD),and scanning electron microscope( SEM) etc. were applied to observe the effects of different drying methods on the structure of rice. Results showed that the four kinds of drying method can well keep the good state of gelatinized rice and to a lesser extent of retrogradation.However,different drying methods impacted differently on rice tissue structure.The microwave vacuum drying had the greatest impact,which resulted in larger pores,and fluffy structure,as well as the highest( 5.2%) rehydration rate in the macro performance.