Abstract:Comparison of the structural properties of resistant japonica starch prepared using various physical methods provides a theoretical foundation for industrial production. The resistant japonica starch (denoted as HMT-JS, PT-JS, and UT-JS, respectively) was prepared by the heat moisture method, the heat pressure method, and the ultrasonic method using japonica starch as raw material. The optimal preparation conditions were determined by single-factor tests, and the structure and properties of the resistant japonica starch under the optimal process conditions were investigated. The results showed that the optimum conditions for the preparation of resistant japonica rice starch by different physical methods were as follows: HMT-JS: moisture content of 20%, heat moisture time of 6 h, heat moisture temperature of 110 ℃, resistant starch content of 24.31%; PT-JS: starch emulsion mass fraction of 30%, heat pressure time of 30 min, heat pressure temperature of 110 ℃, resistant starch content of 16.68%; UT-JS: starch emulsion mass fraction of 30%, ultrasonic time 20 min, ultrasonic temperature 30 ℃, resistant starch content of 15.02%. Compared with japonica starch, the solubility and swelling power of the three resistant starches were reduced, the thermal stability was significantly improved, and they were less likely to regenerate, and the freeze-thaw stability also changed to different degrees; the rheological results showed that japonica starch and the three resistant starches were weak gel systems and pseudoplastic fluids; the surface of the three resistant starch granules became rough and adhered, and the relative crystallinity and short-range orderliness increased. The results of in vitro digestion tests showed that within the same hydrolysis time, the hydrolysis rate of the three resistant starches was lower than that of japonica rice starch, with HMT-JS having the lowest glycaemic index of 74.45%. The results of the study provide a reference for the development of deep processing products of japonica starch.