Abstract: In this research, RS3 type resistant potato starch was prepared and used as seed crystal to investigate the preparation of RS3 type resistant indica rice starch by the combined use of seed crystal and sequential hydrolysis with isoamylase and pullulanase. Scanning electron microscopy (SEM) was used to characterize starch granule morphology. Besides, we also studied the resistance of starches to enzymatic hydrolysis. Using the one-factor-at-a-time method, the amounts of seed crystal, isoamylase and pullulanase added and pullulanase hydrolysis time were identified as factors with a significant influence on the yield of RS3 type resistant starch. These variables were optimized using response surface methodology with a Box-Behnken design. The maximum yield of RS3 type resistant starch of 27.42% was obtained under the following conditions: 5% seed crystal, 8 U/g isoamylase, 8 U/g pullulanase and 3.50 h hydrolysis with pullulanase. The surface of the resistant starch granules was rough, which lost the original starch granule morphology, and the crystal structure of the resistant starch was compact. In addition, its resistance to enzymatic hydrolysis was strong.

Key words: seed crystal induction, RS3 type resistant indica rice starch, isoamylase, pullulanase