Effect of repeated cycled crystallization on digestibility and molecular structure of glutinous Bora rice starch

•Repeated cycled crystallization slowed the digestion of waxy rice starch.•Molecular weight distributions of amylopectin were altered.•Loss of typical Maltese cross revealed reorientation of crystalline structures.•V-type complex observed in the SDS product even in the absence of co-polymers.

The effects of repeated cycled crystallization on the digestibility and molecular structure of glutinous Bora rice starch were investigated. Temperature cycle 4/45 °C; cycle duration 5 d; time interval of cycles 24 h; and starch to water ratio 1:2 were found to be optimum for SDS (slow digestible starch) product development. The SDS content increased from 18.01 ± 2.11% to 82.81 ± 2.34%. An increase in the resistance to digestion, crystallinity, molecular weight, polydispersity and molecular order was observed in the optimal SDS product. Notably, the FT-IR peak at 947 cm−1 and XRD peaks at 2θ ≈ 13° and 20° in the optimal SDS product indicated the formation of V-type complexes even without the presence of co-polymers. Birefringence studies showed a loss of typical Maltese cross in the SDS product and revealed a reorientation of crystalline structures within starch granules, suggestive of imperfect crystallite development.