Dry heating and annealing treatment synergistically modulate starch structure and digestibility

Abstract

To modulate starch digestibility, dry heating combined with annealing treatment was employed to synergistically modulate structure and digestibility of normal maize starch (NMS) and potato starch (PS). Dry heating decreased starch molecular weight and created small molecular fractions with suitable chain length, resulting in starch better rearrangement during annealing treatment. Accordingly, after dry heating combined with annealing treatment starches had the highest pasting temperature, the thinnest and the thickest of crystalline lamellae for NMS and PS, respectively, and the highest ordered structures of cooked-starch compared with single dry heating or annealing modified starches. The results revealed that the synergistic modification altered starch lamellar thickness and increased double helices orders. Thereby, dry heating combined with annealing treated starches exhibited the lowest enzymatic digestibility with increased ca. 7.90% of slowly digestible starch for NMS or elevated ca. 5.04% of resistant starch for PS. The differential changes caused by dry heating combined with annealing treatment between NMS and PS were comprehensively discussed and the difference should result from the different starch crystalline structure and average chain length. This study provides a promising pathway for modulating starch structures and enzymatic digestibility.

Keywords: Annealing; Digestibility; Dry heating; Multi-scale structure; Starch.