Different effects of pectin and κ-carrageenan on the multiscale structures and in vitro digestibility of extruded rice starch

This study compared the different effects of pectin (PE) and kappa-carrageenan (CG) on the multilevel structures (i.e. granule, crystallites, helices, fractals, and short-range order) and in vitro digestibility of extruded rice starch (MERS). The addition of either PE or CG altered the multiscale structures, increased the resistant component (RC) content, and reduced predicted glycemic index (pGI), with CG being more effective especially at a low content. CG led to the growth of molecular aggregates (alpha), single-helices, and V-type crystals (X-V). PE resulted in higher contents of double-helices and A + B-type crystals (XA+B) and enhanced the short-range order (R-1045/1022) and particle compactness. Pearson correlation analysis indicates that, for MERS/PE, the slowly-digestible component (SDC) and RC contents were influenced by different factors in the sequence of total crystallinity (X-Total) > XA+B > X-V > single-helix content > alpha > R-1045/1022 > double-helix content. For MERS/CG, the RC content was affected by X-Total > single-helix content > X-V.

Automated summary

This study compared the effects of pectin and kappa-carrageenan on the multilevel structures and digestibility of extruded rice starch, with carrageenan being more effective at low content and pectin increasing double-helices and A + B-type crystal contents. The addition of either pectin or carrageenan altered multiscale structures, with carrageenan leading to the growth of molecular aggregates and single-helices, while pectin resulted in higher contents of double-helices and A + B-type crystals.