Digestibility of resistant starch type 3 is affected by crystal type, molecular weight and molecular weight distribution

[Display omitted] •A-type RS-3 crystals are more resistant to digestion than B-type RS-3 crystals.•The higher the Mw of RS-3 preparations, the higher the resistance to digestion.•A low RS-3 polydispersity leads to lower digestibility.•A-type RS-3 crystals that escape digestion do not change in Mw (distribution).•Some B-type RS-3 crystals that escape digestion change in Mw (distribution). Resistant starch type 3 (RS-3) holds great potential as a prebiotic by supporting gut microbiota following intestinal digestion. However the factors influencing the digestibility of RS-3 are largely unknown. This research aims to reveal how crystal type and molecular weight (distribution) of RS-3 influence its resistance. Narrow and polydisperse α-glucans of degree of polymerization (DP) 14–76, either obtained by enzymatic synthesis or debranching amylopectins from different sources, were crystallized in 12 different A- or B-type crystals and in vitro digested. Crystal type had the largest influence on resistance to digestion (A >>> B), followed by molecular weight (Mw) (high DP >> low DP) and Mw distribution (narrow disperse > polydisperse). B-type crystals escaping digestion changed in Mw and Mw distribution compared to that in the original B-type crystals, whereas A-type crystals were unchanged. This indicates that pancreatic α-amylase binds and acts differently to A- or B-type RS-3 crystals.