Abstract
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.
Highlights
Resistant starch (RS) is starch that resists digestion in the small in testine by human digestive enzymes and ends up in the colon
Narrow disperse α-glucans were enzymatically synthesized by potato glucan phosphorylase (PGP) and sucrose phosphorylase (SP) using debranched highly branched potato starch as primer molecule and sucrose as a substrate
At t = 0 min, the chromatogram shows several peaks which can be identified as malto-oligomers of debranched highly branched potato starch (dHBPS) and G-1-P formed after enzy matic hydrolysis of sucrose by SP (Fig. 1)
Summary
Resistant starch (RS) is starch that resists digestion in the small in testine by human digestive enzymes and ends up in the colon. To be able to act as dietary fibre, RS-3 preparations should be resistant to enzymatic digestion in the small intestine. It was suggested that RS-3 may be resistant to digestion due to slow enzyme binding of pancreatic α-amylase to the RS-3 crystals in combination with slow catalytic hydrolysis (Dhital, Warren, Butter worth, Ellis, & Gidley, 2017). It is not yet clear which physi cochemical characteristics of RS-3 cause the resistance to digestion. Differences in digestibility of RS-3 preparations might be caused by characteristics like crystal type and molecular weight (distribution) of the crystallized α-glucans
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