When do starch-polyphenol complexes qualify as type 5 resistant starch? A critical evidence framework from molecular assembly to colonic utilization.

Abstract

Starch-polyphenol complexes are increasingly explored for modulating starch digestibility, developing low-glycemic-index foods, and improving polyphenol stability and delivery. Some systems have been described as type 5 resistant starch (RS5) or RS5-like based on V-type crystalline signals, increased resistant starch content, or reduced glucose release. However, these outcomes alone are insufficient for RS5 assignment because they may also arise from surface adsorption, non-inclusion networks, substrate shielding, enzyme inhibition by free or released polyphenols, or food-matrix effects. This review critically assesses the evidence required to describe starch-polyphenol systems as V-type starch-polyphenol complexes with demonstrated enzymatic resistance and examines their relationship to the proposed non-lipid extension of RS5. Evidence from molecular assembly, structural characterization, processing-induced rearrangement, resistance to enzymatic digestion, polyphenol release, colonic fermentation, and physiological relevance is integrated. V-type or V-type-like inclusion provides the strongest structural basis for identifying a V-type starch-polyphenol complex, whereas surface-bound complexes, non-inclusion networks and covalent derivatives require different mechanistic descriptions. Mechanistic attribution should include removal and quantification of unbound polyphenols, physical-mixture and washed-complex controls, and enzyme-inhibition kinetics. A tiered evidence framework is proposed to classify these systems as putative RS5, RS5-like complexes, polyphenol-bound resistant starch candidates, enzyme-inhibition-dominated systems, or non-RS mixtures.