Structural and in vitro starch digestion properties of starch‐fatty acid nanocomplexes: effect of chain lengths and degree of unsaturation of fatty acids

Abstract BACKGROUND The structural and digestion properties of starch‐lipid complexes are closely related to the properties of lipids. The chain length and degree of unsaturation of fatty acids (FAs), which can affect the structural and digestion properties of starch‐lipid nanocomplexes, therefore need to be examined in detail to gain a better understanding of this. In this study, the effects of chain length (10–18 carbons) and degree of unsaturation (0–2) of FA on the structural and in vitro starch digestion properties of high amylose corn starch (HAS)–FA nanocomplexes were investigated, as was the correlation between their structural alterations and digestibility. RESULTS This study showed that HAS–FA nanocomplexes with 10‐carbon (38.55%) and 12‐carbon (44.56%) FAs displayed high‐resistant starch (RS) and slowly digestible starch (SDS) content, whereas those with 18‐carbon FAs with two double bonds exhibited low RS + SDS content (23.41%). The complexing index, R 1047/1022 , relative crystallinity, and enthalpy change in the HAS–FA nanocomplexes also increased with the reduction in the chain length (except for 10‐carbon FA) and the degree of unsaturation of FAs, whereas the equilibrium hydrolysis percentage, kinetic constant and apparent amylose content showed an opposite trend. CONCLUSION Chain length and degree of unsaturation of FAs affected the digestibility of HAS–FA nanocomplexes. The HAS–FA nanocomplexes with 12‐carbon FAs displayed high RS + SDS content with higher degrees of molecular order at long‐range and short‐range levels. Results provided guidelines to regulate the digestibility of starch‐fatty acid nanocomplexes by varying the FA structures. © 2022 Society of Chemical Industry.