Effects of fatty acid chain length on structure and in vitro enzymatic digestibility of type 5 resistant starch

Summary The effects of saturated fatty acids with different chain lengths (C12, C14, C16, C18) on the structure and digestibility of type 5 resistant starch (RS5s) were investigated. The complexing index (CI), structure, phase transition temperature, digestibility and evaluation glycemic index (e GI ) values of RS5s were determined. High‐amylose corn starch VII (HA7) ‐ myristic acid (MA) complex had the highest CI value (41.1%), relative crystallinity (40.4%) and 1047 cm −1 /1022 cm −1 (1.0), smallest full width at half maximum (fwhm) of the band at 480 cm −1 (16.4), indicating that RS5 with 14‐carbon saturated fatty acids was more easily to form V‐type crystal complexes with amylose, and the long‐range and short‐range molecular orderliness was the best. With the increase of the carbon chain (12 ~ 18), The peak temperature (Tp) of the complexes gradually increased from the HA7‐lauric acid (LA) complex (112.8 °C) to HA7‐stearic acid (SA) complex (119.1 °C). The content of slow digestible starch (SDS) and e GI values gradually decreased ( P < 0.05), and the content of resistant starch (RS) significantly increased ( P < 0.05). These results indicated fatty acid chain length and long‐range molecular orderliness were the main factors affecting the digestibility of RS5s.