Effects of chain lengths and unsaturation degrees of fatty acids on microwave-processed wheat starch-fatty acid complexes: Structure, digestion, and storage stability

Wheat starch and fatty acid can combine as wheat starch-fatty acid (WS-FA) complexes playing crucial roles in health but are sensitive to ambient humidity. Therefore, microwave-processed WS-FA complexes incorporating fatty acids in different carbon chain lengths (C12 to C18) and unsaturation degrees (C18:0 to C18:3) were prepared, of which structural information, digestive characteristics and humidity-induced storage stability were investigated. Results showed that both chain lengths and unsaturation degrees of fatty acids affected the structural and digestive properties of WS-FA complexes. According to the moisture absorption behaviours, WS-FA complexes exhibited lower critical absorption relative humidities (CARH: 44 %-68 % RH) and equilibrium moisture values (Me: 17.7 %-20.5 %) than pure wheat starch (CARH: 72 % RH; Me: 27.7 %), indicating ambient humidity >44 % RH significantly impacts their storage stability. Beyond structural and digestive analysis, this study first investigates humidity-induced instability of WS-FA complexes for the first time, highlighting the need for customized standards for starch-lipid complex preservation.