Complexation ability and physicochemical properties of starch inclusion complexes with C18 fatty acids

Starch, especially its amylose component, is well-known to form inclusion complexes with a variety of small molecules such as fatty acids. The structure of the lipid guest could affect its complexation ability and other properties such as thermal stability. The present study aimed to investigate the complexation ability and the physicochemical properties of high amylose maize starch (HAMS) inclusion complexes with C18 fatty acids of various numbers and positions of double bonds, including octadecanoic (stearic, SA), (Z)-octadec-9-enoic (oleic, OA), (E)-octadec-9-enoic (elaidic, EA), (9Z,12Z)-octadeca-9,12-dienoic (linoleic, LA), (9Z,12Z,15Z)-octadeca9,12,15-trienoic (alpha-linolenic, ALA), and conjugated linoleic acids (CLA). Two complexation methods were used, which are the DMSO method and the empty V-type method. The formation, structural characteristics, and thermal properties of inclusion complexes formed were examined by complementary techniques including differential scanning calorimetry (DSC), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy. As the guest fatty acid became more unsaturated and as the number of double bonds increased, the dissociation temperatures of HAMS-fatty acid inclusion complexes formed decreased with either complexation method. The DMSO method resulted in the formation of Form I inclusion complexes only, whereas the empty V-type method promoted the formation of Form II inclusion complexes with higher thermal stability. In addition, ethanol concentration was found to influence the formation of inclusion complexes when using the empty Vtype method, and intermediate concentrations were more favorable to maintain a stable and flexible amylose helical structure to form inclusion complexes with higher crystallinity and thermal stability.

Automated summary

The study investigated the complexation ability and physicochemical properties of high amylose maize starch (HAMS) inclusion complexes with C18 fatty acids of various unsaturation levels. The results showed that the thermal stability of the complexes decreased with increasing unsaturation of the guest fatty acid, with different complexation methods influencing the formation and stability of the complexes. Ethanol concentration was found to play a role in forming inclusion complexes with higher crystallinity and thermal stability.