Physiochemical, structural and in vitro starch digestibility properties of starch blended with fish oil and wheat gluten

In this study, three component mixtures (TCM) were prepared by rapid visco analyser with wheat starch (WS), 15% of cod oil (CO), salmon oil (SO), coconut oil (CONT) and 10% wheat gluten (WG). The effect of the different inclusions on the physicochemical, structural and in vitro enzymatic properties of starch were evaluated, and the mechanisms involved between WS, CO, SO, CONT and WG observed. Results illustrated that significant decrease in peak viscosity and enthalpy values, and increased pasting temperatures of TCM samples, compared to WS and WG, due to the amylose–lipid complex formation. SEM images showed an embedded structure of starch granules while colour and textural indices of WS were significantly decreased in TCM samples. The findings of fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and 13C nuclear magnetic response (NMR) techniques showed that the structural changes occurred in TCM samples with more ordered structure of complex formation with starch-lipid and protein. Results exhibited a significant decreased in starch digestibility of TCM samples as compared to WS in order of CO > CONT > SO > WG > WS. Fatty acids present in the lipids appeared to form a complexed structure with amylose and inhibit the attack of digestive enzymes for hydrolysis. The findings of this study help to design food products with low digestibility and improved nutritional profiles.