Formation of Starch-Lipid Complexes during the Deep-Frying Process and Its Effects on Lipid Oxidation

In the present study, maize starch (MS), potato starch (PS), high-amylose maize starch (HAMS), and wheat starch (WS) were deep-fried in soybean oil that was continuously heated for 40 h under 180 degrees C. The thermodynamic and pasting properties of deep-fried starch samples were determined. The results suggested that starch-lipid complexes formed with the extension of frying oils' usage; however, their number was not dependent on the frying oils' life cycle. Importantly, the results of pasting properties revealed the following strength of intermolecular force in deep-fried starch samples: PS > MS > HAMS > WS. The results of XRD and FTIR analysis confirmed the formation of starch-lipid complexes during the deep-frying process. Furthermore, the results of the in vitro digestibility of deep-fried starch revealed that the formation of starch-lipid complexes inhibited the swelling of starch granules and prevented the entrance of amylase into the interior. Additionally, the results of the oxidation stability of deep-frying oil indicated that the formation of starch-lipid complexes did not alter the trend of lipid oxidation as an effect of the limited number of starch-lipid complexes. These results could have critical implications for the development of healthier deep-fried foods.