FTIR-based structural interpretation of lipid oxidation in potato chips in relation to chemical indices

Abstract

Fat oxidation is an important factor for the quality and stability of fried products such as potato chips. However, the traditional chemical indices only give a partial characterization, without an explanation of the structural changes associated with this process. The present study was carried out to analyze the structural changes associated with oxidation using Fourier transform infrared spectroscopy (FTIR) and to correlate them with the chemical indices of oxidation in eight samples of potato chips. Spectra were acquired before and after oxidation and FTIR indices were calculated, such as carbonyl index (CI), unsaturation index (UI), phenolic index (PhI), oxidation index (OI), conventional oxidation indices (PV, p-AV, TOTOX) and total phenolic compound content (TPC). Results showed increase of CI and OI totals after oxidation, compared to decrease of UI and PhI, which indicates formation of secondary oxidation products and depletion of unsaturated fatty acids and antioxidant compounds. The CI showed positive and strong correlation with TOTOX (r = 0.85) and the UI exhibited negative correlation with p-AV (r = −0.79), whereas PhI showed positive and strong correlation with TPC (r = 0.91) confirming the ability of FTIR to represent the structural changes associated with oxidation and its defense against oxidation.Samples with faster oxidative behavior showed more pronounced structural change and differences in flavor could be related to differences in oxidative behavior, in accordance with their functional role as oxidation promoters or inhibitors, respectively, in previous work. These results indicate that FTIR is an effective analytical tool to interpret the oxidation pathway at the structural level and can be adopted as a complement to traditional chemical indicators to provide more comprehensive assessment of lipid stability in complex diets.