Evaluating and improving the thermal stability of frying oil is of major concern for the whole frying industry, including oil producers and manufacturers of deep-fryers. Online measurements of oil degradation rely on coarse indicators such as total polar compounds (TPC) and free-fatty acids. We propose in this study to increase the "chemical resolution" of rapid tests by proposing point ATR-FTIR measurements for the local determinations of oxidation products in batch and continuous deep-fryers. Based on the deconvolution of four main regions of interest in the mid-infrared range and the identification of ten peaks, we describe the reconstruction kinetics of eight compounds or chemical functions. The whole methodology has been validated on the broad range of temperatures (140-180 degrees C), oxygenation conditions and oil composition described in Ref. [Patsioura et al., Food Bioprod Process Journal, 2017, 101, 84-99]. The study illustrated how the local oil composition can be used to discriminate oil oxidation pathways and to analyze the coupling between mass transport, heat transfer and oxidation reactions in connection with the deep-fryer design. An example of the local reconstruction of reaction schemes is detailed in inhomogeneous oxygenation and temperature conditions. (C) 2017 Elsevier Ltd. All rights reserved.