Analysis of Reaction Kinetics of Edible Oil Oxidation at Ambient Temperature by FTIR Spectroscopy

Abstract

Edible oils are studied to analyze their reaction kinetics during oxidation and predict shelf life at ambient temperature. Rapeseed oil (RO), soybean oil (SO), linseed oil (LO), and peanut oil (PO) are detected via Fourier transform infrared spectroscopy with a mesh cell as spectral acquisition accessory. The reaction kinetics of ROOH bonds, C═O bonds, trans double bonds (TDBs), and carbon chain skeletons (CCSs) are determined by absorbance changes in their characteristic absorption peaks. Prediction models for shelf life based on various characteristic absorption peaks are converted via the reaction kinetics equations of the oils. Results show that first-order reaction kinetics are used to describe absorbance changes of ROOH bonds in PO, SO, and LO, while zero-order reaction kinetics are used to describe the absorbance changes in RO. Both C═O bonds and CCS absorbance changes in the four oils satisfy first-order reaction kinetics. TDBs absorbance changes in PO, SO, and LO are in accordance with zero-order reaction kinetics. The regression equations of reaction kinetics exhibit good fitting degree (coefficient of determination, R 2 > 0.9000) and statistical significance (p < 0.001), indicating that the proposed method can be used to analyze the reaction kinetics of oil oxidation and predict shelf life. Practical Applications: The reaction kinetics of RO, SO, LO, and PO are studied at ambient temperature and the shelf life is predicted by using FTIR spectroscopy based on the absorbance changes of ROOH bonds, C═O bonds, TDB bonds, and CCS in the oils. The shelf life of edible oils can be more effectively predicted in this case and provide a practical reference for food industries. Furthermore, the proposed technique is rapid, green, and accurate, and allows real-time characterization of absorbance changes in various characteristic absorption peaks, which corresponded to different oxidation products. By this method, it is possible to reflect real-time information for different quality indices (such as peroxides and acid values) of oil oxidation simultaneously, and unnecessary to measure these indices directly one by one, saving manpower and material resources. Therefore, FTIR spectroscopy is convenient for the rapid evaluation of oxidation stability and shelf life of edible oils under ambient temperature.

Effect of Alkaline Salts on Pyrolyzed Solid Wastes in Used Edible Oils: An Attenuated Total Reflectance Analysis of Surface Compounds as a Function of the Temperature

“…It is observed that th It needs to be noted that the low intensity of the bands in the 900-700 cm −1 region and the overlap with that at 723 cm −1 for the S-300 sample made it impossible to estimate the DOC, and therefore, this solid is not considered in Figure 6. It is observed that the DOC of the PAH increases up to ~500 • C, which is in good agreement with the data in the literature [18,32], but at T > 500 • C, the DOC strongly decreases, contrarily to what was expected. It was supposed that this effect was caused by the presence of inorganic salts in the raw material, and experiments that were designed to confirm this point were carried out.…”

“…The DOC calculated as a function of the temperature (black line in Figure 6) increases to 500 °C and decreases for higher temperatures, contrarily to the data reported in the literature [32]. The observed trend suggests that the cracking reaction (1) occurs at T > 500 °C, but the condensation reactions seem to be limited.…”

“…This is in line with the data in the literature reporting that aromatization reactions occur in the early steps of pyrolysis [18,19], increasing the PAH yields. Moreover, bands due to chain C-O and CH2 vibrations together with the band at 723 cm −1 decrease, evidencing the breakdown of the hydrocarbon chains via a thermal effect or a reaction [31,32]. This decomposition can result in the formation of small hydrocarbons that pass to the gas phase, which explains the low H/C ratio measured for biochars (Table 1).…”

“…In relation to the DOC of the PAH, the mechanism proposed in the literature is summarized in Scheme 1. At temperatures higher than 500 • C, PAHs partially crack to form unstable radicals that, through condensation reactions, produce PAHs with a higher number of aromatic rings in their structure, that is, a higher DOC [32].…”

Kinetics of extracting valuable components from Ti-bearing blast furnace slag by acidolysis with sulphuric acid

“…Therefore, the data before the reaction stabilizes in Figure 4 are fitted by substituting the equation in Table 3 and the fitting results are shown in Figures 5 , 6 . The kinetic fitting model is considered to be well fitted when the correlation coefficient ( R 2 ) is greater than 0.85 ( Wang et al, 2020 ; Li et al, 2023a ), which shows that the R 2 between the internal diffusion Equation (1) + 2(1 – r) – 3(1 – r) 2/3 and time t is greater than 0.85 for different acid-slag ratios, acidolysis temperatures and TBFS particle sizes. It can be assumed that the acidolysis reaction rate is mainly controlled by the internal diffusion of H 2 SO 4 in the product layer ( Zhang et al, 2023 ).…”