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Oxidation degree of soybean oil at induction time point under Rancimat test condition: Theoretical derivation and experimental observation
- Li, Xu, Li, Yongru, Yang, Fan, Liu, Ruijie, Zhao, Chenwei, Jin, Qingzhe, Wang, Xingguo
- Food research international 2019 v.120 pp. 756-762
- acid value, butyric acid, cooking fats and oils, equations, fatty acid composition, ion exchange chromatography, models, nuclear magnetic resonance spectroscopy, oxidation, peroxide value, shelf life, soybean oil, temperature
- Indices including conductivity, short-chain carboxylic acids, total polar material, acid value, peroxide value and fatty acid composition in water or oil were monitored during Rancimat test of soybean oil from 90 °C to 120 °C. Formic, acetic, propionic and butyric acids in water were detected by ion chromatography. The results showed that all indices had two-stage oxidation rates of initiation (ki) and propagation (kp) at each temperature. Induction period (IP) computed from conductivity and other indices were well correlated (R2 = 0.9980–0.9999). According to the Arrhenius model and empirical equation, ki increased exponentially with temperature (T) while IP decreased exponentially with T. Oxidation degree of oil at induction time point IP*ki was found to be independent of heating time and temperature. The transition between two models was theoretically derived and proved by H NMR. Evaluation of IP*ki may provide a new route to correlate Rancimat data with shelf life of edible oil.