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Oxidative Degradation Kinetics of Tocopherols during Heating
Hae Young Chung 한국식품영양과학회 2007 Preventive Nutrition and Food Science Vol.12 No.2
Tocopherols are important lipid-phase antioxidants that are subject to heat degradation. Therefore, kinetic analyses for oxidative degradation of tocopherols as a function of temperatures and times were performed. Alpha-, gamma- and delta-tocopherols dissolved in glycerol were heated at 100~250oC for 5~60 min. Oxidized tocopherols were analyzed by HPLC using a reversed phase μ-Bondapak C18-column with two kinds of elution solvent systems in a gradient mode. The degradation kinetics for tocopherols followed a first-order kinetic model. The rate of tocopherol degradation was dependent on heating temperatures. The degradation rate constants for γ- and δ-tocopherols were higher than those for α-tocopherol. The experimental activation energies of α-, γ- and δ- tocopherols were 2.51, 6.05 and 5.34 kcal/mole, respectively. The experimental activation energies for the oxidative degradation of γ- and δ-tocopherols were higher than that of α-tocopherol.
Formation Kinetic Study of Thermal Products of Tocopherols
Hae Young Chung 한국식품영양과학회 2007 Preventive Nutrition and Food Science Vol.12 No.3
The kinetic analyses for thermal products of alpha-, gamma- and delta-tocopherols during heating as functions of temperature and time were studied. Alpha-, gamma- and delta-tocopherols dissolved in glycerol were heated at 100~200oC for 5~60 min. The thermal products were separated by hexane extraction and analyzed by HPLC using a reversed phase μ-Bondapak C18-column with two kinds of elution solvents in a gradient mode. The formation kinetics of thermal products of tocopherols followed a first-order kinetic model. The formation rate of thermal products of tocopherols was dependent on heating temperatures and heating times. The activation energy and enthalpy for the thermal products of γ-and δ-tocopherols were higher than those for α-tocopherol as in the case of the oxidative degradation kinetics of tocopherol. The magnitude order of the activation energy was γ->δ->α-tocopherol.