Description
TitleEvaluation of oxygen bomb methodology for studying frying chemistry
Date Created2010
Other Date2010-10 (degree)
Extentxvi, 136 p. : ill.
DescriptionOxipresTM oxygen bomb instrumentation was evaluated for measuring oxygen consumption in studying reactions of food oils at frying temperatures. High oleic sunflower oil:corn oil blends (60:40 w/w) were heated in OxipresTM cells over a range of temperatures from 100 to 180 °C under different gases and pressures. Effects of sample size, temperature, pressure, pressurizing gas, heating time, mixing, and oil characteristics were determined. Conjugated dienes, peroxide values, aldehydes, and free fatty acids were measured to relate oxygen consumption curves to other chemical changes during lipid oxidation. At 150 °C and above, oxygen consumption exhibited no induction periods and did not follow Arrhenius kinetics. Curves showed an initial pressure increase associated with oil heating, followed by a period of rapid decline, then a slowing in pressure decrease with continued heating. Limitations of oxygen diffusion may contribute to but do not fully explain this decreasing reactivity. Oxygen consumption rates and net uptake increased with headspace oxygen concentration (2, 5, 20, and 100%) and pressure (0.5 to 5 bars). The system accurately differentiated oxidation sensitivity of oils with different degrees of unsaturation with high reproducibility (average variation 2.27%). Oxygen consumption correlated with aldehyde oxidation products, particularly under high oxygen, but not conjugated dienes or hydroperoxides. Patterns of volatile products collected by short path thermal ii desorption tubes connected to Oxipres cells showed a homologous series of C2-C12 alkanes, alkenes, fatty acids, and aldehydes. These products are more consistent with thermal scission reactions than lipid autoxidation initiated by pre-formed hydroperoxides. Overall, the Oxipres system provides very stable, sensitive control of pressure and temperature, but three modifications would improve its design. At frying temperatures, headspace pressure reflects oxygen consumption balanced against release of volatile products and oxygen produced in reactions. Replacing the current pressure transducer with an oxygen-specific sensor would eliminate complications from volatile products. The closed system with slow eddy currents in the oil is a useful research tool but does not accurately model real-life frying. Addition of a stirring mechanism would facilitate oxygen diffusion. Finally, a thermocouple to monitor the actual oil temperature and rates of heating would be very useful.
NoteM.S.
NoteIncludes bibliographical references
Noteby Teng Peng
Genretheses, ETD graduate
Languageeng
CollectionGraduate School - New Brunswick Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.
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