Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Food Technology


Randomization of fat usually causes an increase in its rate of autoxidation. The reason for this is unclear. To study this, natural and randomized corn oil were purified by passage through alumina and oxidized to peroxide values of 30 to 40 at 28 C. The hydroperoxides were reduced to alcohols with iodide. Two major bands of oxidized products were separated from the unoxidized triglycerides by thin-layer chromatography on Silica gel G. The lower band was a triglyceride containing one hydroxyacyl group. The upper band was a triglyceride containing an azelaic semialdehyde or methyl azelaic group. This band also contained an unidentified aldehyde that had a molecular weight of 152 and probably a furan ring. The proportion of the upper band was two times greater in randomized than natural corn oil at similar peroxide values;Corn oil methyl esters were prepared with methanolic sodium methoxide, purified and oxidized as before. Two major bands of oxidized products were also separated from unoxidized methyl esters. The upper band consisted of dimethyl azelate, methyl azelaic semialdehyde, nonanal and the same unidentified component as in the oxidized oil;Results from oxidative rate studies showed that randomized corn oil oxidized three to four times faster than natural corn oil, and corn oil methyl esters oxidized approximately as fast as randomized oil. This suggested that the natural glyceride structure of corn oil may affect its oxidative rate. Another possible explanation could be that unknown antioxidants or pro-oxidants are present. However, neither speculation can fully explain the difference observed in oxidative rates and the amount of scission products formed in oxidized randomized and natural corn oil.



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Flora Yu-man Lau



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74 pages