Journal of Lipid Research, Vol. 10, 555-560, September 1969
Copyright © 1969 by Lipid Research, Inc.
Ascorbic acid and copper in linoleate oxidation. I. Measurement of oxidation by ultraviolet spectrophotometry and the thiobarbituric acid test
Gottfried Haase and W. L. Dunkley
Department of Food Science and Technology, University of California, Davis, California 95616
The UV absorption method and the thiobarbituric acid (TBA) test for oxidation of an aqueous suspension of linoleate were compared. The absorption method depends on the formation of hydroperoxides having conjugated double bonds that absorb strongly at 233 nm. The absorption at 233 nm increased markedly during oxidation of linoleate catalyzed by either ascorbic acid or cupric ions. The concentration of ascorbic acid in the reaction mixture was also measured by UV absorption at 265 nm and pH 7.0.
Color development in the TBA test also increased markedly with the extent of oxidation of linoleate. When ascorbic acid was the catalyst, UV absorption detected early stages of oxidation with greater sensitivity than the TBA test. The reverse was true when Cu++ was the catalyst. In general, the relation between the two procedures will depend on whether copper is present when the TBA test is made.
Supplementary key words buffered linoleate model system • hydroperoxides • conjugated dienes • secondary products • metal contamination
Submitted on February 18, 1969
Accepted on June 2, 1969
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