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Crystallization and gas liquid chromatography (GLC) have been used to characterize the triglyceride composition of olive and cottonseed oil and their precipitates from acetone or methanol/acetone (10:90, v/v) at −2 C. The precipitate obtained after a 24 hr crystallization of a 5% (w/v) solution of the sample in acetone or methanol/acetone (10:90, v/v) at −2 C was named Precipitate I (P-I); that isolated after 2 successive crystallizations under identical conditions was named Precipitate II (P-II). In each case, the ratio of oleic to linoleic acid (O/L) was calculated and proved to be a useful index for detecting adulteration of olive oil with cottonseed oil. In olive oil, the ratio O/L increased from the original sample to its precipitates, whereas in cottonseed oil and the adulterated samples the ratio O/L was lower in the precipitates than in the original sample. For olive oil P-II, the lowest value of the ratio O/L was 8.4; for the adulterated samples it was 7.6. On the basis of this index, adulteration of olive with cottonseed oil as low as 10% can be detected. Hydrolysis of P-1 by porcine pancreatic lipase and analysis of the fatty acids of the sn-2 position showed that the enrichment factor of linoleic acid varied between 1.11–1.30 for olive oil and between 1.55–1.90 for the adulterated samples. Even for adulteration with 5% cottonseed oil, the enrichment factor appears to increase (1.55–1.57) and can be used as a criterion for adulteration. |
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