ACTA ALIMENTARIA VOL. 10 (A QUARTERLY OF THE COMMITTEE ON FOOD SCIENCE OF THE HUNGARIAN ACADEMY OF SCIENCES, 1981)
1981 / 1. sz. - KURUCZ-LUSZTIG, É.-PRÉPOSTFFY, M.-JERÁNEK, M.: Comparison of analytical methods used for the characterization of carbonyl content of fats
Acta Alimentaria, Vol. 10 (1), pp. 1—9 (1981) COMPARISON OF ANALYTICAL METHODS USED FOR THE CHARACTERIZATION OF CARBONYL CONTENT OF FATS É. KTJBTJCZ-LUSZTIG, M. PRÉPOSTFFY and M. JERÁNEK (Received: 6 October 1978; accepted: 19 March 1980) The analytical methods commonly used for carbonyl determination are reviewed here. Based on the evaluation of the literature, three methods have been adapted for the comparison of quality of various rape seed oils. The total carbonyl content has been assayed spectrophotometrically while both spectrophotometry and gas chromatography have been used for the determination of the volatile carbonyl content of the samples. The carbonyl index, which is proportional to the total carbonyl content of the sample, can be used to compare different raw and refined rape seed oils. The spectrophotometric volatile carbonyl assay can be used to detect the differences between raw and refined oils. Gas-chromatographic analysis of the volatile carbonyls allows for the detailed investigation of the individual carbonyls and the evaluation of the raw, refined and stored oils. Foods, including cooking fats, are traditionally subjected to sensory analysis with regard to both flavor and taste. Partial or complete replacement of the sensory evaluation methods has been intensively investigated over the past decades. Both recent technic al developments and the appearance of automated analytical instruments accelerated the replacement of the sensory evaluation methods. The taste and flavor of oil originate from characteristic compounds inherently associated with the particular oil and from the decomposition products of both the original fat and its contaminations. According to the ways of their formation, the volatile compounds present in fats can be classified (PREVOT, 1971) as follows. - Compounds originating from the natural flavor constituent of the oil. The concentration of these compounds in the refined oil is very low. - The second group of the volatile compounds is formed in the refined oil itself by the so-called flavor reversion mechanism. It is assumed that even slight oxidation of the refined oil results in the formation of volatile compounds. These compounds are believed to be formed by decomposition from the oxidized products not removed in the refining step, and not, as thought before, by oxidation following the deodorization. - The third group of the flavor compounds is formed by autoxidation. Hydroperoxides, the primary products of autoxidation are mostly tasteless compounds devoid of any characteristic odor. However, their decom- Acta Alimentaria 10, 1981