Studies on the Behavior of Trace Components in Oils and Fats during Processing for Edible Use. II

Abstract

Five kinds of organochlorine pesticides and PCB were added to purified soybean oil and the oil was hydrogenated in a 20l autoclave under 11 different conditions, varying the amount of the catalyst, reaction temperature, and hydrogen gas concentration, but giving oils with almost the same melting points of ca. 35°C. The amounts of residual organochlorine pesticides and PCB were determined and change of the amount of these chemicals by hydrogenation condition was examined. (1) Amounts of these chemicals decreased markedly by hydrogenation but the degree of decrease was not uniform, there being a selectivity between the kind of catalyst used and the kind of organochlorine pesticide removed. The decrease was larger when the catalyst contained copper or chromium. DDT, Dieldrin and r-BHC were removed almost completely. (2) PCB also decreased by hydrogenation like the organochlorine pesticides and this decrease was especially great when the catalyst contained copper or chromium. A high residual rate was found when hydrogenation was carried out under a high pressure, using nickel catalyst alone, showing almost no removal of PCB. (3) Taking the decrease of organochlorine pesticides and PCB as a simple firstorder reaction, reaction rate constants under various hydrogenation conditions were calculated and they were found to be larger under high-pressure than under atomospheric pressure. This result suggested that the decrease of organochlorine pesticide and PCB during hydrogenation was due to the chemical changes such as reduction and dechlorination rather than their evaporation out of the reaction system.