食用油脂の示差熱分析 (第5報) : 植物油脂の連続降昇温示差熱分折について

概要

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Continuous cooling and heating differential thermal analyses (DTA) were carried out in a low temperature range, at the rate of 5°C/min, with 14 samples of refined or refined and winterized six kinds of vegetable oil. DTA curves of these oil samples were found to show considerable distinctive features.<BR>1) Cooling DTA curve of cotton-seed oil showed an appreciable exothermic peaks at 7° and -12.5°C, but after wintering, the peak at 7°C disappeared and that at -12.5°C became small. A considerable change was also seen in the heating DTA curve.<BR>2) Cooling DTA curve of rice oil had three exothermic peaks at -19°, -39° and -77°C but after wintering, the peak at -19°C became small. Such a difference was not seen in heating DTA curve.<BR>3) Corn oil, safflower oil and soybean oil all showed different peak temperature in their DTA curves but all had three exothermic peaks. The peak in the lowest temperature side were larger in salad oils of corn and safflower, while the three peaks in the salad oil of soybean transited to the lower temperature side. In heating DTA, curves of corn oil and soybean oil were similar, and there was no difference from those of their salad oil.<BR>4) The cooling DTA curve of rape-seed oil had a large and very sharp exothermic peak at -41°C, and two large endothermic peaks at -20° and -7°C, and a small exothermic peak at -5°C in heating DTA curve. There was no difference the DTA curves of its salad oil.