食用油の加熱による揮発性成分について (第2報)

大豆油の熱分解生成物およびサフラワー油, オリーブ油の酸化生成物

抄録

1. Soybean oils, having the peroxide value of 10 and 290 respectively, were heated at 250°C under a stream of nitrogen. Volatile substances coming therefrom were caught in a trap cooled by dry ice-acetone, and then identified by gas chromatography. There were very little decomposition products from the soybean oil of the peroxide value of 10, most of which was hydrocarbons, contaminated with a small amount of carbonyls. As for the hydrocarbons, contents of olefins were higher than saturated hydrocarbons. In the case of the soybean oil of the peroxide value of 290, decomposition occurred mostly at an earlier stage of heating. The amount of decomposition products was much higher than that of the soybean oil of lower peroxide value. The gas chromatogram of the decomposition products at an earlier stage of heating was similar to that of thermal oxidation, and had large peaks due to n-pentane, propionic aldehyde and capronic aldehyde. The gas chromatogram of the decomposition products of the higher peroxide value soybean oil at later stage of heating was similar to that of the lower peroxide value soybean oil.
2. Volatile substances produced by heating safflower oil and olive oil in a stream of air at 250°C were identified by gas chromatography. As a result, some sorts of hydrocarbons and carbonyls were found in these volatile products, and their quantitative proportions were found to differ in accordance with the kind and quantity of fatty acids composing these oils-safflower, olive and soybean oil.
3. The quantitative proportions of these compounds in the volatile decomposition products obtained from these vegetable oils by heating at 250°C suggest that the decomposition of vegetable oil by heating at such high temperatures as 250°C is accompanied firstly by the formation of hydroperoxides and then followed by their cleavages on either side of the carbon atom containing the hydroperoxide group.