Safflower oil samples containing different amounts of the water dissolved in the oil were prepared and the influence of the water content on the autoxidation was investigated by measuring the peroxide value (POV) before and after the autoxidation in oxygen or air for 110h at 50°C.
In the autoxidation in oxygen, the influence of the water content may be discussed on the following two cases. The first case covers a range in which the water content is 20900ppm. In this case, the changes of POV decreased with decreasing amount of the water dissolved in the oil. The POV after autoxidation was 24.1 for the sample of 20ppm H
2O and 41.5 for that of 244ppm H
2O. But POV gradually rised in the range from about 200ppm to about 900ppm. The second case covers a range in which the water content is 9001815ppm. The POV after autoxidation was 42.3 for the sample of 948ppm H
2O and 57.8 for the sample of 1815ppm H
2O. If it is assumed that the water comprises the hydrogen-bonded water and the free water, the POV seems to increase in proportion to the amount of free water.
In the autoxidation in air, the influence of the water content may be grouped into two cases; one covering a range in which the water content is 10266ppm and the other covering a range in which the water content is 2661518ppm. In the former case, the changes of POV decreased with decreasing amount of the water dissolved in the oil. The POV after autoxidation was 0.8 for the sample of 10ppm H
2O and 4.6 for that of 266ppm H
2O. In the latter case, the POV after autoxidation was 4.6 for the sample of 266ppm H
2O and 8.3 for that of 1518ppm H
2O. The rate of autoxidation in air was markedly smaller than that in oxygen.
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