揚げ油脂の種類と泡立ちについて

抄録

The objective of this work was to develop a practical method for monitoring the quality of oils during the frying process. Experiments were carried out on foaming of frying oils. In a previous paper, we compared the length of foam extension with the extent of deterioration of soybean frying oil, and it was observed that the foam was more extended according to deterioration. The rats fed oils with different degrees of foam extension showed growth depression with more than 32 mm of foam extension. Thirty-two of foam extension also corresponded to 21 mm of foam height. To know the relationship between kinds of oil and foam height during heating, oils (soybean, corn, olive and coconut oils) were heated at 180°C in fryer, and the changes of foam height, carbonyl and anisidine values, and/or oxidized fatty acids (fatty substances insoluble in petroleum ether) and tocopherol (Toc) contents were determined.
Higher foaming was observed in the case of coconut and olive oils and forming in soybean and corn oils was low. Carbonyl value, contents of oxidized fatty acids and thermal decomposition rate of Toc in oil by heating were higher for olive and cocount oils than for soybean and corn oils. The results suggest that high correlation exists among foam height, increase in carbonyl value, contents of oxidized fatty acids and the decrease of Toc in oils. Deterioration grade of frying oils collected from home and school refectory was low according to the measurement of foam height.