揚げ油におけるシリコーンオイルの機能について (第8報) : シリコーンオイル添加油脂の表面の状況の赤外部全反射吸収スペクトル法と光音響分光計による検索

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Methyl polysiloxane (SO) is frequently added to frying oils to inhibit for this thermal deterioration (oxidative polymerization). However, the mechanism remains unclear. Possibly SO forms a protective film on the oil-air interface to prevent oxygen from entering the oil. Though supported by many workers, this view is still only speculation.<BR>To confirm whether SO actually forms such a protective film, the following experiments were carried out.<BR>1) The attenuated total reflection (ATR) spectrum in the infrared area of tung oil differed somewhat from that of SO. The difference spectrum in the infrared area for this oil with and without SO clearly showed absorption attributable to SO, thus confirming the presence of SO at the oil-lithium fluoride interface.<BR>2) The photoacoustic spectrum (PAS) in UV region of tung oil differed completely from that of SO. Tung oil had strong absorption at 270280 nm and SO, none in the UV region. If the difference in peak heights at the absortption maximum in PAS for tung oil with SO and without SO may be assumed attributable to the existence of SO, the SO content on the surface of tung oil can be calculated from the ratio of the peak height of tung oil with SO to that without SO. The surface concentration of SO was found several ten times its bulk concentration.<BR>The present results demonstrate SO to be concentrated both on the oil-air interface and in oil-vessel interface.