抄録
1. The object of this study is to elucidate the foam-forming properties and the chemical properties of oxidative-polymerized fractions in foaming oils, the contents of which caused durable foaming of oil by frying.
2. 100g of linseed oil, soybean oil and olive oil were heated at 200°C for about 4, 8 and 13hrs. in 300cc beakers respectively. At intervals of 30 minutes, a piece of potato was dipped in the oil to observe the oil foaming. Thus we could obtain (1) samples, one half part of the surface was covered by foams when a piece of potato was dipped in them and (2) samples, whole surface of which covered by foams, for each of the oils. We defined them as “the half-foaming oils” for the former and as “whole-foaming oils” for the latter.
These foaming oils were fractionated by the column chromatographic methods into 3 fractions. Silicagel treated with n-hexane containing 5% of i-propyl ether served as the absorbent. Foaming oil samples were eluted with 15% i-propyl ether in hexane to yield the first fraction (F1); with 60% i-propyl ether in n-hexane to yield the 2nd fraction (F2) and ethyl ether to yield the third fraction (F3).
The chemical properties such as the carbonyl value, acid value, hydroxyl value and mean molecular weight of F1, F2 and F3 were measured for various oils. The F2 and F3 thus fractionated from thermally oxidized linseed oil and olive oil were added to the original oils in various contents, then the foaming properties of these oils were measured. The measurement of foaming tendencies was carried out by gas pumping method, as reported in our former paper.
3. Experimental data showed that there was small variation in the foam-forming properties and in chemical properties of F3 fractionated from either of “half-foaming oil” and “whole-foaming oil” originated from the same oil.
The properties of F2 fractionated from various oils also resembled to each other. And foam-forming properties of F2 were weaker than that of F3. The F1 fractionated from various oils showed no forming property.
