To gain an understanding of the mechanism by which silicone oil (SO) has effect on the dissolution of iron into fats and oils was examined.
1. Soybean oil and linseed oil with (0.1100ppm) or without SO were heated with iron plates in a beaker for 2, 4, 6h at 180°C, and the same oils (12.525g) were also heated on an iron plate (23×30cm) for 10 to 50min at the same temperature. The iron content in those heated oils was determined by the atomic absorption method. The content of iron in oils heated with SO was lower than in those without SO. Thus, SO may possibly prevent effectively the dissolution of iron into the heated frying oils.
2. Soybean oil with (1ppm) or without SO was treated with 5% of iron powder (wt/wt) for 10min at 100°C, and then filtered to remove the iron powder. The treated oils were again heated for 4h at 180°C, and the degree of oil deterioration was evaluated by the viscosity ratio, carbonyl and acid values and transmittance. The iron-treated oil with SO deteriorated much more than the non-treated oil. This appears to indicate that a certain amount of SO in iron-treated oil was adsorbed by iron powder.
The suppressing effect on the dissolution of iron into fats and oils is apparently one of the functions of SO in frying oil.