Effect of polydimethyl siloxane concentration on fatty acid and tocopherol degradation in soybean oil at high temperature

GERDE JOSE A.; HAMMOND EARL G.; WHITE PAMELA J.

Orlando, FL, USA

Conferencia; 100th American Oil Chemists’ Society Annual Meeting and Expo; 2009

American Oil Chemists' Society

The most accepted mechanism for polydimethyl siloxane’s (MS) protection of oil is that its surface accumulation prevents oxygen diffusion into the oil. Soybean oil containing 100, 50, 25, 10, and 5 ppb of MS and a control (no MS) were heated at 180 °C for 48 hr. The calculated amount needed for a surface monolayer of MS is 25 ppb. Both higher and lower concentrations than 25 ppb were tested. Fatty acid composition and tocopherol concentration were monitored. Slopes of the linear change in the ln (18:2/16:0) were calculated. For 50, 25, and 10 ppb MS inflection points were observed in these plots. The greater the MS concentration, the later the inflection point occurred, and for 100 ppb no inflection point occurred within 48 hr. At 5 ppb MS, the slope was not significantly different from that of the control. The slopes after the inflection points for 25 and 10 ppb were not different from that of the control. The smaller the MS concentration, the faster the degradation of gamma and delta-tocopherol. For all treatments gamma-tocopherol degraded faster than delta, possibly because delta spares the gamma analog. A decrease in the oil’s surface oxygen concentration was observed when 100 ppb MS was added, demonstrating that MS indeed acts as an oxygen barrier.