ABSTRACT
Pressure-area isotherms of soybean oil monolayers on water were recorded under various conditions in order to study oxidation. The monolayers were exposed to air for different time periods and to the oxygen dissolved in the water. The slope of the pressure-area isotherms after collapse varied as a function of time and this was interpreted as being due to oxidation. The kinetics are of the first order type up to a point where the available double bonds seem to have reacted. The time of light exposure after aistillation of the water phase influenced the pressure-area isotherm and these changes were reduced by introducing an antioxidant into the subphase. During the compression of the monolayer, the triglyceride acyl chains experience different exposure to the oxygen depending on the structure of the two-dimensional phase. When the chains are closer packed in the monolayer, oxidation takes place at a slower rate. By changing the atmosphere from air to nitrogen, the influence of the oxygen in the air was followed.