Relationships between the evolution of the percentage in weight of polar compounds and that of the molar percentage of acyl groups of edible oils submitted to frying temperature.

The evolution of the molar percentage of several kinds of acyl groups of extra virgin olive, sunflower and virgin linseed oils was monitored throughout heating at frying temperature by means of (1)H nuclear magnetic resonance. Likewise, the evolution of the percentage in weight of the polar compounds of the same oils under the same heating conditions was also determined. Relationships between both sets of parameters, in each oil and in the oils as a group, were studied. An equation which is able to accurately predict the percentage in weight of the polar compounds, throughout the heating at frying temperature, of any one of these three oils, from the molar percentage of triunsaturated, diunsaturated and monounsaturated acyl groups, was obtained. In this way both molar percentage of acyl groups and percentage in weight of polar compounds can be obtained in a few minutes that registration of the (1)H NMR spectrum of the oil takes, in addition to the rest of information provided by this technique. The study reveals the close relationships between percentage in weight of polar compounds and the composition expressed in terms of molar percentages of acyl groups in edible oils heated at frying temperature.