Influence of fat and phytosterols concentration in margarines on their degradation at high temperature. A study by 1H Nuclear Magnetic Resonance

• Margarines of similar composition in acyl groups were heated at high temperature.
• The process was followed by 1H NMR spectroscopy.
• Both thermo-oxidation and hydrolytic processes were contemplated.
• An inverse relationship has been found between thermo-oxidation rate and fat concentration.
• High phytosterols concentration slows down the margarine thermo-oxidation.

The objective of this work was to study the influence of several factors, especially fat and phytosterols concentration, on the behavior of margarine under thermo-oxidative conditions. For this purpose, margarines with similar compositions in acyl groups, but differing in the concentration of both fat and phytosterols, were heated at 180 °C. The changes in the main components of margarine lipids and the formation of new compounds throughout the thermal treatment were monitored by 1H Nuclear Magnetic Resonance. The results show that the presence of high concentrations of phytosterols seems to have an antioxidant effect, since it slows down the thermo-oxidation rate of margarine and, consequently, the generation rate and concentrations of secondary oxidation products such as some aldehydes, epoxides and alcohols. The oil–water ratio also seems to have an important effect on margarine behavior, in such a way that the lower the fat concentration is, the higher its thermo-oxidation rate.