Unsaturated lipid matrices protect plant sterols from degradation during heating treatment

• The presence of fatty acid methyl esters slowed down plant sterols degradation at 180 °C.
• The presence and unsaturation degree of the lipid matrix delayed the POPs formation.
• Unsaturated fatty acid methyl esters reduced POPs formation.
• Both sterols and fatty acid methyl esters degradation fit a first order kinetic model.

The interest in plant sterols enriched foods has recently enhanced due to their healthy properties. The influence of the unsaturation degree of different fatty acids methyl esters (FAME: stearate, oleate, linoletate and linolenate) on a mixture of three plant sterols (PS: campesterol, stigmasterol and β-sitosterol) was evaluated at 180 °C for up to 180 min. Sterols degraded slower in the presence of unsaturated FAME. Both PS and FAME degradation fit a first order kinetic model (R2 > 0.9). Maximum oxysterols concentrations were achieved at 20 min in neat PS and 120 min in lipid mixtures and this maximum amount decreased with increasing their unsaturation degree. In conclusion, the presence of FAME delayed PS degradation and postponed oxysterols formation. This protective effect was further promoted by increasing the unsaturation degree of FAME. This evidence could help industries to optimize the formulation of sterol-enriched products, so that they could maintain their healthy properties during cooking or processing.