Sterols heating: Degradation and formation of their ring-structure polar oxidation products

Cholesterol and phytosterols can be oxidised under heating conditions to give sterol oxidation products (SOPs), known by their toxic effects. This paper studied the degradation of cholesterol and three plant sterols during a 360 min heating treatment (180 °C). The formation and further degradation of SOPs was also analysed by GC–MS. Results revealed a sterol susceptibility to degradation according to the following decreasing order: campesterol ≈ β-sitosterol ⩾ stigmasterol > cholesterol. The degradation curve fit (R2 = 0.907–0.979) a logarithmic model. SOPs increased their concentration during the first 5–10 min and thereafter, their degradation rate was higher than their formation rate, resulting in a decrease over time. Irrespective of the sterol from which they had derived, 7-keto derivatives presented the highest levels throughout the entire process, and also SOPs with the same type of oxidation followed a similar degradation pattern (R = 0.90–0.99).