Oxidation of sitosterol and campesterol in foods upon cooking with liquid margarines without and with added plant sterol esters

Plant sterol (PS) oxidation products (POP) derived from sitosterol and campesterol were measured in 15 foods cooked with liquid margarine without (control) and with added 7.5% PS. POP were analyzed using a GC-MS method. PS liquid vs. control margarine resulted in a higher median POP content per food portion (1.35 mg, range 0.08-13.20 mg versus 0.23 mg, 0.06-0.90 mg), a lower PS oxidation rate (0.63 vs. 1.29%) and lower oxidation susceptibility of sitosterol vs. campesterol. POP formation was highest in shallow-fried potatoes with PS liquid margarine (64.44 mg per portion food plus residual fat). Mean relative abundances of epoxy-, 7-keto-, 7-hydroxy-and triol-PS derived from sitosterol and campesterol were 40.0, 34.4, 21.5 and 4.0% with control vs. 44.1, 23.8, 29.6 and 2.4% with PS liquid margarine. In conclusion, PS liquid margarine increased POP content in foods with a POP profile characterized by a higher ratio of epoxy-to 7-keto-derivatives.