Oxidation of beta-sitosterol and campesterol in sunflower oil upon deep- and pan-frying of French fries

摘要

Fried foods, both deep-fried and pan-fried, are enjoyed by people worldwide. Frying is one of the main factors leading to formation of phytosterols (PS) oxidation products (POP) in vegetable oils. The aim of this study was to measure the oxidation of beta-sitosterol (24 alpha-ethyl-5-cholesten-3 beta-ol) and campesterol (24 alpha-methyl-5-cholesten-3 beta-ol) in commercial sunflower oil (SFO) during deep- and pan-frying of French fries for different periods (30, 60, 120 and 240 min). The total amount of PS in SFO was 4732 mu g/g, wherein the major PS were beta-sitosterol and campesterol. The results of POP were confirmed by the GC-MS analysis that monitored the formation of oxides during frying. Upon frying, total PS content decreased whereas the highest decrease was measured after 240 min of frying. The oxidative stability (OS) of different sitosterol and campesterol during both frying methods was evaluated. In general, pan frying resulted in more PS oxidation than deep frying. beta-Sitosterol oxides predominated while campesterol oxides were formed to a lesser extent. 7-Ketositosterol, followed by 7 beta-hydroxysitosterol, 5,6-epoxy derivatives and 7 alpha-hydroxysitosterol were the main POP induced during frying. The proportion of 7-keto derivatives decreased during frying while the proportion of 7 beta-hydroxy derivatives increased. The formation of POP might be a limiting factor for frying in SFO for long periods.