Degradation of phytosterols during storage of enriched margarines.

Oxidative changes of phytosterols were recently studied in vegetable oils and some food products. Cholesterol-lowering properties of phytosterols and phytostanols are the main driver for formulating functional foods containing these compounds. Margarines enriched in plant stanols were stored at two typical temperatures for up to 18weeks. Analysed margarines contained four phytosterols: brassicasterol, campesterol, sitosterol, avenasterol and two phytostanols: sitostanol, campestanol. The content of phytosterols and phytostanols in margarines changed from 79mg/g in a control sample to 63mg/g and 55mg/g in samples stored for 18weeks at 4°C and 20°C, respectively. At the end of storage, contents of sitostanol decreased by 23% and 30%, while the amounts of oxidised sterols increased by 35% and 100%, respectively, for both temperatures. 7-Hydroxy derivatives dominated among all oxidised phytosterols and their content increased threefold at the end of storage. Epoxy derivatives exhibited a maximum after 6weeks of storage at 20°C and thereafter decreased constantly.