Analysis of minor components as an aid to authentication

Oil/fat Cholesterol Brassicasterol Campesterol Stigmasterol Sitosterol A5-avenasterol A7-stigmastenol A7-avenasterol Others Total (mg/kg) 

The most common sterols are A5-unsaturated desmethylsterols, but 4a-methylsterols and4,4-dimethylsterols occur at lower concentrations in vegetable oils. For example, sesame seed oil sterols are 85-89% des-, 9-11% mono- and 2-4% dimethylsterols (Kamal-Eldin and Appelqvist, 1994). The composition of monomethylsterol and dimethylsterol fractions of some oils is given in Table 6.2. 

Although many vegetable oils are quite similar in sterol composition, there are some important differences. Detection of brassicasterol can be used to detect adulteration of many oils by rapeseed oil as this sterol is only present in most oils in small amounts but rapeseed oil contains up to 780 mg/kg brassicasterol (see Table 6.1). The detection of adulteration of vegetable oils with animal fats can be achieved by analysis of the cholesterol content, since this sterol is either absent or present at very low concentrations in vegetable oils. 

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