Determination of the arabica/robusta composition of roasted coffee according to their sterolic content

A method for the determination Df the percentage of the arabica coffee in m ixtures of roasted coffee is proposed. The sterol content of roasted coffee blends was determined by extracting the coffee oil, saponifying the lipids and the sterols present in the unsaponifiable fraction were separated by t hin layer chromatography. Then, they were converted into trimethyl silyl de rivatives and analysed by gas chromatography. Twelve sterols were determine d in roasted coffee samples which were mixtures of the arabica and robusta classes. Considering the sterols as chemical descriptors, principal compone nt regression was applied. Delta(5)avenasterol was found to be a very adequ ate variable to establish the arabica percentage in roasted coffee blends. The method was applied to the determination of the arabica-robusta composit ion of commercial roasted coffee samples.