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

Abstract

A method for the determination of the percentage of the arabica coffee in mixtures 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 thin layer chromatography. Then, they were converted into trimethyl silyl derivatives and analysed by gas chromatography. Twelve sterols were determined in roasted coffee samples which were mixtures of the arabica and robusta classes. Considering the sterols as chemical descriptors, principal component regression was applied. Δ⁵avenasterol was found to be a very adequate variable to establish the arabica percentage in roasted coffee blends. The method was applied to the determination of the arabica–robusta composition of commercial roasted coffee samples.