Coffea arabica (Arabica) and Coffea canephora (Robusta) are two most widely used coffee species in commercial coffee food products. Coffea arabica is superior due to its favorable sensory properties and, therefore, remain in great demand in the global coffee market. However, the price of Arabica coffee is higher than Robusta since Robusta offer higher yield per plant and more resistant to pests and diseases during cultivation at less expensive agronomic conditions compared to Arabica. Therefore, several commercial brands of ground coffee are blended with Arabica and Robusta in order to achieve a flavor typical of that particular brand at a price that optimizes the market for that brand. 1H NMR spectroscopy have been used for identification of Arbaica and Robusta species in coffee beans and their food products. In this study we have investigated the adulteration of Arabica with Robusta in some commercial ground coffee products by monitoring the chemical shifts of diterpenes 16-O-methylcafestol (16-OMC) (chemical shift at 3.16 ppm) and kahweol (chemical shift :5.9 and 6.25 ppm) which are unique to Arabica and Robusta respectively. Their quantitative ratio distinguished the adulteration of Arabica and Robusta in 12 different commercial brands with 13-37% content of Robusta coffee. The inspection of adulteration in high-quality Arabica coffee with less expensive Robusta would provide a valuable indication of potential fraud in coffee products.
