New insights regarding tocopherols in Arabica and Robusta species coffee beans: RP-UPLC-ESI/MSn and NP-HPLC/FLD study

Three tocopherol (T) homologues, namely α-, β- and γ-T, were quantified in Arabica and Robusta green and roasted coffee beans caffeinated and decaffeinated by normal phase-high-performance liquid chromatograph/fluorescence detector (NP-HPLC/FLD), and their identity was confirmed by reverse phase-ultra performance liquid chromatography-electrospray ionization/mass spectrometry (RP-UPLC-ESI/MSn). The alkaline saponification procedure, followed by extraction with a mixture of solvents composed of n-hexane:ethyl acetate (9:1, v/v), was applied to improve recovery of tocopherols from coffee beans. The average total tocopherol content recorded in coffee bean species was 10.93 mg/100 g (green Robusta), 28.07 mg/100 g (green Arabica), 11.54 mg/100 g (roasted Robusta) and 28.75 mg/100 g (roasted Arabica). The ratio between α:β:γ tocopherol homologues in Arabica green and roasted coffee beans was 1.4:4.7:0.1 and 2.6:8.1:0.1, respectively. Simultaneously, in Robusta green and roasted coffee beans this ratio was 1.2:1.4:0.1 and 1.7:2.0:0.1, respectively. Thus the unique tocopherol homologue ratio might be used as a tool to distinguish the coffee type (Arabica vs. Robusta). The δ-T, the fourth of tocopherol homologues, was not detected in any of the coffee beans studied. Roasting at a temperature above 180 °C for 10 min contributed to a decrease of tocopherol concentration. However, after 20 min of roasting a slight increase of tocopherol concentration was observed in both species.