Bioactive diterpenes (cafestol and kahweol) in Turkish coffees: impact of roasting

While the cholesterol-raising effect of coffee has been ascribed to the presence of diterpenes, they have also been shown to present favourable health effects. Boiled-type coffees show slightly higher levels of diterpenes than those made with other brewing methods. However, there is considerable controversy regarding the effect of roasting on the contents of the diterpenes cafestol and kahweol. Therefore, the aim of the present work was to measure the contents of these diterpenes in Turkish coffees, and to determine how they are influenced by roasting. The samples used were 16 roasted and ready-ground Turkish coffees sold in supermarkets in the Turkish Republic of Northern Cyprus. The cafestol and kahweol contents of the coffee samples were analysed using liquid-liquid extraction followed by HPLC-DAD. The lipid contents of commercially roasted and ground Turkish coffee samples varied in the range of 14.32 ± 0.09 to 15.60 ± 0.09 g/100 g. The lipid contents of brewed Turkish coffee samples varied from 318 ± 2.00 to 571 ± 4.30 mg/100 mL. When compared within each commercial brand, dark roasted ground Turkish coffee samples had higher lipid contents. The average diterpene content in one cup of Turkish coffee sample was between 2.69 ± 0.28 and 13.58 ± 0.88 mg. The ranges of cafestol and kahweol contents in a cup were 1.4 ± 0.21 - 6.9 ± 0.65 mg and 1.28 ± 0.07 - 6.68 ± 0.28 mg, respectively. Within products of the same brand, the highest amount of oil was observed in dark roasted Turkish coffee beverages, and no significant differences were found in total diterpene, cafestol, and kahweol contents in coffee beverages among the different roasting levels. It is recommended that future studies perform more detailed investigations of the effect of roasting on the diterpene contents in Turkish coffees, and the impact of preparation parameters, as well as the presence of diterpene-derived compounds.