Analysis of Differently Roasted Arabica Coffee Samples by Electronic Tongue

Abstract

Abstract. In the coffee industry the degree of roast is determined by visual inspection of the color of the coffee beans or by measurement of the ground beans light reflectance. Because of the lack of an exact method the actual under and/or over roasting of the coffee can result in an off-flavor of the brewed coffee. The purpose of the work reported here was to reveal the possible off-flavors of differently roasted Arabica coffee samples by sensory evaluation and to check the ability of the electronic tongue to discriminate the samples by their degree of roast. Further aim was to find relationship between the results of color measurement and electronic tongue and to predict the degree of roast of some commercial coffee samples by the electronic tongue. For these purposes six differently roasted Arabica coffees and five commercial 100% Arabica coffee samples were analyzed. The attributes evaluated by the panelists were as follows: global aroma, acidic, bitter, roasted and coffee taste intensity and also the presence of the possible off-flavors. The results of the electronic tongue tests showed definite discrimination among the differently roasted coffee samples. The main differences were found between the light roasted and intensively roasted coffee samples (PC1-96.8%, PC2-3%). The degree of roast (color) was predicted by electronic tongue data with an R2 of 0.88. Among the sensory properties the prediction of the roasted attribute was the best, resulted an R2 of 0.9.