Sensory profiling of selected Arabica coffees (Coffea arabica) of different Africa origins

Abstract

Coffee is one of the world’s most important commodities, having economic importance to both the countries producing, and the countries consuming coffee. To ensure demand for coffee, it is of great importance to constantly maintain and, where possible, improve its quality. Flavour is crucial to coffee quality. However, describing coffee flavour is a very complex task as it is influenced by numerous factors from the farm to cup. Research information on the sensory profiles of coffees from African origins is specifically limited. By comparing the sensory and physicochemical characteristics of coffee from different African growing regions, the correlations between characteristics could be assessed, as well as similarities and differences identified. The ultimate aim of this project was to determine the effect of selected growing regions in Africa on the sensory and physicochemical characteristics of the coffee beverage, in comparison to each other and to coffee grown commercially in Brazil. Sensory evaluation of 20 coffee samples involved assessment of the brews, while physicochemical tests were completed on both the roasted beans and ground coffee, as well as the green coffee beans. Overall, the samples grouped according to the geographical origin and the coffee samples showed significant differences with regards to sensory and physicochemical characteristics.

The coffee samples from African origin differed significantly (p<0.05) from coffee samples grown in Brazil with regards to weight loss during roasting, roast coffee bean bulk density and moisture content. Differences were noted between samples from different growing regions for roasted coffee pH, total acidity, total fat content but no differences were noted between the African coffee samples in terms of total protein content, however the African coffee samples had an overall lower average protein content than Brazil coffee samples. From a sensory perspective, certain coffee were clearly more distinctive in sensory profile. The Brazil samples registered caramel-, fruit-, herb- and nut-like characteristics, whereas African samples had diverse floral-, fruit- and spice-like characteristics. Zimbabwe, Ethiopian Limu and Malawi samples registered more earth-, peanut-, cedar-, herb- and citrus-like qualities. Perceived acidity, perceived mouthfeel and perceived flavour intensity were evaluated over a time period (every 2 minutes for a period of 6 minutes, starting from the point water was added to the brew (time 0)) and significant differences were observed between different geographical growing regions as well as differences in perception over time. Significant differences were found in perceived acidity, body or mouthfeel over time between the different growing regions. At time 0, the Rwanda coffee samples had the most body or mouthfeel while the Malawi coffee samples had the least body or mouthfeel. It was also found that flavour intensity changed within the different samples over a time period of 6 minutes.

By defining coffees from African growing regions in terms of their sensory attributes one could potentially improve the marketing of these coffees but potentially also on the coffee qualities at a farm level.