Consumer and Food Sciences
MSc Food Science
Sensory profiling of selected Arabica coffees (Coffea arabica) of different Africa origins
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 from 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. Coffee proved to be a highly challenging matrix to study and required special preparation and presentation of individual samples at consistent temperature during sensory evaluation. Nevertheless, sensory profiles for the diverse range of coffees were achieved. Overall the samples grouped according to the geographical origin and the coffee samples all showed significant differences with regards to recorded sensory and physicochemical characteristics. Statistically significant differences were found between samples from different geographical regions in selected physical and chemical properties.
The African samples 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) 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.
About the project and personal experience
Coffee itself is an extraordinary product. It is a product made of passion and compassion in a world-wide industry. So much goes into the cup we have made accustomed to drinking as part of our daily routine. A few years ago I set a personal goal for myself to achieve a MSc degree, not only to improve my own knowledge and understanding from a scientific viewpoint on coffee and its sensory aspects, but also to engage in a worldwide network of academic professionals researching every detail of the product. As an industry professional a large part of my daily routine sits with evaluating the sensory aspects of coffee and this has truly inspired a love for African coffees. The 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 from Brazil. Researching more about African coffees, I realized that worldwide research information on the sensory profiles of coffees from African origins is specifically limited and my goal with the research project was to create an understanding of the subtle sensory differences in the different African origins that are key market players in the coffee industry as it stands today. 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. By defining coffees from African growing regions in terms of their sensory attributes, one could potentially not only improve the marketing of these coffees, but also potentially improve coffee qualities at a farm level. I very much enjoyed working with the product and was fortunate that I had access to some remarkable coffees by living in South Africa and working in the coffee industry. I must admit that I got discouraged on several occasions when doing my MSc, especially with the fact that I have a very demanding full time work, as well as with the addition of two children during the course of my studies, and I often felt overwhelmed and exhausted. However, in the end my love and passion for the product and with encouragement from my family and from the University under the supervision of Prof de Kock, success was inevitable. Today, looking back at it, it was well worth the time and effort and I will always be grateful for the guidance and encouragement I received from both Prof de Kock’s side and from my family.
Prof HL de Kock