Impact of Conventional Processing Techniques and Growing Conditions on the Phenolic Content and Bioactive Compounds of Ethiopian Coffee Beans

Background and Objective: Growing conditions, roasting, and brewing methods are some of the factors and a sequence of procedures determining brewed coffee’s bioactive compounds and phenolic content. This work aimed to evaluate the impact of growing locations and efficient traditional coffee processing methods on better bioactive components and phenolic content of Ethiopian coffee. Materials and Methods: The efficient Ethiopian traditional coffee processing procedures with the commonly used medium particle size of coffee powder and widely used water type (surface water) were used for brewing by the Ethiopian traditional coffee brewing method (190°C of roasting, 16 min of brewing time). The HPLC was used to assess the phenolic content and determine the bioactive chemicals. The study used a two-factor factorial design with three treatment levels, considering roasting methods and coffee-producing areas (A and B). Data from five coffee origins were analyzed using ANOVA in SPSS (version 26) at a 5% significance level. Results: The caffeine content of Ethiopian Coffee Arabica origins ranged from 7.55 to 10.38 mg/mL, with Yirgachefe having the highest and Hararge the lowest (p<0.05). Chlorogenic acid levels were highest in Jimma, Sidama, and Nekemte (45 mg/mL) and lowest in Hararge (36.78 mg/g), while trigonelline was also highest in these three origins (p>0.05). Roasting significantly reduced total phenolic content (TPC) by an average of 27% and chlorogenic acid by 81% (p<0.05). Trigonelline decreased by 40% on average, with significant variation among coffee varieties (p<0.05). Conclusion: In general, the overall number of bioactive components and phenolic contents in processed coffee is influenced by growing regions and coffee processing. Further research may be necessary to determine how brewing temperature and extraction methods affect coffee’s phenolic content and bioactive components.