Effects of Conventional Processing Methods and Growing Locations on the Phenolic Content and Bioactive Compounds of Ethiopian Coffee Beans

Abstract Growing conditions, roasting, and brewing methods are among the factors and procedures that determine the bioactive compound and phenolic content of brewed coffee. This study aimed to evaluate the impact of growing locations and traditional coffee processing methods on the bioactive components and phenolic content of Ethiopian coffee. 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 0C of roasting, 16 min of brewing time). HPLC was used to assess the phenolic content and determine the bioactive chemicals. All five Ethiopian Coffee Arabica origins (Jimma, Sidama, Yirgachefe, Nekemte, and Hararge) had caffeine levels between 7.55 and 10.38 mg/mL. The coffee beans from Yirgachefe and Hararge had the greatest and lowest caffeine content, respectively (p < 0.05). The caffeine level of each variety varies significantly (p < 0.05), except for Nekemte and Yirgachefe. When compared to the other two coffee origins, the Jimma, Sidama, and Nekemte origins had the greatest levels of chlorogenic acid (p > 0.05), at 45 mg/mL. With 36.78 mg/g of chlorogenic acid, the Hararge cultivar had the lowest levels. Trigonelline levels were also highest in the Jimma, Sidama, and Nekemte coffee varietals, with 12.88, 13.56, and 13.46 mg/mL, respectively (p > 0.05). Hararge and Yirgachefe kinds had the lowest concentrations, with respective values of 11.65 and 11.78 mg/mL (p > 0.05). TPC was considerably lower after roasting all coffee beans (p < 0.05). The following coffee beans have the lowest proportion of TPC: Jimma (24%), Sidama (26%), Nekemte (30%), Yirgachefe (23%), and Hararge (29%). On average, the reduction was a 27% factor. After roasting, the caffeine concentration of the Sidama, Nekemte, and Yirgachefe coffee beans varied significantly (p < 0.05). Jimma (83%), Sidama (79%), Nekemte (82%), Yirgachefe (81%), and Hararge (82%), among all coffee origins, had the highest significant percentage decrease in chlorogenic acid content (p < 0.05). On average, there was an 81% decrease. Furthermore, there was a substantial variation in the trigonelline content across all coffee varietals during roasting (p < 0.05). With Jimma (54%), Sidama (29%), Nekemte (45%), Yirgachefe (38%), and Hararge (34%), the average reduction was 40%. In general, the overall amount 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 coffee's phenolic content and bioactive components are affected by brewing temperature and extraction methods.