Total contents of phenolics, flavonoids, tannins and antioxidant capacity of selected traditional Ethiopian alcoholic beverages
The aim of this study was to determine the total contents of phenolics, tannins and flavonoids and antioxidant capacity and their relationships in traditional Ethiopian alcoholic beverages. They have been determined utilizing Folin–Ciocalteu assay, aluminum chloride precipitating agent and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, respectively. The most widely consumed beverages and which have many varieties were selected for this study. These are gesho fermented and non-gesho beverages tella, tej, borde, keribo, birz, korefe and areke. The total phenolic content obtained in gallic acid equivalent (GAE) μg mL-1 was: areke (0.2–0.62), tella (10.1–19.1), tej (5.8–9.5), keribo (10.4–14.9), birz (10.5–12.2), korefe (9.2–10.7) and borde (8.4–10.6). The majority of phenolic compounds in the alcoholic beverages are non-tannic and non-flavonoid compounds. The antioxidant capacity obtained in ascorbic acid equivalent (AAE) μg mL-1 was: areke (-0.28–284), tella (31.6–201), tej (1.73–73.7), keribo (39.21–90.11), birz (41.95–63.08), korefe (58.25–96.45) and borde (180–217). The variation in the antioxidant activity among the beverages is due to the types and amount of ingredients used, disparity in the preparation process and the types of phenolic compounds found. The relationship between total phenolics and antioxidant activities was investigated using Pearson correlation at 95% confidence level. The results obtained indicate that the non-gesho fermented beverages such as keribo (-0.714), birz (-0.686) and borde (-0.212) have negative antioxidant correlation with the total phenolic, whereas, fermented beverages with gesho such as tella (0.539), tej (0.385) and korefe (0.557) have positive correlations. Areke has an overall positive correlation (0.609), but, the cereal areke which does not have medicinal plants has negative correlation.
KEY WORDS: Phenolic content, Antioxidant capacity, Traditional alcoholic beverages, Ethiopian beverages
Bull. Chem. Soc. Ethiop. 2016, 30(1), 27-37.