Characterization and Quantification of Phenolic Compounds in Coffee Beans and Waste
Nine different types of coffee cultivars were used to study the effect of extraction time, extraction temperature, particle size and liquid/solid ratio on the phenolic compounds content, antioxidant activity and individual phenolic compounds profile. Samples were subjected to chemical compositions, mineral concentrations, total phenolic content, and antioxidant activity. Phenolic extracts were subjected to phenolic compounds content and antioxidant activity using different extraction conditions; each extract were subjected for determination of total phenolic compounds using Folin-Ciocalteu method, while antioxidant activity was measured using Methyl Linoleate (MeLo) assay. Results indicated the significant variations in chemical compositions and mineral concentrations. The total phenolic compounds content was 3.3 and 21 mg/100 g for coffee waste and green Guinea, respectively. Also, antioxidant activities had a significant variation 8.4 % for roasted Colombia and 19.7 % for green Guinea. The RP-HPLC profile for individual phenolic compounds contents showed that the gallic acid, protocatechuic acid, caffeic acid and vanillic acid were the major predominant phenolic acids in coffee beans and coffee wastes; while the caffeic acid was the dominating acid between 3.9 mg/100 g for coffee waste and 28.1 mg/100 g for green India. The highest total phenolic compounds content for all types of coffee beans was obtained using the following conditions of extraction; extraction time, 40 min; extraction temperature, 60 ºC; particle size, 0.68 mm, and liquid/solid ratio, 30 ml/g.
Keywords - Antioxidant Activity, Coffee Beans, Coffee Waste, Phenolic Compounds.