Atividade antioxidante, antibacteriana e antifungica de extratos de café verde e torrado

Abstract

Coffee is one of the most popular drinks in the world. As a commodity, the presence of defective grains, which make up about 20% of production, generates economic, social and environmental problems. The objectives of this work were to evaluate the antioxidant, antifungal and antibacterial activity of green and roasted coffee extracts. Extracts were prepared from green and roasted coffee beans using the solid-liquid reflux extraction technique, using ethanol as a solvent. The antioxidant potential was evaluated by the 2,2-diphenyl-1-picrylhydrazyl radical stabilization method (DPPH). The evaluation of the fungal inhibition potential of the extracts was performed by analysis of mycelial growth and scanning electron microscopy (SEM) of Aspergillus westerdijkiae and Aspergillus carbonarius species. The antibacterial activity was determined by the microdilution method, evaluating the MIC and MIB of the extracts under the species Salmonella enterica Choleraesuis and Listeria monocytogenes, and subsequently analyzed by SEM. The green coffee extract was the most efficient in inhibiting the DPPH radical, and the roasted coffee extract did not show antioxidant activity at the tested concentrations. Statistical data differed for the extracts regarding the antifungal potential, but the green coffee extract was more efficient in inhibiting mycelial growth. The species A. carbonarius was more sensitive to the extracts than A. westerdijkiae, being completely inhibited at a concentration of 0.42 g mL-1 by the green coffee extract. Both coffee extracts did not show bactericidal activity, and the roasted coffee extract also did not show a bacteriostatic effect. The minimum inhibitory concentration (MIC) of green coffee extract for L. monocytogenes and S. Choleraesuis was related to the concentration 0.21 g mL-1. It was concluded that the ethanolic extract of green coffee was the one that presented the highest antioxidant, antifungal and antibacterial activity, presenting high potential as a by-product for the industry.