Atividade antioxidante de extratos de café verde biotransformado pelo fungo Aspergillus oryzae

Abstract

Green coffee is known mainly for its antioxidant and antibacterial properties. Phenolic compounds such as chlorogenic acids, which are formed through hydroxycinnamic acids (caffeic, ferulic and other acids) linked to quinic acid, are present in large quantities in green coffee and have been recognized as natural antioxidants. However, hydroxycinnamic acids are found mainly in the esterified form with organic acids, sugars, lipids and are covalently bound to the cell wall, which reduces their bioavailability. Therefore, the objective of this study was to perform the biotransformation of the green coffee flour using the Aspergillus oryzae fungus aimed at increasing the antioxidant activity. The green coffee flour was fermented in solid state using the fungus Aspergillus oryzae (CCDCA102604) at 25 °C for 24, 48 and 72 hours and after fermentation the phenolic compounds were extracted using a hydroethanolic solution. The antioxidant activity of the extracts was evaluated by the DPPH• and reducing power methods, and the determination of total phenolic contents was performed using Folin-ciocateu method. Quantification of chlorogenic acid (5-ACQ), caffeic acid and caffeine in the extracts was also performed using high performance liquid chromatography. The results showed a significant increase of 115.7% and 66.4% of the antioxidant activity of the green coffee flour extracts fermented for 24 hours in relation to the unfermented coffee extract, measured by the DPPI-1• and reducing power methods, respectively. In addition, the fermentation process by the A. oryzae fungus for 24 hours also promoted a 68.6% increase in the content of phenolic compounds in relation to the unfermented extracts. The extracts fermented for 24 hours showed an increase in the content of chlorogenic acid and caffeic acid when compared to the non-biotransformed extracts. The increase in antioxidant activity was not observed in the extracts fermented for 48 and 72 hours. The results of this study showed the biotransformation process as a strategy to obtain an enriched extract of antioxidant compounds in their free forms with potential application in the food, supplementation and cosmetic industries.