ANTIOXIDANT ACTIVITY AND TOTAL PHENOLIC CONTENT OF AMAZONIAN ROBUSTA COFFEE HUSK: THE INFLUENCE OF SELF- INDUCED ANAEROBIOSIS FERMENTATION

The coffee husk is a byproduct of the coffee industry that has been generating interest in the domestic market due to its bioactive potential. The fermentation process induces changes in sensory characteristics, opening opportunities to produce new products and fostering a sustainable and economically viable industry. Despite its significance, coffee husk has been relatively underexplored. The aim of this present study was to determine the total phenolic compound content (by Folin-Ciocalteu method) and antioxidant activity (by FRAP, DPPH, ABTS, and ORAC assay) of coffee husks subjected to natural drying and a self-induced anaerobiosis fermentation process for 10 days. For the experiment, were used Amazonian Robusta coffee husks (Coffea canephora L.) supplied by EMBRAPA-RO. Aqueous extracts were prepared from the samples, using water at 80°C for 30min at 10% (m/v). The results showed that the fermented husks exhibited lower total phenolic values compared to the natural husk (70.22±1.45 mg GAE/g; p<0.001). However, during the fermentation process, it was observed that the phenolic content progressively decreased until the 4th day of fermentation (2th day=64.87±0.57 mg GAE/g; 4th day=28.32±0.17 mg GAE/g, respectively), and subsequently, on the 6th day, there was an increase in total phenolic content (46.74±3.96 mg GAE/g), followed by a progressive decline until the 10th day (27.21±0.37 mg GAE/g). In assays related to antioxidant activity, a similar pattern was observed in the samples, with natural coffee husk (FRAP:0.37±0.01 μmol Fe2SO4/mL; DPPH: 1293.3±38.2 μmol TE/g; ABTS+:5956.7±98.7 μmol TE/g and ORAC:69.71±8.94 μmol TE/g) exhibiting a greater reducing power compared to the fermented husks (p<0.05). In conclusion, the results suggest that fermentation reduced the antioxidant potential of the coffee husk, confirmed by the degradation of phenolic compounds during the process, possibly enhanced by the low pH, a consequence of the production of organic acids during fermentation.