Resumo:
This research focused on the study of young coffee leaves as a potential source of caffeic acid from the biotransformation of abundant chlorogenic acid. Aspergillus oryzae was isolated from koji rice and used for the solid-state fermentation of coffee leaves. The bioconversion of chlorogenic acid into caffeic acid was measured by HPLC-DAD. The water infusions of fermented coffee leaves were analyzed by sensory evaluation in comparison with unfermented coffee leaves as well as roasted coffee beans. The biotransformation of young coffee leaves yielded over 3.5-fold change increase of caffeic acid natural content in 87 hours, and equivalently, decreasing concentrations were observed for chlorogenic acids. Other bioactive compounds, such as mangiferin, rutin and caffeine, showed relatively minor changes. Sensory evaluation pointed out the effect of increasing caffeic acid-concentration on bitterness and astringency, which would have to be considered in the development and optimization of functional foods. As bitterness was increased by the enhanced caffeic acid concentrations, desirable flavor descriptors were also associated with fermented leaves, with the inclusion of notes traditionally associated with koji. This bioprocess proved to be highly efficient and could be implemented with relatively simple technology in-farm production systems.
