Biblioteca do Café
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Item Oxidative stability of biodiesel in the presence of leaves and fruit extracts(Universidade Federal do Ceará, 2025-05-09) Branco, Isadora Guilherme; Romagnoli, Erica Signori; Gonçales Filho, José; Mantovani, Ana Carolina Gomes; Borsato, DionisioThis research evaluated the efficiency of ethanolic extracts from yerba mate leaves (Ilex paraguariensis), coffee leaves (coffea arabica), and jambolan pulp (Syzygium cumini Lamarck) through the application of the simplex-centroid mixture design, the super modified simplex optimization algorithm, and the functions of desirability, using the induction period (IP) and the rate constant (k) of the biodiesel oxidation reaction at 110 °C as responses. Antioxidant activity was observed in all extracts, manifesting either by reducing the rate constant or extending the biodiesel induction period in comparison to the control sample. The mathematical models derived from the simplex-centroid design exhibited adjusted determination coefficients of 0.990 for the IP model and 0.960 for the k model. Analysis of variance indicated the significance of both models at the 5% significance level for IP and k, with p1 = 7.382 × 10−4 and p2 = 1.177 × 10−3, respectively. The lack of fit was not significant at the same level with p1 = 0.132 and p2 = 0.653, showing that they can be used for predictive purposes. The analysis of the response surface and optimization using the super modified simplex method revealed that higher proportions of coffee leaves extract in the mixture yielded superior IP values and lower k values.Item Young coffee leaves biotransformed by aspergillus oryzae in enriched source of caffeic acid(Editora UFLA, 2021) Hernández-Aguirre, Carlos; Mencía-Guevara, Alejandra; Rojas-Rojas, KatherineThis 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.