Extração de cafeína e compostos com atividade antioxidante das folhas de erva-mate por três processos de extração : infusão, campo elétrico moderado e fluido supercrítico

Abstract

The industrial processing of the yerba mate undergoes it at high temperatures in order to conserve it and confer flavor and aroma. One step in this process is called bleaching, which has the purpose of inactivating oxidative enzymes present in leaves of yerba mate. To evaluate the effect of this step to obtaining caffeine and antioxidant compounds, extractions were performed by aqueous infusion at 30, 60 and 90 ° C and extractions by moderate electric field at 0, 25 and 180 V. The results showed that a higher amount of caffeine was obtained for both extraction methods before the bleaching process. In turn, the compounds that have antioxidant activity were obtained in greater amount after bleaching. This behavioral difference may be explained by changes in plant cell structure observed by transmission electron microscopy. In order to obtain a decaffeinated yerba mate, supercritical fluid extraction with carbon dioxide as solvent and ethanol as modifier was chosen. Experiments were performed in three steps that evaluated the following process variables: solvent flow rate, modifier flow rate and time. The optimization applied through experimental designs resulted in an extraction condition capable of obtaining yerba mate with 0.163% ± 0.058% caffeine concentration in 4.25 h of extraction. Experiments were also carried out to purify the extracts without using toxic solvents (only water and ethanol were used) and extracts of yerba mate with a caffeine concentration of up to 92.34% were obtained.