Cristalização da cafeína extraída da casca do café

Abstract

Brazil is the largest producer, consumer and exporter of Arabica coffee in the world. The increase of the residue generated after grain processing is proportional to the increase in coffee production, that is, the ratio between the obtained grain and the coffee husk is 1:1 (m/m). Since a high volume of residue is generated during the processing of the grain coffee, research is necessary for its destination. From the foregoing context, the present work has as general objective to elaborate a technology for the use of this residue by crystallization of the caffeine extracted from the coffee husks of the Coffea arabica specie, red catuaí variety. In order to reach the proposed objective, a central composite planning for the roasting phase was carried out in order to optimize the extraction process, finding the optimum condition to extract greater amounts of caffeine, in comparison with the value obtained in practice. The obtained temperature and time data, within the analyzed range of these variables were 147.6°C and 5.3 min, respectively, and corresponded to the maximum caffeine content extracted from 54.3% (m / m). In practice, 43.08% of the total caffeine was extracted in an optimized condition. In order to direct the study of the crystallization of extracted caffeine the solubility of caffeine in water at temperatures ranging from 10 to 60°C and the crystallization of commercial caffeine were investigated. A central composite planning was carried out, using commercial caffeine for the preparation of solutions and seeds. This allowed a study of the significant variables in the operation, construction of a response prediction model, analysis of response surfaces and selection of an optimum operating point within the specified experimental range and for the percentage increase mass response. The average yield was 285.6%. The caffeine crystallization of the coffee husk was carried out under similar conditions to the optimization performed in the central composite planning with seeds obtained by cooling. The responses indicated crystalline growth of the added seeds, even in the presence of impurities and possible crystallization inhibitors. Crystallization was decisive in the purification of the caffeine extracted from the coffee husks, reaching a purity of about 88%.