Microwave drying of yerba mate leaves: kinetics modeling and techno-economic analysis

Abstract

Ilex paraguariensis, known as yerba mate, is a native species from South America widely used in the preparation of drinks, with several bioactive compounds. Its industrial drying process is archaic and associated to the contamination of the leaves with carcinogenic compounds. Previous study reported microwave drying of yerba mate as a potential alternative for its drying, but there are no studies on the techno or economic aspects of this process. Hence, this study aims to determine the drying kinetics on the yerba mate leaves (YML) using the microwave assisted drying method, and to provide a techno-economics analysis for different production and rate of return of investment scenarios. Microwave drying (MWD) of yerba mate was conducted at different powers (675, 945, and 1,215 W), and conventional kinetics models were fitted to the experimental data. A techno-economics analysis was conducted considering the processing of 10 – 100 kg YML/h in an agribusiness located in South Brazil. As results, the different microwave powers resulted in different equilibrium moisture content, and only the MWD at 1,215 W achieved Brazilian’s legislation requirement of 10 % of moisture (wet basis). Page’s drying kinetics model presented the best fitting to the experimental data, and its parameters were used in the study of economic viability. Finally, a required selling price of 19.88 US$/kg was calculated for the selling of the dried YML, resulting in a time of return of investment of 1 year for an agribusiness processing 100 kg YML/h.