Padronização do processo de secagem e de extração de óleos essenciais em subprodutos de hortelã (Mentha spp)

Abstract

Waste generated in the food industry can be a source of raw material for the extraction of bioactive compounds, avoiding disposal and obtaining a product with greater added value. Therefore, the aim of the study was to determine the conditions for drying and extracting volatile substances from mint by-products. Starting with the drying kinetics of mint residue at different temperatures, using the mathematical models of Page, Verna, Diffusion approximation, Wang and Singh, Two terms, Logarithmic, Lewis, Henderson and Pabis, Modified Henderson and Pabis and Modified Page, to the adjustment of the experimental and evaluated data according to the coefficients of determination (R2) and mean squared deviation (DQM). The drying kinetics was performed in triplicate in a dehydrator with air circulation at an average speed of 0.5 m/s, at temperatures of 50°C, 60°C and 70°C, for determined times until constant mass. The non-linear regression analysis, using the Quasi Newton method, was carried out using the Statistica 8.0 program, where the parameter values of the mathematical models were estimated as a function of the drying air temperature. In all process conditions, the mathematical models tested to the experimental data showed satisfactory adjustments to the drying kinetics data, with emphasis on the models of Page, Wang and Singh, Modified Page and Diffusion Approximation, for presenting better statistical coefficients to describe the drying kinetics of mint residue, with R2 > 0.99 and DQM < 0.03. It was observed that increasing the temperature of the drying air reduced the drying time to reach its thermodynamic equilibrium and the final water content of the product. As for the extraction of volatile substances, this was carried out in a semi-industrial essential oil distiller by hydrodistillation and a Clevenger type apparatus, in order to compare the two extraction methods. The material extracted from the hydrodistillation did not present phase separation, obtaining an aromatic hydrolate, which was analyzed by gas chromatography with chemical components similar to those of the essential oil of mint leaves, with menthol standing out as the major component.