Drying of medicinal and aromatic leaves: analysis of drying process

Abstract

A considerable amount of dried herbs for supplying of pharmaceutical and food industries in Brazil is concentrated in local producers, who handle and process the materials based mainly on empirical techniques. Low quality of dried products, as well as irregular and seasonal production, are recurrent complaints of industry and final consumers. The crescent demand for fresh herbs and their increasing economic relevance recommend urgent incorporation of technological advances in the production chain, with standardization of processing procedures and methodologies, development and optimization of adequate equipment for drying, determination of relevant physical/thermodynamic/transport properties, and analysis of how the active principles of a plant are affected by the conditions of processing and storage. This research is focused on investigating the drying of fresh leaves and storage of dried materials, aiming to evaluate how these operations affect the composition and active principles of the fresh herbs. Two species were chosen for this study based on their potential applications in pharmaceutical/cosmetic or food industries, which are the peruvian pepper tree (Schinus molle) and basil (Ocimum basilicum L.). The drying will be performed in convective oven and in vibrated beds with aeration, varying the ranges of temperature, air velocity and vibration parameters (frequency and amplitude of vibration). The processes will be evaluated based on the reduction of moisture content, visual aspect (color and shape), and preservation of interest compounds. Aiming a fundamental analysis and better comprehension of drying mechanisms, thin-layer kinetic data will be obtained and fitted to classical models available in the literature. Also, a mathematical modeling of drying process in vibrated beds will be applied. A detailed characterization of physical and thermal properties will be carried out, as they are necessary as input data for modeling. This characterization includes the measurement of dimensions, shape factors, specific mass, thermal properties (specific heat and thermal conductivity), and equilibrium moisture content. Finally, the preservation of active principles and moisture content will be evaluated for storage under controlled conditions of relative moisture and temperature. (AU)