Production of dry extracts of medicinal Brazilian plants by spouted bed process: Development of the process and evaluation of thermal degradation during the drying operation

The aim of this research was to develop a method for the preparation of dryed extracts of medicinal Brazilian plants, using the spouted bed process as the drying equipment. The first step was the development of the extraction procedure. A 3 x 2 factorial design was used to study the effect of the ratio between the plant and solvent mass, the ratio between the water and ethanol mass, and the extraction time. The components were weighed and placed in a shaker at a temperature of 30 degreesC. Next, the extracts were filtered and concentrated three times in a rotary evaporator. Samples of the concentrated extracts were put in an oven, in order to determinate the solids concentration, and chemically analysed for the determination of the total flavonoid content, which was used as an indicator of quality of the extraction. The variation of the product size distribution, product moisture content, flavonoid degradation ratio (relative to the concentrated extract), product recovery and process thermal efficiency, were measured as a function of the inlet temperature of the spouting gas and of the feed mass flow rate of concentrated extract. HPLC-DAD analyses were carried-out to verify the occurence of alteration of chromatographic profiles during the drying the operation. The main conclusions of this work were: (i) an increase in the drying temperature together with low feed flow rate of hydro-alcoholic extracts, in general, tends to increase the degradation of flavonoid compounds; (ii) no alteration of the chromatographic profiles was observed as consequence of drying.