SUPERCRITICAL FLUID EXTRACTION OF MALAGUETA PEPPER (Capsicum frutescens L.) ASSISTED BY ULTRASOUND – EFFECTS ON VEGETABLE STRUCTURE

In a supercritical fluid extraction (SFE) unit, one generally can change the temperature, pressure, extraction bed size, solvent flow rate, among others, in order to maximize the global yield. The morphology of the solid substrate particle can also influence the extraction efficiency, since the solvent must cross diffusive paths inside the solid particle, in order to extract specific compounds Moreover, the SFE process capacity may be improved by using combined extraction techniques, such as the use of different co-solvents and ultrasonic waves. The ultrasonic technology is based on the high frequency ultrasonic waves, which are capable of causing cavitations and disrupting the cell walls of vegetable materials. This favors the penetration of solvent and mass transfer, increasing the extraction yield and velocity. The objective of this study was to obtain extracts of malagueta pepper (Capsicum frutescens L.) using SFE assisted by ultrasound and conventional extraction method, and understand the effects of extraction on the structure of the vegetable matrix. The raw material used was malagueta pepper dried at 50 °C (5% w. b.) and triturated. The SFE conditions were 40 ± 3 °C and 15 ± 0.5 MPa. The CO2 mass flow rate was fixed at 0.5 ± 0.1 kg/h. To study the influence of extraction on vegetable structure, SFE extractions were performed without ultrasound and with ultrasound at powers of 280 and 360 W. Conventional extractions (soxhlet) were carried out using n-hexane as solvent. The microstructures of the pepper pericarp samples were analyzed before and after the extractions using a scanning electron microscope equipped with a field emission gun (FESEM FEI Quanta 650). The results showed that SFE assisted by ultrasound increased global yield when compared to the SFE without ultrasound. The highest yield was obtained in the conventional method (soxhlet). Images obtained by FESEM showed that the action of ultrasound waves did not cause cracks on the cell wall surface, but the images reveal morphological changes caused by disturbances on the vegetal matrix due to application of the ultrasound.