There is a need to increase vessel loads for high-pressure batch processes such as supercritical fluid extraction of solid substrates, but a precompacting treatment such as pelletization may negatively affect mass transfer rates. This work was aimed to quantify the effect of the microstructure of Jalapeno pepper pellets on the extraction rate and yield of oleoresins when using supercritical CO2 at 40°C and 320 bar as the solvent, so as to contribute with basic information that will help optimize pelletization treatments for solid substrates. Four types of substrates were obtained by considering 2 initial particle sizes and 2 initial moisture levels before pelletization, and the inner porosity and tortuosity of the resulting pellets were estimated. The internal mass transfer was favored in pellets showing a better distribution and connectedness of pores, and the extraction rate and yield improved when using pellets from flakes instead of milled flakes, with initial sample moisture exhibiting a more limited effect. A reduction in the particle size of the pellets improved mass transfer but caused a reduction in packing density, and these 2 factors had opposite effects on the "volumetric yield" of the process (mass of recovered solute per unit time and per unit volume of extraction vessel), which was also affected by prepelletizing sample conditioning. © 2005 Institute of Food Technologists.
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