High pressure CO2 extraction. Fundamentals and applications in the food industry

Supercritical extraction (SFE) is a unit operation that exploits the dissol ving power of supercritical fluids (SF) under conditions above their critic al temperature and pressure. It is possible to obtain solvent-free extracts using SF and the extraction is faster than using conventional organic solv ents. These advantages are due to the high volatility of SF (gases under no rmal environmental conditions) and improved transport properties (i.e., hig h diffusivity and low viscosity). When using carbon dioxide (CO2) in partic ular, moderate-temperature processing and high selectivity towards valuable microconstituents in natural products can be achieved. This article presen ts a review of transport properties and solubilities in SF, particularly CO 2, as well as other underlying factors that are responsible for the kinetic s and phase equilibrium in SFE processes. It also describes the selective C O2 extraction of essential oils, pungent principles, carotenoid pigments, a ntioxidants, antimicrobials, and related substances to be used as ingredien ts for the food, drug and perfume industries, from spices, herbs and other plant materials. These very important applications are discussed from the p oint of view of the potential applications of SFE in Latin America. The two most: important commercial applications of SFE in the food industry, namel y hop extraction and coffee decaffeination, are reviewed to a limited exten t. Some other potential applications briefly described include extraction a nd fractionation of edible fats and oils, purification of solid matrices, a nd concentration of fermentation broths, fruit juices and other extracts. I n most cases CO2 extracts are compared with counterparts obtained using con ventional methods.