ABSTRACT
I. Introduction to Supercritical Fluids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 A. Supercritical Fluid Extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 B. Applications of Supercritical Fluid Extraction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 C. Other Supercritical Fluids Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168
II. Properties of Supercritical Fluids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 III. Particle Sizing using Supercritical Fluids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169
A. Rapid Expansion of the Supercritical Fluids Method . . . . . . . . . . . . . . . . . . . . . . . . . 170 B. Gas Antisolvent and Supercritical Antisolvent Methods . . . . . . . . . . . . . . . . . . . . . . 170 C. Aerosol Solvent Extraction System and Solution Enhanced Dispersion
by Supercritical Fluids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 D. Particles from Gas-Saturated Solutions-Suspensions . . . . . . . . . . . . . . . . . . . . . . . . . 171
IV. Formation of Particles with CO2 as a Precipitant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171 A. Precipitation of Casein from Milk Using CO2 — Batch Processing . . . . . . . . . 171
1. Particle Size Distribution Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172 2. Microstructure of CO2 Precipitated Casein. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
B. Precipitation of Casein from Milk Using CO2 — Continuous Processing . . . 174 1. Particle Size Distribution Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
C. Precipitation of Other Proteins Using CO2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176 V. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177
ENPO: “dk2963_c006” — 2005/3/21 — 18:22 — page 168 — #2
I. INTRODUCTION TO SUPERCRITICAL FLUIDS
A. Supercritical Fluid Extraction
Supercritical fluid extraction (SFE) is the most familiar of the supercritical processing methods currently used by the food processing industries. SFE is carried out using supercritical carbon dioxide (SCO2), the most common supercritical fluid (SF), as the solvent. SCO2 is an environmentally benign and nontoxic solvent that is easily handled and easy to obtain. Food grade CO2 is a by-product of corn wet-milling operations and other fermentation processes. In a SFE process, CO2 may be recycled and reused — with small amounts of makeup SCO2 added in each cycle — thereby lowering process operation costs relative to processes that use organic solvents. It is also nonflammable and does not leave solvent residue that can contaminate the food substrate or extract. Supercritical ethane and propane are also suitable solvents for SFE and preferable to SCO2 in some cases; however, their use in food processing is unlikely because of the difficulty in obtaining these solvents for food use and the great care that must be exercised in handling them because of their flammability.
