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Supercritical fluid extraction of canola seed Fattori, Michael J.


The extraction of oil from fixed beds of Canola seed ( Brassica napus and Brassica campestris ) was studied using carbon dioxide at temperatures and pressures ranging from 25 to 90°C and 10-36 MPa respectively. The highest oil solubility in the CO₂ (11 mg/g CO₂) was observed at 36 MPa and 55°C. The equilibrium oil concentration in the CO₂ phase, was found to be independent of the oil concentration in the seed phase. The extracts were found to be essentially free from phosphorus (<7ppm) and their fatty acid content did not change significantly as the extraction progressed. The total amount of oil recovered from the seeds by CO₂ extraction depended upon the seed pre-treatment. For commercially flaked seed, this amount was comparable to that recoverable by conventional hexane extraction. The CO₂ extraction of simple triglycerides at 36 MPa and 55°C was investigated. The solubilities of tripalmitolein, triolein, and trieicosenoin were 20 mg/g CO₂, 10 mg/g CO₂, and 4 mg/g CO₂ respectively. The composition of CO₂ extracts of an equimolar mixture of the above triglycerides was also studied. It was found that the concentration of each triglyceride in the extract was equal to the product of its mole-fraction in the mixture and its solubility in the CO₂. Equations governing the mass transfer from the Canola seed to the CO₂ solvent were developed. A transient one-dimensional mathematical model based on these equations was used to obtain concentration profiles of oil in both the solvent and seed phases, and to determine the overall volumetric mass transfer coefficient. The calculated concentrations and extraction rates were in good agreement with experimental results. The overall volumetric mass transfer coefficient for the initial constant rate period was found to be proportional to the 0.54 power of interstitial velocity.

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