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The effect of molecular structure and operating conditions on the solubility of triglycerides in supercritical CO₂ Cheok, Nai Tin


In order to assess the feasibility of using supercritical fluid as a solvent for oil extraction in the oil and fat industry, basic information is required on oil solubility as a function of various system parameters. Such information would be useful in the design of extraction systems. This research work studied the effects of temperature and pressure on the equilibrium solubilities of triglycerides in supercritical carbon dioxide which is considered one of the best solvents for supercritical fluid extraction. A series of experiments was carried out using a modified liquid chromatograph. Samples tested included pure simple triglycerides that are saturated and unsaturated, and triglyceride mixtures. Extraction experiments were extended to cocoa butter, palm kernel oil and their mixtures with various weight, ratios. The effect of sample water content on the oil solubility was investigated using cocoa butter/water mixtures in different proportions. The solubilities of simple triglycerides were found to depend strongly on pressure and temperature. Triglycerides with a longer carbon chain (C18) exhibit lower solubilities over the range of temperatures and pressures studied. Unsaturated triglycerides were more soluble than their saturated counterparts. Furthermore, for the saturated triglycerides, the solubilities varied inversely as their molecular weights. Significant fractionation occured during the extraction of simple triglyceride mixtures at 36 MPa and 55 °C. Results of tests on cocoa butter and palm kernel oil separately indicated that no fractionation had taken place during the extraction process. However, significant fractionation was again observed when the two oils were mixed. Sample water content up to 50% by weight had negligible effect on the oil extractability and its equilibrium solubility in CO₂.

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