Supercritical Carbon Dioxide Extraction Of Grape Seed Oil

Supercritical carbon dioxide extraction technology is a new chemical engineering separation technique, which has been well developed since the 1970s'. Owing to its several advantages, such as strong solubility and selectivity, high mass-transfer rate, mild operation conditions, friendly to environment and high efficiency, Supercritical carbon dioxide extraction technology has gained more and more applications in food industry, natural perfume, Chinese traditional herbal medicine, polymer material and environment protection etc.Grape seed contains 14%-18% oil by weight. Grape seed oil is rich in unsaturated fatty acids, among which linoleic acid is more than 70% in content. Further more, Vitamin E and some trace elements essential to human bodies are also abundant in grape seed. In China, most of the grape seed is used as feed or discarded as industrial waste and thus will cause pollution to the environment if not treated properly. The conventional ways to produce grape seed oil are mechanical method and solvent method. Normally, low yield, labor-intensive and remnant of organic solvent are the main problems with conventional ways. It is therefore both economically and socially beneficial to develop a new method to produce grape seed oil. The extraction of grape seed oil with supercritical carbon dioxide is investigated in these researches.Firstly, the single factor experiment was carried out to find the effects of particle size, pressure, temperature and extraction time on oil yields. It was shown that the yields of grape seed oil get higher first and then lower with the decrease of the particle sizes; the yields almost increase linearly with the increase of the pressure; the effects of temperature are complicated since the oil yields increase with the increase of temperature when pressure is less than a specific value. However, when pressure is more than the value, the effects on yields are negative; the yields always increase while prolonging the extraction time. However, take account of the viewpoint of economics, the best extraction time should not exceed the time cost for the process to get balanced.Based on the results of single factor experiment, pressure, temperature and extraction time were selected as influencing factors to arrange orthogonal experiment. The obtained optimal operation conditions are: pressure 50MPa,temperature 32℃and extraction time 60min. The effects of pressure and extraction time are significant on oil yields. The repeatability of the obtained best condition is satisfactory.Oil extracted by both supercritical carbon dioxide and organic solvent was tested and analyzed. The results showed that the oil by supercritical method is better than solvent method in all indexes and also in accordance with national standards. Therefore, the best operational conditions are applicable.The mass-transfer mechanism was also discussed. Based on the literature reports and the analysis of experimental data, a three-step mass-transfer process was proposed. By analyzing the mechanism of mass-transfer between the supercritical fluid phase and solid phase, the process can be mathematically simulated and lay a foundation to the industrialization of supercritical carbon dioxide extraction technology of grape seed oil.