Studies On Selection Of New Solvent And Oil Extraction Technology From Cold-Pressed Meal Of Rapeseed With Mixture Solvent

Rapeseed is an important source of oil and protein with high quality, the efficient processing and utilization of which is based on the advanced extraction of fat and oil. Now, the technologies of dehulling and cold-pressing of rapeseed have become the trend of the development of extraction oil. The cake of rapeseed cold-pressed and dehulled contains 15%～20% oil, which integrates with protein and must be extracted with solvent. Extracting capabilities and physical properties of solvent were vital to oil quality. Currently, n-hexane was restricted in the usesage in industry because of its environmental and health hazards. In addition, n-hexane is from petroleum and un-renewable resource. The research and development of new solvent became the focus in oil-processing industry, in which the renewable resources and the mixture solvent are new research direction worldwide.In this study, the dehulled and cold-pressed cake of rapeseed was used as materials to select oil extracting solvents, and the selected solvent was safer than n-hexane. The extraction conditions of the new mixture solvents were determined and optimized by the response surface. The procedure of extracting and seperating oil and crude phospholipids from the cake of rapeseed dehulled and cold-pressed was primarily evaluated. The following results were obtained.1 Study on selection of new mixture solventThe effects of methanol, ethanol, isopropanol, acetone, ethyl acetate, ligroin and hexane on the residual oil rate, phospholipids' content in the extracted oil and the quality of extracted oil were compared using the cake of dehulled and cold-pressed rapeseed. Results indicated that the lower residual oil rate was observed in the treatment with ethyl acetate and the lowest phospholipids' content and high quality were also found in the treatment with acetone. To improve the extracting capability of acetone and decrease the phospholipids' contents in oil extracted with ethyl acetate, the mixture solvent of acetone and ethyl ester was selected to extract oil from the cake of dehulled and cold-pressed rapeseed considering the physical parameters, safety and origin of acetone and ethyl acetate.2 Study on the extraction conditions with new mixture solventAcetone/ethyl acetate mixture solvents were adopted to extract oil and phospholipids from the cake of dehulled and cold-pressed rapeseed at the same time. Using the residual oil and phospholipids' contents respectively as analysis indice, the extraction conditions were established by the response surface method. The optimum conditions of extraction established were that the mixture solvent-material ratio was 7, the optimum ratio of acetone-ethyl acetate was 2.7, the optimum temperature was about 25℃and the extraction time was 2.6h. The multi-level counter-flow liquid-solid extraction experiment was carried out on the basis of optimized scheme. The results showed, the mixture solvent-material ratio decreased to 2.93 and the residual oil rate of rapeseed cake decreased to 0.92%. The quality of extracted oil reached national band 4 standard (GB1536).3 Primary studies on the technology of extraction oil from cold-pressing cake of rapeseed with mixture solventTo consider four working procedures of lixiviation, wet meal desolvation, phospholipids' isolation and the mixture solvent recovery, the suggestions were that extraction technology adopted soak-percolation method; the technology of wet meal desolvention adopted a centrifugal separation and evaporation method; Crude phospholipids were isolated by centrifugal sedimentation separation of hydrocyclone, and the mixture solvent was recovered with vacuum evaporation. This technology could decrease solvent usage reasonably, reduce consumption of energy and solvent and enhance the use efficiency.