Study On The Kinetics Of Rapeseed Liquid-Liquid-Solid Extraction

Two-liquid phase solvent extraction technology is a novel method. Two improved products, a proteinaceous meal with reduced glucosinolates and a high quality triglyceride oil, both acceptable as feed and food ingredients could be yielded by the process. The meals were free-flowing, light in color, bland in taste and rich in proteins. Two-liquid phase solvent extraction technology has been developed since 1980's and many achievements were acquired in the labs, but there were some troubles in the industrialization. In this paper, the kinetics of extracting both of oil and glucosinolates from rapeseed particles with two-liquid phase solvent system was studied. Valuable data of the mass transfer through a serial of experiments were obtained. A mass transfer model was set up to describe the extraction process. The diffusion coefficients of the rapeseed oil and glucosinolates within rapeseed particles, which would be useful in the scale up of the process, could be calculated by the model. During the periods to finish the experimental tasks, following as main items were done. (1) The method to determine the glucosinolates in rapeseed meal extracted by two-liquid phase solvent system was improved. Palladium test was proved to be suitable for detection the total glucosinolates in rapeseed meal. Both wavelengths of 450nm and 540nm were test and found that detection with 450nm would gaine a minor mean error. Further more, some standard meal which the glucosinoates concentration were 13.3～110.3μmol/g detected by HPLC were selected and used to set up the standard curve. Finally, a mean error of 6μmol/g was obtained and used to determine the glucosinolates with the wavelength of 450nm. (2) The distribution of particle size of the ground rapeseed was determined. The mesh analysis was completed for the rapeseed particles, which were ground in 30, 60, 90, and 180s and the nominal diameters of these ground rapeseed were 0.755, 0.499, 0.424 and 0.326 mm. (3) Many factors influencing the extracting rate in two-liquid phase solvent extraction were studied. It was concluded that minor rapeseed diameter, higher temperature and hexane ratio were benefit for the rapeseed oil extraction. Also minor rapeseed diameter, highertemperature, higher hexane ratio and methanol ratio were benefit for the glucosinolates extraction.(4) A model as follows based on differential mass balances performed along the radial of the isotropic rapeseed particle was proposed: Regression for the parameters of the model using the rapeseed oil and glucosino- lates extraction rate data was completed. At last, the diffusion coefficient of the extraction process was obtained and their order of magnitude was 10－13 m2/s.(5) The relationship between the diffusion coefficient and temperature could be expressed by Arrhenius law and the activation energy of the extraction process was calculated.