Study On Filtration To Produce Powdery Lecithin By Membrane

In view of domestic lecithin processing situation, the method to produce food grade concentrated lecithin and powdery lecithin through the way of membrane filtration was obtained using feed grade condensed lecithin as raw material. The preparation technology of powdery lecithin was focused on in the study. The main contents in this thesis are:The effect of some factors to the size of lecithin reverse micelle in the food grade condensed lecithin—hexane system was studied by using dynamic light scattering technology. It was found that the ratio of lecithin to hexane, the content of water and temperature had a significant influence on the size of reverse micelle. With increasing the content of water, the size of lecithin reverse micelle had a obvious trend of increasing firstly and then decreased. While the content of water was 9%, the size became maximum that the average size was up to 10nm. The reverse micelle size increased as the ratio of hexane to lecithin decreasing and temperature lowering, but the effect in changing the size was in small quantity compared to adding water.Lecithin-hexane solution was microfiltrated by the inorganic ceramic membrane. Through this process, food grade concentrated lecithin with few impurities and good diaphanous was produced. The relationships between membrane flux and the size of membrane aperture, trans-membrane pressure, the ratio of solution and temperature were investigated. At the same time, the effects of the size of aperture, solution ratio and operating temperature on the content of acetone insoluble matter and hexane insoluble matter were also studied. At 45℃, the filtration pressure of 0.20MPa, the solution which mass ratio of lecithin to hexane was 1:3 was microfiltrated by membrane with aperture of 0.6μm, the flux was 193L/(m2.h) and the content of acetone insoluble matter and hexane insoluble matter reached to 60.20% and 0.0082% respectively. Under appropriate conditions, food grade condensed lecithin could achieved the aim of deoiling by ultrafiltration with inorganic ceramic membrane. The results showed that the ratio of solution, the size of membrane aperture, water content, temperature, pressure and the way of operation were the main factors affecting the membrane flux and the content of acetone insoluble matter. Through single factor test, the optimal experiment conditions were achieved by orthogonal experiment. At 45℃, the filtration pressure of 0.20MPa, the solution (mass ratio of lecithin to hexane was 1:3, the content of water was 9%) was ultrafiltrated by membrane with aperture of 5nm under the circumstance of continuous solvent supplement, the flux was 38.4L/(m2.h) and the content of acetone insoluble matter reached to 97.22%. Other primary index was also fulfilled the requirement of foreign enterprise's standard.Comparing with the traditional membrane cleaning methods, it was showed that ultrasonic auxiliary cleaning had a better result. Experiment showed that after cleaned 15min using ultrasonic, the membrane was then cleaned by 1% sodium hydroxide solution, the water flux recovery coefficient could be 99.1%. It could effectively enable membrane regeneration.