Extraction, Purification And Stability Of Soybean Lecithin

Lecithin, as a kind of important physiological activator and natural surface active agent, offers many advantages to health, and is widely used in the fields of food, pharmacy and cosmetic. So, there is ever-growing marketing tendency in producing more and more pure lecithin.Soybean, an abundant plant resource in the world, is grown over 100 million ton every year in which 15 million ton is from China. It is much cheaper to produce lecithin by soybean than egg yolk. Moreover, soybean lecithin consists of more than 20% phosphatidyl cholines. It's clear that use of soybean as lecithin material to extract phosphatidyl cholines finds a new way to obtain this functional substance. Traditionally, solvent extraction is one of main methods for obtaining pure lecithin. One of disadvantages in employing the method to extract lecithin is that noxious solvent usually resides in end-products and leads to un-safety. Supercritical carbon dioxide (SC-CO2) extraction shows many advantages as a new tool over traditional technologies in the separation of lecithin, including non-pollution, lower reaction temperature, specific and simpler processing. So, the objectives of this present study were to: (1) establish an apparent SC-CO₂ based procedure to purify phosphatidyl cholines from soybean;and (2) investigate the stability of purified phosphatidyl cholines against various stresses.Soybean oil was firstly removed from soybean flour as raw material using supercritical CO2. Soybean cake remained was used to extract phosphatidyl cholines in the next experiments. The orthogonal design L9(34) showed that extraction pressure, extraction temperature, extraction time were main factors affecting the remove of soybean oil. Theoptimum extraction pressure, temperature and time was 25 Mpa, 40°C and 90min respectively. Removed oil from soybean reached 18.34% with the combination of the optimal parameters. The analysis of the physical and chemical properties of the soybean oil showed that the quality of soybean oil extracted by supercritical CO2 was super to that recommended by national standard GB1535-2003.Four factors quadratic rotating design was used to optimize the parameters of supercritical CO2 in the extraction of soybean lecithin from soybean cake to acquire the high purity lecithin. The influence of pressure, temperature, time and ethanol content on the extraction ratio and purity of lecithin was studied. Clearly, ethanol was the most important factor in yielding the higher purity of lecithin, followed by temperature, time and pressure. A significant synergy was found between temperature and ethanol content (P<0.05) in controlling the purity of lecithin. The optimum extraction conditions of lecithin were 40 MPa, 40°C, 150 min and 20% ethanol. The ratio and purity of lecithin extracted by supercritical CO2 was 93% and 78.24 %, respectively.HPLC procedure was established to analyze lecithin extracted from soybean cake. HPLC working procedure included mobile phase with methanol:2-propanol: n-hexane(60/35/5,V/V), and lecithin retention time with 26.035 min.Lecithin product extracted by supercritical CO2 was stored for its stability. It was seen that addition of antioxidant to lecithin product produced no positive function in stopping lecithin from oxidation. It was proved that vacuumed packaging in combination with refrigerated storage improved the stability of lecithin product extracted.The final lecithin product obtained based on the use of our technology would be promising in the applications of food and pharmacy due to non-pollution and safety. Our work either gave technological advantage in the purification of high purity phosphatidyl cholines or the extraction of natural products.