Tilapia Fish Scales Extraction Process Lecithin

In the last decade, tilapia aquaculture production grew fast. FAO data shows that global annual production of tilapia aquaculture in 2010 is close to 3.4 million tons, and the tilapia aquaculture production in China is 1.332 million tons which accounts for 39.2% of global production. At present, China is the largest country in the tilapia breeding industry in the world scale and Chinese production accounts for more than 50% of the worldwide output. Tilapia scales are by-products from tilapia processing, accounted for about 2% ~ 5% of the total body quality. Tilapia scales are rich in lecithin, protein and other nutrients which are necessary for human. The weight of lecithin accounts for about 2% ~ 3% of the weight of fish scale.In this research, tilapia scales are used as raw material. Firstly, they were washed, dried, crushed, soaked in acetone to remove impurity. Secondly, microwave assisted extraction was carried out to extract lecithin in scales. Thirdly, the as-obtained raw lecithin was preliminarily purified through crystallization for further separation and purification. Finally, lecithin was purified by membrane processing to obtain pure product.1. Pretreatment stage for raw material.This stage can be divided into physical and chemical processing. In physical processing, Tilapia scales were cleaned, dried and crushed. In chemical processing, the scales was soaked in acetone to remove cholesterol, fat and other impurities in the scales, and then the pre-treated scales were extracted in ethanol according to the nature of lecithin.2. Microwave assisted extraction phase.The extraction rate of lecithin is used as index to evaluate the effect of extracting conditions and optimize the extraction process through orthogonal test. The experimental results showed that the optimal conditions were microwave power 300 W, time 6 min, material-water ratio 1:20 and ethanol volume fraction 95%. Under the optimal conditions, lecithin yield reached 2.67%. The influence factors were in the order of extraction time, microwave power, material-water ratio and ethanol volume fraction.3. Crystallization purification stage.Lecithin extraction was crystallization purified to evaluate the effect of single factors on extraction efficiency. The extraction process was optimized by orthogonal experiment and the results showed that the optimal conditions were material-water ratio 25 m L/g, time 12 h and temperature-10 ℃. Under the optimal conditions, the purity of lecithin reached 63.8%. Lecithin can be better purified in this method and the affecting factors were in the order of temperature, material-water ratio and time.4. Membrane treatment and recrystallization stage.The experimental results showed that the ceramic membrane with pore size 20 nm had the best separation effect for lecithin. The ceramic membrane with pore size 20 nm was adopted to treat crude extraction from lecithin. The effect of temperature, solvent and material-water ratio on the purity of lecithin was studied, and the results demonstrated that the separating effect of the ceramic membrane was the highest under the conditions of solvent ethanol, material-water ratio 1:20 and temperature 20 ℃. The purity of lecithin reached 90.04% under these conditions and can be reached 93.32% after further purification.