Study On Extraction Of Residual Oil And Preparation Of Compound Amino Acid In Tung Meal

Tung oil trees are the economic forest tree of China and their have a long history of cultivation. Tung oil, which is the main products of tung oil tree, is an important industrial oil. At the same, it is China’s traditional bulk export commodities. Tung oil, which has fast drying, good gloss, heat, acid, alkali, non-conductive and other excellent features, is widely used. With the increasing of social demand, the tung oil processing capacity is also increased, which results in a large number of tung meal and tung shell. Tung meal contains many materials, such as residual tung oil, crude protein, total sugar, starch and so on. But, it is only used as fertilizer owing to possessing a certain toxic. Tung shell is used as fuel and their added value are very low. Therefore, how to increase the added value of tung meal and tung shell, turn waste into treasure and develop their new uses become a key scientific issues. In such cases, the extraction of residual oil and compound amino acid in tung meal are proposed. The main contents are as follows:(1) The extraction of residual oil in tung meal. The extraction of residual tung oil was achieved by maceration extraction (ME), microwave-assisted extraction (MAE) and ultrasonic-assisted extraction (UAE) using tung meal as raw material. The effects of some operating parameters such as extraction time, extraction temperature, ultrasonic power and solvent to solid ratio on the extraction yield of residual oil were investigated. The optimum conditions of extraction process was obtained by response surface method; the structure of tung meal was characterized by scanning electron microscopy; the fatty acid compositions of residual oil were analyzed by GC-MS; the structure of the residual oil was characterized by FT-IR. The results showed that:UAE was superior to MAE and ME; the optimal UAE condition was obtained with the temperature of 25 ℃, extraction time of 37 min, ultrasonic power of 160 W and solvent to solid ratio of 3:1 (mL/g) and extraction yield was 6.30%; SEM results indicated that UAE had different structure of tung meal compared to other methods and solid particle surface showed the state of fragmentation; FT-IR results showed that the spectrums of three extraction methods had a little difference and the compositions of the residual oils were not affected significantly by the application of ultrasound; GC-MS results showed that the compositions of the residual oils obtained by the three extraction methods were the same. It had been shown that the compositions of the tung oil were not affected significantly by the application of ultrasound.(2) The preparation of compound amimo acid in tung meal. The preparation of amino acid was achieved by conventional method (CM) and ultrasonic-assisted extraction (UAE) using tung meal as raw material. The effects of some operating parameters such as time, temperature, ultrasonic power, solvent to solid ratio and acid concentration on the conversion rate of amino nitrogen had been investigated and the optimum conditions for the extraction process was obtained by orthogonal experiments. Besides, amino acid compositions of the amino acid hydrolysis were analyzed by automatic amino acid analyzer. The results showed that:UAE was superior to CM; the optimum condition to prepare compound amino acid by UAE was:time of 4 h, temperature of 65 ℃, ultrasonic power of 225 W and acid concentrate of 4 mol/L. The results from the analysis of variance showed that the time on the ammonia nitrogen conversion rate was significant. Free amino acid composition of conventional extraction and ultrasonic-assisted extraction were the same. It had been shown that the compositions of free amino acid were not affected significantly by the application of ultrasound.