| Tung tree belongs to Euphorbiaceae Vernicia, which is a famous industrial oil tree. Tung oil is made by mechanical pressing or solvent extraction from tung tree seeds. Tung oil is a kind of high drying oil. Its main components are eleostearic acid, which contains conjugated double bonds easy to occur electrophilic addition reaction, thus forming a series of structure and different function polymer monomer, which are widely used in printing ink, paint, new type of polymer materials. So, it has important significance to carry out research on the optimization of oil product processing technology. In this paper, "Jinsi tung" and "Jingyan tung" of Hubei Wuling Moutain were as materials. The quantitative analysis of fatty acid of tung oil and sub-critical fluid extraction technology of tung oil was studied. Moreover, the eleostearic acid quantitative analysis PLS model was constructs by means of near infrared spectroscopy technology. The main results are as follows:Seed index of Jinsi and Jingyang tung tree in the dry hundred-grain weight, kernel rate and oil rate were 311.9 g,57.97%,59.94%, and 278.4 g,56.66%,56.29%, respectively. The main quality index of Jinsi and Jingyang tung oil of refraction index, iodine value, acid value, saponification value, were 1.5192(20 ℃),172.2 g/100g,2.1 mg/g, 192.2 mg/g; 1.5222(20℃),167.8 g/100g,2.5 mg/g,189.4 mg/g, respectively. From the seed quality, Jinsi tung tree kernel rate, oil rate was higher, and from the physical and chemical indicators, Jinsi tung oil quality was better.The quantitative analysis of fatty acid C16:0, C18:0, C18:1-9c, C18:2-9cl2c, C18:3-9c12c15c, C18:3-9zllel3e was developed by gas chromatography using methyl pentadecanoate as the internal standard. The results show that the correlation coefficients (R2) of all the linear regression equations of fatty acid methyl esters (FAMEs) of above fatty acid standards were higher than 0.9795; the recoveries were from 98.9% to 104.5%, the RSDs were from 4.6% to 7.3%; the fatty acid contents of Jingyang and Jinsi tung oils were 0.021 g/g,0.022 g/g,0.054 g/g,0.070 g/g,0.002 g/g,0.585 g/g and 0.018 g/g,0.019 g/g,0.071 g/g,0.069 g/g,0.003 g/g,0.729 g/g of C16:0, C18, C18:1-9c, C18:2-9c12c, C18:3-9c12c15c, C18:3-9z11e13e, respectively. The content of C18:3-9z11e13e of Jinsi tung oil was higher than that of Jingyang tung oil, which means that Jinsi tung oil has a better quality.For the purpose of improve the quality and efficiency of extraction of tung oil, tung tree seeds were extracted by the static subcritical fluid extraction technology using 1,1,1,2-tetrafluoroethane as extraction solvent. The extraction optimum extraction conditions were optimized by orthogonal experiment:raw material size,20 mesh; extraction agent,2 kg; extracting time,40 min; extracting times,3; and extracting temperature,70 ℃. The extraction efficiencies of tung oil was up to 98.12%. The quality of tung oil extracted by subcritical fluid reached the best level tung oil national standards. The fatty acid contents of C16:0, C18, C18:1-9c, C18:2-9c12c, C18:3-9c12c15c, C18:3-9z11e13e, C18:3-9e11e13e in tung oils were 4.05%,3.31%,13.27%,10,11%, 0.89%,64.83%, and 3.52%. The oil extraction process from subcritical higher than pressing extraction efficiency, which can reach 98.12%. The quality can meet the national standard of tung oil.For the purpose of rapid analysis of total eleostearic acid, by near infrared spectrometer, in the 5000～10000 cm-1 spectrum range, the spectra were pretreated with 2D+S.G(5,3). The establishment of the PLS model can achieve the accurate prediction of eleostearic acid in tung oil. In the obtained PLS model for the calibration correlation, RC value, RMSEC, the validation set Rp value and RMSEP was 0.9734,0.0145,0.8226, 0.0276, respectively. The average error and relative error was 0.0229,2.96%. Forecasting results of NIR and GC measurement results are basically the same, which can meet the requirements of rapid analysis in eleostearic acid of tung oil content requirements. |
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