| Flax is one kind of linaceous annual or perennial herb, which belongs to dicotyledon outline and rose sub-outline. It is one of the world’s top ten oil crops with widespread distribution and glorious planting history in China. Flaxseed is the seeds of flax, which mainly contain fat, protein, sugars, etc. Because the flaxseed oil is rich in linolenic acid, linoleic acid and oleic acid, it has nutritive value and medicinal efficacy. The research object of this thesis is flaxseed, and the nutritive flaxseed oil were extracted, analysed and identified, the extraction process is optimized as well. The kinetics of solvent extraction process was also studied, and the data of extraction kinetics were measured, which laid the foundation for the further application of the flaxseed oil. The main research contents and conclusions are listed as follows:(1) The chemical compositions of flaxseed oil were analyzed by GC-MS method. There were ten species of fatty acids separated and identified in flaxseed oil, which were consisted of six saturated fatty acids(17.62%) and four unsaturated fatty acids(82.38%). The saturated fatty acids are mainly composed of tetradecanoic acid (0.11%), hexadecanoic acid(12.17%)and octadecanoic acid(5.16%). And the unsaturated fatty acids are mainly composed of linolenic acid(74.01%), oleic acid(0.21%) and linoleic acid(8.01%). (2) Based on the single-factor experiments, response surface methodology was used to optimize the conditions for n-hexane extraction of oil from flaxseed. The result indicated that the optimum extraction conditions were temperature of56°C, extraction duration of2.2h, liquid-to-solid ratio of8:1(mL·g-1) and stirring rate of310r·min-1. Under these optimize conditions, the predicted and observed values of maximal extraction yield of flaxseed oil were98.28%and98.12%respectively, suggesting that the optimal extraction conditions are reliable.(3) The effects of stirring speed, liquid-solid ratio, extraction temperature and particle size on the process of conventional solvent extraction of flaxseed oil were examined. The extraction rate of flaxseed oil were observed at different extraction conditions, the result showed that the extraction rate could be promoted with reduced particle size, higher extraction temperature and improved liquid-solid ratio appropriately. Meanwhile, the influences of various factors were analyzed and the extraction mechanism was preliminary studied. The kinetic model of conventional solvent extraction was established, and it was validated by experimental data. The control step of the conventional solvent method was internal diffusion control, and the macro kinetic equation was also established, the result showed that the calculated value and the experimental value had a good match. The macro kinetic equation was as follow:1-3(1-x)2/3+2(1-x)=1.66×10-4·exp(-13.72/RT)·M0.58·1/r02·t(4) The microwave-assisted method was used to instead of the traditional heat source for the extraction of flaxseed oil. The effects of several factors such as extraction temperature, particle size, microwave power and liquid-solid ratio on the extraction rate of flaxseed oil were investigated. The extraction rate was higher and extraction time was shorter with microwave-assisted method. At the same time, the mechanism of extraction with microwave-assisted extraction (MAE) was also discussed. It is considered that the control step of the extraction process with MAE was internal diffusion control. At last, the macro kinetic equation of MAE were established, the scatter diagram that established by calculated value and experimental value indicated that it can preferably reflect the extraction process of flaxseed oil. The macro kinetic equation was as follow:1-3(1-x)2/3+2(1-x)=6.84×10-5·exp(-9.75/RT)·P0.18·M0.74·1/r02·t... |
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