| Soybean contains not only a lot of high-quality protein and unsaturated fatty acids, but also a variety of physiological active substances, such as soybean oligosaccharides, soybean saponin and soybean isoflavone. Soy saponins can fight inflammation, ulcer and some cancer, reduce blood cholesterol content, inhibit the formation of blood clots, reduce the incidence of cardiovascular disease, prevent lipid peroxidation from generating and delay the ageing of the body. For extraction of soybean saponin with biological activity and medicinal value, in this paper, different extraction methods of soybean saponin were studied using the waste residue of the soybeans as raw materials And the influence of soxhlet extraction method, organic solvent refluxing extraction, microwave extraction method, ultrasonic extraction method and supercritical fluid extraction on yield of soybean saponin were studied and the extraction methods were compared. In addition, the dynamics and thermodynamics mechanism in the extraction process of soybean saponin with organic solvent method were also studied.1. The experiments of extraction for soybean saponin with different methods of soxhlet extraction, organic solvent reflux extraction, microwave extraction, ultrasonic extraction and supercritical fluid extraction respectively were done, and these methods were compared using the extraction time, extraction temperature, solvent type and concentration, grain size, extraction pressure and power as indexes. The results show that the yield of 0.97% with soybean saponin with supercritical extraction method is the highest, the technological process is short and has no pollution, and the product has high quality, but the experimental equipment is complex and expensive. The yield of 0.362% with soxhlet extraction is very low, its temperature is 95 ℃ and its extracting time is up to 5 h. The yield of 0.703% with organic solvent refluxing method is higher than the soxhlet extraction, but with many experimental procedures and large amounts of organic solvent. The extracting time of microwave method is short, with the soybean saponin yields of 0.832%, its experiment steps are simple and the extraction temperature is low. And the yield of 0.900% with ultrasonic extraction is high, with low extraction temperature and short extraction time, but ultrasonic pollution in it is difficult to remove. Taken soybean saponin production rate, extraction time, extraction temperature, the amount of solvent consumption, and complexity of extraction equipment into account, the methods of microwave assisted extraction have higher yields, with low extraction temperature, short time and little cost of experimental equipment, and are more likely to be used for industrial production than other methods.2. The dynamics theory of extraction process of soybean saponin from soybean dregs is studied in the paper, and the dissolution process of saponin molecule is observed. On the base of Fick’s first diffusion law, the dynamics model about extraction process is established. The results show that, at temperature of 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, the linear relation of logarithm of concentration and logarithm of time is fine within a certain period of time, the experimental data are correlated with the dynamics model. The data correlated in the model show good agreement with the experimental data.3. Thermodynamic mechanism of extracting soybean saponin with organic solvent refluxing extract method was analyzed, and energy change during the saponin dissolution process was calculated. Variation of thermodynamic function value in the process of extraction, such as enthalpy, entropy and gibbs free energy, were calculated. The results showed that during the extraction process of the soybean saponin, 0/332.260S>=D mol J,the entropy in the process of extracting soybean saponin is increasing; 0/68740H>=D mol J, the process is endothermic; 332.266874TG0-=D, Gibbs free energy decreases with the increase of temperature.. |
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