Garlic Oil Extracted By Countercurrent Supercritical CO₂ & Garlic Polysaccharide Extraction From The Raffinate

After garlic was pressed or fragmented, allinase in garlic will convert alliin to allicin and other volatile sulfur compounds, which are the main compositions of garlic oil. The extraction yield and quality of the garlic oil by using supercritical carbon dioxide (SC-CO2) is high, but the water content of the garlic is high and the bulk density of fragments is big,that reduce pressure drop of CO2 in extraction, CO2 penetrate nonuniformity, and made it difficult to scale up for industrialization. After garlic was squeezed, the fluidity of garlic juice and mass transfer between the juice and SC-CO2 are good, so continuous countercurrent supercritical fluid extraction (CC-SFE) could be carried out in high performance extraction column, which made industrialization be feasible. A ton garlic oil could be extracted from 200~300 tons garlic, the remainder of extraction contain more than 30% of soluble solids which are primarily polysaccharide and a little quantity of protein, whose exploitation value are much higher. The paper studied the technology of garlic oil extracted from garlic juice by using CC-SFE and garlic polysaccharide extracted from the raffinate. 1.According to the theory of supercritical fluid phase equilibrium, two sets of phase equilibrium apparatus were designed respectively for single-pass method and recirculation method. By means of these apparatus, phase equilibrium of garlic oil among garlic juice in SC-CO2 was studied. On the base of rectify system of the original supercritical fluid extraction device, equipment modification for CC-SFE were accomplished and garlic oil extraction by using CC-SFE was studied. 2.The technical parameters were optimized to improve garlic juice extraction by using pectinase. According to the study of the key factors, such as pH, hydrolysis temperature and time, the level of pectinase addition which affected the rate of garlic juice and the content of allicin, the optimal technical parameters were determined, in the suitable range of pH, the addition of pectinase was 0.4%, the temperature and time of water bath were 40 ℃and 120min respectively, among these factors, the level of pectinase addition affected allicin notably. Under those conditions, the garlic juice yield was 74.8%, the concentration of allicin was 3.46mg/g, the total content of allicin was high, and the operation of squeeze and filtration became easier. Garlic fragment was incubated in 40 ℃for different time, and then extracted with diethyl ether; the extracts were analysis by using gas chromatography-mass spectrometry (GS-MS). The result showed that the effecting on composition of allicin was limited under 40 ℃water bath for 120min. 3.The solubility of garlic oil in different states'SC-CO2 and the distribution coefficient of balance system were studied by employing the phase equilibrium apparatus. The result indicated that the solubility of garlic oil in SC-CO2 at 40℃was remarkably higher than the solubility at 35 ℃; when the SC-CO2 pressure were 10MPa, 15Mpa and 20MPa, the garlic oil solubility had not significant difference, but those solubility were remarkably higher than under 8MPa pressure; The experiment showed that the optimal supercritical CO2 extraction conditions were 40 ℃and 15Mpa, the solubility of garlic oil in SC-CO2 got up to 0.7076g/kgCO2 under the conditions. The ratio of solvent to fluid in extraction(S/F=13.3)was high for the lower distribution coefficient of garlic oil in SC-CO2. 4.The optimum extraction and separation conditions were investigated in the batch operation of garlic oil extraction by supercritical CO2 from garlic juice. The result showed that the extraction efficiency could be improved greatly adding packing in the extractor. The optimum extraction condition was 15MPa, 40 ℃and CO2 flow rate 3500g/h; The optimum separation condition was 8MPa and 35 ℃in the separationⅠ, 5MPa and 25 ℃in the separation Ⅱ. Analysis by GC-MS, the composition of garlic oil extracted from the garlic juice was same as that from garlic fragments by SC-CO2 extraction, and the concentration of allicin was more than 40%. 5.The key factors, which affected garlic oil extraction by countercurrent supercritical carbon dioxide, were investigated by factor analysis. The level of garlic juice introduction into the extraction column (LevelIn) had the most important effect on the rate of garlic oil extraction, CO2 flow rate (CO2Flow) and sample flow rate (SampFlow) were minor; The extraction yield of garlic oil was positive correlation with the LevelIn, the higher the level, the longer the time of garlic juice contacting with SC-CO2, the more the extraction yield; The extraction yield was negative correlation with the SampFlow, the less the flow rate, the higher the rate of solvent and feed(S/F), the more the extraction yield; In a certain range, to increase the CO2Flow could enhance the S/F that improves the extraction yield, but when the CO2Flow continued to increase and near to the flooding rate, the effect of extraction became worse and the extraction yield dropped. The regressive model of garlic oil of countercurrent SC-CO2 extraction was obtained by quadratic polynomial regression fitted to the experimental data. The regressive equation was good in fitting to the experimental data after evaluation. The optimum conditions of CC-SFE were the CO2Flow of 3124g/h, the SampFlow of 200g/h, the LevelIn of the top. On these operations, the extraction yield would get up to 0.432%. 6.The major polysaccharide, the main compositions of garlic juice, were repeatedly treated of degreasing, removing protein and pectin, grading alcohol depositing, purified with SephadexG-25,SephadexG-50, at last the pure garlic polysaccharide was obtained. After acid hydrolysis digest of the garlic polysaccharide was analyzed by thin-layer chromatography (TLC) and high performance liquid chromatography (HPLC), the compositions of garlic polysaccharide were ascertained to be fructose and glucose, and the ratio fructose to glucosewas 7.95:1; The garlic polysaccharide glycosidic bond was ?-style configuration after being analyzed by infrared spectrum (IR); Measured the garlic polysaccharide by high performance gel permeation chromatography (HPGPC) and referred to glucan of standard molecular weight, the molecular weight of the garlic polysaccharide was calculated to be 5038Da; The thermal stability of garlic polysaccharide liquor was good, but the acid stability was worse. 7.The extraction technique of crude garlic polysaccharide from the reffinate of the CC-SFE had been studied. The result indicated: in removing protein from the raffinate, the effect of heating method was better than isoelectric point method and adding tannin method, the protein removing rate was 96% by heating 30min at 90℃. The pectin removing rate reached over 97% by adding 0.01mol/LCa2+; The light transmittance of the polysaccharide liquid reached 99% by adding 6% active carbon and heating 30min at 90℃; compared with ethanol depositing, the garlic polysaccharide mixture which was produced from directly concentrated and dried preserved had not only macromolecule garlic polysaccharide but also had small molecular oligosaccharide. The extraction technique of garlic polysaccharide from the raffinate that had extracted garlic oil was simple, and the garlic polysaccharide had little impurity such as protein, pectin and etc, white color, and would be a kind of ideal healthy foodstuff.