| Double low rapeseed,which is rich in triglyceride oil and minor lipids components such as phospholipids,VE,sterol and Canolol,is a high quality oil and vegetable protein resource.Rapeseed cake,produced by low press from double low rapeseed,contains some residual lipids.For usual,n-hexane is used to fully extract residual lipids of rapeseed cake.The high temperature desolventizing process in n-hexane extraction will lead to the lipids and meal quality deterioration.Subcritical Fluid Extraction?SFE?has numerous advantages such as milder dissolution temperature,higher extraction efficiency and lower production costs.As a new extraction and separation technology,SFE prove to be a good alternative to n-hexane extraction.However,it is found that the systematic and fundamental research were performed rarely in the double low rapeseed and its pressed cake.Therefore,a systematical research of SFE is carried out using the double low rapeseed cold pressed cake as trial material.And then the transfer rule and solubility properties of rapeseed oil and minor components is found out in a SFE process.Extraction mechanism and kinetics of SFE is studied,meanwhile the basic subcritical lipid extraction data is obtained.The results of paper are as follows:1.The processing of Subcritical Butane Extraction?SCBE?in rapeseed oil is studied.A Box-Behnken response surface method is used to optimize SCBE conditions,the experimental result indicated that liquid to material ratio and extraction time had significant effect on the extraction rate of rapeseed oil,and there was significant interaction;the best extraction conditions is found that liquid to material ratio is 8.3 mL/g,90 min for the extraction time,35?for extraction temperature;under best conditions,the extraction rate of rapeseed oil is higher as 95.10%.Rapeseed oil obtained by three kinds of method are be compared for their quality,which results show that SCBE's oil color is lighter than n-Hexane Extraction?HXE?oil's,and phosphorus content of SCBE's oil is 113.20 mg/kg,which is half of HE's oil,meanwhile acid value and peroxide value of SCBE's oil are significantly better than HXE's.It is found that phosphorus content of rapeseed oil produced by Supercritical CO2 extraction?SCO2E?is lowest than the other two process,the rest of quality indexes of SCO2E's oil has no significant difference with SCBE's.2.The apparent structure of crushed rapeseed powder,measured the average particle size of 489?m, is analyzed by Scanning Electron Microscope?SEM?,and the SEM's pictures showed that rapeseed cake particles have a uneven surface,which oil occurred on,there are many holes with different sizes and some pores extending into pellets.A dissolution law is studied for the SCBE process,the results show that changes of extraction temperature at 2050?and extraction time is less than 12 min,a linear increasing trend of oil extraction rate is found in the SCBE process,meanwhile there is negative correlation between the extraction rate of increase velocity and temperature and after 30min extraction,the oil extraction rate of growth is not obvious.When extraction temperature is 2050?,phospholipid content of rapeseed oil increases rapidly with the increase of extraction time,and a positively correlated is found between phospholipid content growth velocity and extraction temperature after extracting15min.The extraction temperature had a significant effect on the SCBE of phospholipids from rapeseed oil.When the extraction temperature was low?20??,the dissolution rate of VE in rapeseed cake was slower,and the dissolution of sterols was more sensitive to temperature change.When the extraction temperature is higher?4050??,the extraction time and temperature can significantly affect the dissolution of Canolol.3.The internal microstructure of rapeseed and cake was observed by Transmission Electron Microscope?TEM?.The TEM's picture show that the cell structure of rapeseed press cake was completely destroyed and most of the oil body was extruded and fused.At the same time,some small oil body with whole structure retained in the structure of defective fusion protein body.After the SCBE,the area of oil body fused in the cake is further reduced and structure of small oil body is destoryed by solvent,and then most of the lipids were extracted,leaving only the skeleton of the protein.The results of a kinetics research on SCBE show that the Patricelli model can be used to describe the kinetic properties of rapeseed oil and minor components,such as phospholipids,VE sterols and Canolol in the SCBE process from cold press rapeseed cake.The extraction mechanism is mainly washing oil and minor components occured the surface of the cake,which is spontaneous in the whole process.At lower temperatures,VE was most likely to be extraction accompanied by triglyceride,followed by sterols,phospholipids and Canolol extraction was the slowest.Moreover,at higher temperature,the mass transfer coefficient of phospholipid increased dramatically,which lead to extract largely,and the mass transfer coefficient of Canolol increased greatly,which was close to that of VE and sterol.The results of thermodynamic study show that the activation energy of phospholipid extraction is the highest,and the lower temperature can be used to extract the phospholipids littlely.The activation energy of VE is the lowest,and it is easier to be extracted at lower temperature.4.The solubility properties of rapeseed lipids in subcritical solvent is studied and the values of Hansen Solubility Parameters?HSP?are calculated by using Group Contribution Method?GCM?.The results show that Sterol and?-Carotene of solubility in n-butane are slightly better than VE's,which have a close solubility to rapeseed oil.The solubility of phospholipids was very different,and the average value of Ra,the distance of a solvent from the solute,is 11.81?J/cm3?1/2,which is 1.37 times to the average VE's.The solubility of Canolol in n-butane is relatively poor,and Ra is up to 15.13?J/cm3?1/2.The extraction process,which is limited by solubility,the extraction rate of sterols,?-Carotene and VE was faster,and phospholipids and Canolol were slower.There is a linear relationship?R2=0.752?between the Ra value of rapeseed lipids with n-butane and the mass transfer coefficient at 20?.5.The factors affecting the solubility of subcritical extraction system were investigated,the results indicate that the HSP of n-butane and R134a are greatly influenced by temperature.When the temperature changes from 0?to 50?,the?d of n-butane decreased from 14.96?J/cm3?1/2 to 13.17?J/cm3?1/2,and the?d,?p and?h of R134a is decreased at 18.l2%,7.7%and13.6%,respectively.The HSP of rapeseed oil,VE,sterol and Canolol are not significantly decreased in the range of 0?to 50?.The mixture,n-butane mixed with R134a,has a large increase in regulation freedom degree of solubility.With the decrease of the ratio of n-butane and the increase of the ratio of R134a in the mixed solvent,the solubility of rapeseed oil,VE,sterols,phospholipids and?-Carotene in the mixed solvent increased firstly,and then show a decreasing trend.With the increase of R134a ratio,the solubility of Canolol firstly increased slowly and reached the maximum at 1:1?n-butane to R134a?,then decreased rapidly.Therefore,the selectivity,Canolol is extracted by subcritical solvent,can be significantly improved by adjusting the ratio of n-butane to R134a. |
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