| As a seasoning commonly used in life,soy sauce has a long used history in China and South East Asia.As the production of soy sauce continues to increase,how to deal with the by-product of soy sauce production-soy sauce residue has become a problem in front of people.These soy sauce residue are rich in water（70%）,salt（5%）and other substances such as oils,crude protein that can be reused.At present,soy sauce redisdue is mainly used to produce low value-added products such as feed and umami.The high salinity of soy sauce residue and the lack of deep processing technology are two factors that restrict the high value utilization of soy sauce redidue.To solve these problems,this paper uses high-efficiency electrodialysis technology to remove salt from soy sauce residue and use supercritical carbon dioxide system to convert the soy sauce redidue oil into high-valued biodiesel and the reaction mechanism and reaction kinetics were also explored.This paper also studied the extraction of high nutrient isoflavones from soy sauce residue by ethanol/dipotassium phosphate aqueous two-phase system and prepared high protein feed by using soy sauce residue.Through the above process,we have explored a process route for separation and high value utilization of the component of soy sauce residue.（1）For the two major components of salt and water in soy sauce redidue.We used electrodialysis technology to desalinate soy sauce residue.Deionized water was used as the concentrated chamber liquid,and sodium sulfate solution was used as the polar liquid.After a series of experiments,we determined the optimal desalination parameters:desalination voltage 10V,desalting time 50min,circulation flow rate 60L/h,adjust pH valve of soy sauce residue to 4.0.Under this process condition,the desalting efficiency is up to 91.6%,。The loss rate of protein during desalination process is as low as 13.4%,allowing maximum retention.The desalted soy sauce residue is evaporated to dryness to obtain a low-salt dry soy sauce residue.Meanwhile,the deionized water recoverd from the concentrated chamber is evaporated to recover the salt.Compared with the traditional water-eluting salt method,the desalination rate can be increased by 50%,the protein loss rate can be reduced by 20%,and the deionized water used as the salt ion absorption phase can be recycled,and the process does not cause secondary fermentation of the soy sauce residue.The economic accounting of this process shows that the desalting cost of this process is similar to that of the electrodialysis seawater desalination process,indicating that this process is economically feasible.（2）The dehydrated and desalted soy sauce residue is rich in a large amount of effective substances such as oil.According to analysis,the oil has been highly corroded and is not suitable for reprocessing into edible oil,but is suitable for the production of biodiesel.We use a supercritical carbon dioxide system to convert it into biodiesel in one step.The optimized production parameters are:pressure 16MPa,time 3h,temperature 100°C,raw material pulverized to 60 mesh,alcohol to oil ratio of 10:1,under which the yield of biodiesel can reach 96.8%.After detailed analysis of the mechanism of the process,it is concluded that there are five biodiesel production routes in the process.In addition,the analysis also shows that the system can automatically generate acid catalysts to accelerate the reaction during the reaction.Compared with the traditional two-step biodiesel production process,the process produce biodiesel by extraction coupling with transesterification without the need for an external catalyst,which simplifies the process and reduces the overall cost.At the same time,the biodiesel yield of this process is also higher than the 93.5%of the traditional two-step method.（3）Considering the lack of kinetic data for the production of biodiesel by one-step method under supercritical system,a kinetic model for biodiesel production under supercritical carbon dioxide was established.Through the analysis of the whole process,we believe that the whole process is that the methanol which dissolved in supercritical carbon dioxide diffuses into the interior of the soy sauce residue and reacts with the oil forming fatty acid methyl ester,then the fatty acid methyl ester is extracted by carbon dioxide and entered the supercritical fluid phase.The reaction and extraction occur simultaneously and promote each other throughout the process.Based on the Arrhenius formula,the rate constants of the three-step transesterification reaction at 100°C were 4.6*10-5(s-1),9.8*10-5(s-1),2.6*10-5(s-1)and reaction activation energy 87 KJ/mol,53 KJ/mol,47 KJ/mol.The extraction kinetics equation of biodiesel was successfully derived by the control step method and Fick’s second law.The derived kinetic model can effectively predict the progress of the reaction and provide a theoretical basis for the amplification of the supercritical process.（4）The isoflavones in the soy sauce residue were extracted by the aqueous two-phase system consisting of ethanol/dipotassium phosphate.Under the conditions of ultrasonic power 300w,temperature 70 degrees,material-liquid ratio 1:15,raw material pulverization to60 mesh and ultrasond for 50 min,the extraction rate of isoflavones can reach 95.4%.Compared with other extraction processes,the conditions of two-aqueous phase extraction process is mild,the amount of organic solvent is small,and the isoflavone yield,partition coefficient and purity are higher than the traditional methods.（5）For the residue of soy sauce residue rich in protein and crude fiber,we can obtain high protein feed after simple fermentation treatment with Aspergillus Niger and Candida.The research results in this paper prove that the process route can realize the separation and high value utilization of soy sauce residue. |
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