Study On The Mass Transfer Kinetics In Reverse Micelle System Extraction Of Soy Protein

Although soy protein is a plant protein,its nutritional value is rather high and its amino acid composition is close to the milk protein's which makes it more easy to be absorbed.Soy protein also has good functional properties,therefore,soy protein commonly used to ameliorate the quality and nutritional value of the products,such as pasta,beverages,meat.Alkali extraction and acid precipitation,as a traditional industrial process for the production of soybean protein,occupies the low extraction rate,too much pollution and complex process.Reverse micelles not only solves the above-described problems,but also can protect the protein and it's biological activity from the harm of organic solvents owing to the "water pool"in the reverse micelles.Now reverse micelles attracts more and more scholars'attention,as a new technology to extract soybean protein isolate.At first,This paper studied the distribution change of soybean protein in the reverse micelle phase,the aqueous phase and the organic phase during the process of sodium bis(2-ethylhexyl)sulfosuccinate(AOT)reverse micelles extracting soybean protein.This studied the effect of the various factors on the rate of forward extraction and back extraction,the total extraction rate and partition coefficient,through changing the conditions of forward extraction and back extraction.The results showed that The forward extraction rate of soybean is maximum value when it was at AOT concentration 0.08 g/mL,pH 6.5,KCI concentration 0.05 mol/L,temperature 40? and water addition 0.08 mL/mL.the former four factors influenced the transfer of soybean protein during the back extraction as to as the forward extraction,while temperature of forward extraction had no effect on the protein transferring to the water phase.The back extraction rate was the highest when the conditions of back extraction were that pH 8.0,KCI concentration 1.0 mol/L,temperature 30? and time 30 min.Secondly,it also studied the kinetics of forward eatraction and backward extraction in AOT reverse micelles system and CTAB reverse micelles system.The process of forward extraction is similar to the reaction during solid-liquid process,so it chanced the unreacted core model.By controlling the concentration of AOT and W0 value to watch the change of soybean protein rate of forward extraction and back extraction,it was determined whether the extraction process meted to the model.It turned out that in the two reverse micelles,the reaction takes about 30 min to reach equilibrium,and improving appropriately the temperature and W0 was beneficial to the increasing forward extraction rate.It was confirmed that the control step is the diffusion in the product layer.The equation of mass transfer process of peanut protein extracted by AOT and CTAB reverse micelles was established,and the reaction activation energy is 12.89 kJ/mol in AOT reverse micelles,and 19.98 kJ/mol in the CTAB reverse micelles.During the back extraction process in the two reverse micelles,the back extraction rate is increasing with the W0 improvement.At the same W0,the higher surfactant concentration,the lower back extraction tare.By comparing the mass transfer kinetics in AOT and CTAB reverse micelles,we found they had similar kinetics,and the unreacted core model and double-film theory conform to the forward extraction and back extraction respectively.At last part,we studied the functional properties change of soybean protein which extracted by the reverse micelles under various condition.We got the result that improving AOT concentration.KCl in forward extraction and back extraction and time in the back extraction,made polar amino acid residues in the interior of soybean protein exposed and the amount of surface charge improved.The change of surface charge influenced protein emulsification and emulsion stability.With the increase of the amount of soy protein surface charge,hydrophobicity/hydrophilicity ratio was decreased,and it also influenced the amount of protein in the oil-water interfacial adsorption,therefore reduced soybean protein emulsion.Increasing in protein surface charge lead to that the electrostatic repulsion between protein molecules was increased,and stability of the emulsion was decrease,thereby emulsion stability of soy protein was reduced.