Research On The Structure Of Reverse Micelle And Its Extraction Mechanism Of Peanut Protein

Peanut protein becomes an important material of plant protein in modern food industry because of high nutritional value and good processing performance.Reverse micelles extraction is a new technology of separation and purification of biological macromolecules which is suitble for the proteins other ingredients and so on.Reverse micelles extraction has the advantages of mild condition,repeated use of solvent,which can achieve the simultaneous separation of protein and oil compared with the traditional separation technology of peanut protein.So to use reverse micelle to extract peanut protein is of great significance.At first,the change rule both of empty reverse micelle size and full reverse micelle after extracting peanut protein of AOT/isooctane reverse micelle were investigated with dynamic light scattering technique.The effects of several factors such as KCl concentration,AOT concentration,pH of buffer solution in forward extraction and different ions on reverse micelle size were studied.Results showed that reverse micelle size decreased with the increase of KCl concentration.And increase the concentration of AOT in the range of 0.04-0.09 g/mL,the size of empty reverse micelles and full reverse micelles increased.The pH had no significant influence on empty reverse micelles,but could influence full reverse micelles sizes by electrostatic interaction.The ion species had significant effects on the sizes of reverse micelles,when the addition amount of buffer solution containing MgCl2 was 0.03 mL/mL,the forward extraction rate reached the peak of 98.55±0.60%.The distribution characteristics of peanut protein in reverse micelle was further studied after the investigation of reverse micelle size change.The effects of salt concentration in buffer solution,AOT concentration,pH,and different ions on forward and backward extraction rates were investigated.The results showed that the forward extraction rates decreased and the backward extraction rates increased firstly and then decreased because of size effect when increased the concentration of KCl.In a certain range,the greater the concentration of AOT,the smaller the forward extraction rate,and the backward extraction rate was on the contrary.The variety of AOT concentration had no significant effect on the distribution coefficient of the two phase.The pH affected the solubilization of peanut protein in reverse micelle through electrostatic interaction.The ion species had significant effects on the distribution characteristics of full-fat peanut protein and the effect of cation species was larger than anion species.The relationship between reverse micelles sizes and extraction rates could influenced by many factors,and their relation varied under different conditions.The model of the forward extraction process was "water-shell model".The relationship between reverse micelle size and the extraction rate of the forward extraction rate was not linear,so the influence of some other factors on the back extraction was studied further.The influence of the factors such as oscillation rate,AOT concentration,the amount of the peanut powder added into reverse micelle and other factors on the backward extraction was researched.The results show that the oscillation rate had no significant influence on the backward extraction,when the concentration of AOT increased from 0.03 to 0.06 g/mL,the total mass transfer coefficient reached a maximum of 2.12×10-5/m3·s-1,which tells that the extraction of peanut protein by reverse micelles is not controlled by mass transfer diffusion resistance,but controlled by the interface resistance.When the amount of the peanut powder added into reverse micelle was 0.015 g/mL,the total mass transfer rate reached 0.93×10-5/m3·s-1,it was further proved that the peanut protein was controlled by interfacial resistance.Finally,the effects of reverse micelle sizes and some other factors on structure and properties of protein were investigated.The effects of reverse micelle sizes,KCl concentration,AOT concentration on molecular weight of peanut protein subunit,the content of thiol group and two disulfide bond,the two stage structure,the emulsifying property and emulsion stability were studied.The results showed that KCl concentration and AOT concentration influenced the protein significantly through reverse micelle size.Large molecular proteins increased with the increase of reverse micelle size.The contents of mercapto group and disulfide bond reach to their peaks when the reverse micelle sizes increased to 8 nm and 10 nm,respectively.The size of reverse micelle also had some influence on the secondary structure of protein,the secondary structure of protein extracted by smaller size of reverse micelle was more disordered,and the larger size of reverse micelle had a protective effect on protein.With the increase of reverse micelle size,the emulsifying ability of the protein gradually increased and then tended to be stable,and the emulsion stability decreased gradually.