Study On The Preparation And Properties Of Peanut And Soybean Protein Emulsion And Gel

Peanut oil and protein can simultaneously extract by the aqueous method,and the obtained protein was not processed at high temperature,which can retain the original structure and functional properties to the greatest extent.At present,researches were not yet in-depth on the important functional properties of the peanut protein obtained by this method,which limits its application in the food industry.In this paper,the peanut protein isolate(PPI)by aqueous method was taken as the object to study the effects of different emulsification methods on emulsion stability,and compare the emulsifying properties and emulsion gel properties of PPI and soy protein isolate(SPI)and their components based on high-intensity ultrasound(HIU)prepared emulsion,which provide a theoretical basis for the application of peanut and soybean protein.By single factor experiment,the optimal high-intensity ultrasound(HIU)emulsification conditions consisted of a concentration of 4%(w/v)proteins,a volume percentage of 30%(v/v)oil,and an ultrasonic treatment at 300 W for 20 min.Compared with the two emulsions prepared by high-pressure homogenization(HPH)at 300 and 500 bar,respectively,the HIU-prepared fresh emulsion showed a larger particle size,similar zeta potential but higher interfacial protein concentration(?)and apparent viscosity.Additionally,the HIU-prepared emulsion had lower flocculation and coalescence indices and was more resistant to gravitation separation during storage.Isolation and characterization of the non-adsorbed proteins from the HIU and HPH(500 bar)prepared emulsions.The non-adsorbed proteins from the HIU-prepared emulsion had unique structural characteristics,such as higher molecular weight,more unordered secondary structures,and stronger surface hydrophobicity and the obvious red shift of intrinsic fluorescence emission spectroscopy.The results showed that HIU can not only efficiently broke the oil droplets,but also modify the structure of protein,thus improving the stability of emulsion.Comparing the emulsifying of HIU-prepared emulsion which stabilized by PPI,SPI and their components(arachin,conarachin,glycinin and conglycinin),respectively.The results found that SPI and its component emulsions showed smaller particle size,higher?value and viscosity.Compared with component protein emulsions,PPI and SPI had the lowest emulsion coalescence index and best centrifugal stability.After adding the conglycinin can significantly improve the viscosity,?and centrifugal stability of conarachin and arachin emulsions.Correlation analysis showed that EAI was significantly positively correlated with viscosity,and negatively correlated with particle size and potential(absolute value).The centrifugal stability of emulsion had a significant positive correlation with surface hydrophobicity and viscosity,and negative correlation with particle size.The results of stability of the emulsion under different environmental conditions,it observed that HIU-prepared emulsions were stable after storage for 4 weeks at 4°C.The freeze-thaw stability of the conglycinin emulsion was the best,followed by the PPI emulsion,and the addition of conglycinin significantly improved the freezing of conarachin and arachin emulsions.Conglycinin emulsion showed the best salt stability,followed by the PPI emulsion,and the salt stability of recombinant protein emulsions was better than conarachin and arachin emulsions.The PPI emulsion prepared by HIU as the research object,the optimal induced emulsion gels were the concentration of 0.3%(w/v)gluconolactone(GDL),0.15 g/d L Ca Cl₂and 25 U/m L transglutaminase(TGase),respectively.The results of emulsion gel properties found that GDL induced gel strength of conarachin was the highest,followed by PPI,but gel water holding capacity of PPI and its components were weaker than that of SPI and its components.The Ca Cl₂ induced gel strength of conglycinin was the highest,followed by SPI,and the lowest gel strength was conarachin,while SPI and its components emulsion gels had better water holding capacity than others.The TGase induced gel strength of conarachin was the highest,while the lowest gel strength was arachin,and SPI emulsion gel possessed the best water holding capacity.Analysis of the dynamic rheological properties of GDL-induced emulsion gels showed that the lowest gel formation temperature was glycinin emulsion(48.3°C)and the highest were SPI and s conglycinin emulsions(80.0°C).During the test time,SPI and conglycinin emulsion gels had the largest elastic modulus(G?),followed by PPI and conarachin emulsion gels,while the G?of glycinin and arachin emulsion gels were the smallest.The micro structure of protein emulsion gels was observed by laser confocal scanning microscope(CLSM).It was showed that the PPI emulsion gel possessed a good network structure with small amount of pores and uniform oil droplets;the conarachin emulsion gel network was dense and uniform,while the oil droplets were arranged neatly;the glycinin emulsion gel had dense protein network,but the oil droplets were in different shapes;the network structure of others were poor with large pores,which were consistent with gel strength.