The Composite Gel Properties Of Egg White And Soybean Protein Isolate

Egg white and soybean protein isolate, which have been widely used in many food becauseof their gel properties, are the representative animal protein and vegetable protein. This paperinvestigated the composite gel properties of egg white and soybean protein isolate to obtain a newtype of composite gel with better gel properties and lower cost. Meanwhile, the research providedtheoretical basis for the further investigation of different kinds of animal proteins and vegetableproteins. In addition, this article also applied the theory to the soybean milk and egg white mixedsystem to provide theoretical guidance for practical production.Firstly, at the protein concentration of10%, the thermal gel properties of soybean proteinisolate and egg white blended in different protein ratios were investigated. The springiness andwater holding capacity (WHC) increased at first then decreased with the addition of egg whiteand all showed the highest values when soybean protein isolate and egg white blended at the ratioof1:1. The secondary structure of gels showed that the level of ɑ-helix were positively correlatedwith the springiness, water holding capacity and the level of β-sheet were positively correlatedwith the hardness of gels when the content of egg white increased.Secondly, the composite acid gel properties of soybean protein isolate and egg white, usingdifferent blend ratios and protein concentrations induced by glucono-δ-lactone (GDL) werestudied. At the protein concentration of3%, the added egg white decreased the gel properties. Atthe protein concentrations of6%,8%,10%, the hardness, springiness and WHC of acid gelsshowed similar trends to the thermal gels with the increase of egg white. At the proteinconcentration of6%, the degree of synergistic enhancement showed the highest value. Besides,the rheological properties and microstructure of acid gels blended in different ratios at the proteinconcentration of6%were also investigated. When the content of egg white increased, storagemodulus of gels increased which showed positive correlation to the hardness. The gelation timeand temperature were decreased with the addition of egg white. The microstructure showed thatthe gel formed a more uniform network at the ratio of1:1. Moreover, the secondary structure ofproteins during gelation were investigated. With the temperature increased, the level of ɑ-helixdeclined gradually and β-Sheet increased. When cooled down to40oC, the level of ɑ-helix andβ-Sheet were both increased.Thirdly, based on the above study, the research to improve the properties of composite acidgel were investigated. When the soybean protein isolate were preheated at90oC for10min with0.05g/g protein of GDL and gelled under85oC for30min, a composite gel with better gelproperties could be produced.Finally, the composite gel properties of soybean protein isolate and egg white were appliedinto the practical mixtures of soybean milk and egg white. At the protein concentration of6%,when adding50%of egg white, the quality of samples were relative better. Amino acid analysisshowed that the samples contained more methionine than that of the soybean product alone.