Study On Preparations And Applications Of Liquid Egg White With High Foaming Property

Foaming property of egg white protein is widely used in baking food. This study mainly focused on the effects on the foaming property of egg white protein brought by modification methods such thermal treatment, ultrasonic treatment and food additives, then processing technology with both excellent foaming capacity and foaming ability was found on the base, the results of the study are as follows:Foaming property of egg white with different dilutions was studied, treated under the conditions that holding 3minutes when temperature rose to 55℃. As the results showed, foaming capacity presented an increasing trend with the rising extent of dilution while the foaming stability presented opposite, howerer, the foaming capacity improved significantly as well as maintaining good foaming stability under the dilution of 20%. Thermal treanment led changes of protein aggregation morphology, while diluting egg white effected the foaming property in the ways that changing the morphology and extent of protein aggregates and also the amount of free –SH and hydrophobicity groups and so on.The effect of ultrasonic treatment on foaming property of egg white was researched. It was found that foaming capacity was improved significantly by ultrasonic treatment while foaming stability was destroyed. Foaming capacity was higher significantly than that of untreated egg white,presenting a tendency of rising perpendicularly along with a slight decline with the rising ultrasonic power and the extending ultrasonic time, while foaming stability dropped first and then rose up again, never reached that of untreated egg white. In all, a foaming capacity of 260.00% was achieved under the conditions of ultrasonic treatment with 360 w in 10 minutes. Analyzing in various aspects, ultrasonic treatment increased protein solubility, the sulfhydryl content, surface hydrophobicity and so on, meanwhile, it reduced the surface tension and viscosity of the system, Scanning electron microscopy showed that ultrasonic treatment changed the the morphology of protein and the form of aggregates, change in amount and structure of some proteins in egg white were observed by SDS-PAGE.Ovalbumin, which was highest in content and influence foaming property greatest in egg white, was extracted to analyze the microstructure. The UV absorption spectrum and intrinsic fluorescence spectroscopy showed ultrasonic treatment further exposed aromatic amino acid such as tryptophan and tyrosine in ovalbumin, making structure more stretch and hydrophobicity increasing.X-ray diffraction curves showed that ultrasonic treatment influenced the crystal structure of ovalbumin slightly. The analysis results of CD spectrum indicated that ultrasonic treatment reduced the content of α-helix while increased the amount of β-turn and random coil, improving the flexible of ovalbumin.In order to improve foaming stability of ultrasonication treated egg white, xanthan gum was choosed. Xanthan gum solutions with different concentrations(0.3%、0.6%、0.9%、1.2%、1.5%)were treated under different ultrasonic power(90W、210W、330 W、450W、570W) and various ultrasonic time(6min、12min、18min、24 min、30min) in a discontinuous mode(30s on,60 s off), then mixed with ultrasonication treated egg white at a volume ratio of 1:9. With the increase of ultrasonic power and ultrasonic time, foaming capacity increased monotonically while foaming stability dropped monotonically, and the higher was the concentration, the better foaming stability was,even though foaming capacity declined. The result of orthogonal test showed that a better foaming capacity of 206.33% and an excenllent foaming stability of 95.86% were both obtained under the condition that: xanthan gum concentration at 1.1%, ultrasonic power at 330 W, ultrasonic time at 15 minutes. The viscosity and the volume rates of large aggregates were enhanced by xanthan gum. Rheological investments showed that the storge modulus G’ of both untreated egg white and egg white treated under optimal process were higher than the loss modulus G″all the time, but a slight increase in the storge modulus G’ was found for egg white treated under optimal process, which presented a more elastic fluid property. The rheological curves showed that pseudoplastic of egg white treated under optimal process was stronger.The sensory evalution and texture profiles of angel cakes made by egg white treated under optimal process were similar with those made by untreated egg white when applied in angel cakes for a contrast experiment with untreated egg white, while the amount of egg white usage and the whipping time of foaming decreased, the contrary that the springiness and water-holding capacity increased when angel cakes were made by egg white treated under optimal process, which would benefit saving production time, enhancing production efficiency and improving production quality.