Comparison of Different Mechanical Methods for the Modification of the Egg White Protein Ovomucin, Part A: Physical Effects

Abstract

Egg white (EW) is required to be reduced in viscosity and particle size prior to chromatographic fractionation of single EW proteins. This study reports on an assessment of various shear devices for this purpose. Evaluation criteria for the head-to-head comparison of high-pressure homogenization, colloid mill, and toothed disc dispersing machine treatment were the achieved viscosity reduction as well as the network diminution, determined by particle size measurements. It was shown that each of the devices was able to decrease the viscosity by a reduction of fibril size. However, only the high-pressure homogenizer fulfills the requirement to disintegrate the fibrils sufficiently, so that they can be filtered through membranes with a pore size of 0.45 μm, which is indispensable for chromatographic fractionations. Generally, the achieved viscosities decreased with increasing energy input, independently of the specific shear forces resulting from the applied device. Otherwise, there was no direct correlation between the energy density and the extent of fibril destruction, indicating that the kind of energy depending on the respective device with its specific destruction mechanism was not decisive. To sum up, this study provides profound knowledge concerning the effects on the EW structure that result from different mechanical forces.

Comparison of Different Mechanical Methods for the Modification of the Egg White Protein Ovomucin, Part B: Molecular Aspects

“…As already shown in the part A of the study dealing with the macroscopic effects of the treatment (Brand et al 2015), the highly viscous egg white structure can be destroyed by the described mechanical devices (Fig. 7, part A).…”

“…According to the method described by Brand et al (2015), the shear profile consisted of an increasing ramp (0.1-120 s −1 , 3 min), followed by a holding step (30 s) and a decreasing shear ramp (120-0.1 s −1 , 3 min). Afterwards, the data of the increasing ramp were modelled using Herschel-Bulkley, and the effective viscosity at a shear rate of 20 s −1 was taken.…”

“…It was analyzed using the Malvern Mastersizer 2000 with a Malvern Mastersizer Hydro 2000S measurement unit (Malvern Instruments, Herrenberg, Germany) according to the method described by Brand et al (2014) as well as by Brand et al (2015). For the measurements, a diffraction index of 1.41 for protein and 1.33 for water was used.…”

“…The energy density E v [J m −3 ] of the used devices was calculated based on the following equations (Jafari et al 2008;Schultz et al 2004;Karbstein and Schubert 1995;Brand et al 2015;Stang et al 2001):…”

“…As already described in the part of the study dealing with the macroscopic effects (Brand et al 2015), mechanical devices like the high-pressure homogenizer (HPH), the colloid mill (CM) as well as the toothed disc dispersing machine (TDDM) are able to modify the physical properties of egg white targeted. It was shown that the viscosity can be decreased and that the egg white structure becomes homogenous by the destruction of the ovomucin network.…”