# Effects of Supplementation of Different Proteins on the Rheological Properties of Liquid Whole Eggs
## 4 Discussion  
The viscosity of liquids, in general, is influenced by several factors, including temperature, molecular structure, and the interactions between molecules. Usually, as temperature increases, the viscosity of a liquid decreases, due to the fact that molecules line up easier, allowing it to flow easier [26]. Molecular structure also has a huge effect on viscosity; the more complex the structure is, the more it resists flowing. This resistance can happen due to the strong intermolecular bond between the liquid molecules, which increases the overall viscosity [10]. In the case of liquid whole egg, viscosity is primarily affected by the protein content and how these proteins interact with each other. Proteins in the egg, such as ovalbumin and ovotransferrin, can form networks that trap water and increase resistance to flow, especially when subjected to heat [26]. This explanation is clearly seen in the results of \(\tau_{0}\); it increased significantly with the increase in added protein percentages, and drastically increased when heat was applied after adding the protein. Adding different percentages of whey or egg white powdered proteins influences liquid whole egg viscosity. With the increase in protein content, the viscosity increases; this is due to the several types of protein interactions that occur in the solution [27]. Why protein solution shows near-Newtonian behavior at a low concentration when no heat treatment is applied, but tends to show shear thinning behavior at a high concentration or when heat treatment near the whey protein denaturation temperature is applied, which ranges from 65 to above 70 \({}^{\circ}\)C. In this experiment, whey protein was dissolved in liquid whole eggs, then heated to 60 \({}^{\circ}\)C; this temperature is a relatively mild heat treatment for whey protein [28]. At this temperature setting, ovalbumin in egg whites and \(\beta\)-lactoglobulin in whey may start to partially unfold, leading to the exposure of hydrophobic regions and reactive sites on the proteins. This could facilitate hydrophobic interactions and some degree of aggregation between whey and egg proteins, but the extent of bonding is limited at this temperature [29]. Another interaction that may affect the mixture properties is disulfide bonds. Both egg and whey proteins contain the sulfhydryl group. Although 60 \({}^{\circ}\)C is not the optimal temperature for disulfer cross-links to occur, a weak interaction can occur [29]. \begin{table}
\begin{tabular}{c c c c} \hline
**Sample** & \(\tau_{0}\) & K & n \\ \hline Control & 0.031 \(\pm\) 0.035 & 0.002 \(\pm\) 0.001 & 0.986 \(\pm\) 0.022 \\
3\% added whey protein & 0.043 \(\pm\) 0.040 & 0.007 \(\pm\) 0.001 & 1.006 \(\pm\) 0.020 \\
5\% added whey protein & 0.053 \(\pm\) 0.003 & 0.010 \(\pm\) 0.002 & 1.030 \(\pm\) 0.010 \\
10\% added whey protein & 0.055 \(\pm\) 0.048 & 0.026 \(\pm\) 0.013 \({}^{\ast}\) & 1.105 \(\pm\) 0.068 \\
3\% added egg white protein & 0.086 \(\pm\) 0.006 \({}^{\ast}\) & 0.012 \(\pm\) 0.002 \({}^{\ast}\) & 1.008 \(\pm\) 0.013 \\
5\% added egg white protein & 0.114 \(\pm\) 0.008 \({}^{\ast}\) & 0.023 \(\pm\) 0.001 \({}^{\ast}\) & 1.003 \(\pm\) 0.014 \\
10\% added egg white protein & 0.127 \(\pm\) 0.004 \({}^{\ast}\) & 0.024 \(\pm\) 0.002 \({}^{\ast}\) & 0.960 \(\pm\) 0.001 \\ \hline \end{tabular}
\end{table} 
Table 2: Measured results of Herschel–Bulkley model at different concentrations of added whey and egg white protein to pasteurized liquid whole eggs in comparison to the liquid whole egg control group. \({}^{\ast}\) are for significantly different groups (Tukey’s \(p\) \(<\) 0.05). The previous explained interactions and linkages also occur in egg white added-protein solutions, but more factors are involved, which contribute to more severe results. Shifting from a shear thickening to a strong shear thinning behavior when adding egg white protein to liquid whole egg can be caused by a crowding effect of the increase in total protein concentration.