## 3 Results and Discussion
### Visual Appearance of the Fibers  
The diameters and visual appearance of the unheated fibers were examined under the scanning electron microscope. Fiber diameter distribution and average fiber diameter are shown in Figure 1. Blend A showed the smallest average diameter with 1.68 \(\pm\) 0.83 \(\upmu\)m, whereas blend D showed the largest with 4.03 \(\pm\) 1.5 \(\upmu\)m. The spun fibers of blend B showed an average fiber diameter of 2.32 \(\pm\) 0.73 \(\upmu\)m. There seems to be no clear correlation between the highest production rate and the highest fiber diameter. Although it was found that the mean values of the diameters of fibers with different contents of protein differed significantly, previous studies showed that other factors besides the protein content such as varying humidity or temperature during spinning may also be responsible [31; 35]. Because the concentration of MD DE 2 was kept constant, it was possible to form fibers from all blends. High molecular weight polysaccharides, such as MD DE 2, provide both reducing groups for the Maillard reaction and entanglement of the molecules within the fibers by increasing chain overlap which allows the formation of stable jets [22; 26]. [PERSON] et al. stated that the fiber diameter and its uniformity is strongly dependent on the quantity of the solvent [36]. The observation that the blend with the highest protein content (blend D) resulted in the highest average diameter is consistent with the results of a previous study [37]. In this study, it was stated that a higher viscosity leads to a larger fiber diameter because the viscoelastic force resists stretching and deformation of the fibers [37]. Furthermore, blend D showed the broadest diameter distribution with a standard deviation of 1.5 \(\upmu\)m. This suggests that the fibers were less uniform than the fibers from the other blends and that the proteins could not be incorporated evenly into the MD fibers which was previously observed using pea protein and maltodextrin for electrospinninging [38]. At a low polymer concentration of the spinning solution resulting in a low viscosity, the fibers can be defective due to the reduced entanglement of the polymer chains [39]. As a result, the solution jets may be more likely to break or be electrosprayed during spinning and form polymer droplets or beads. Defects in the spun mats could be detected in all samples. Blend A showed fine fibers and some large non-spun droplets with a diameter of about 140 \(\upmu\)m (Figure 2A). These were probably caused by the fast rotation of the spinneret in combination with the low viscosity of the spinning solution caused by the low protein content. At low viscosities, there is an increased risk of bead formation due to the low viscoelastic force [37]. Blend B showed several defects as well (Figure 2B). With increasing viscosity of the spinning solution, the number of beads decreased. In summary, there is an optimum viscosity for the entanglement of the polymers and the overcoming of surface tension that is important for the outcome of the electrospinning process. In this case, the number of defects should be small and the distribution of fiber diameters should be as narrow as possible. Figure 2C,D show connection zones between the individual polymer strands and Figure 2D shows relatively broad fibers. [PERSON] et al. explained these fused fibers by a too high humidity level [31]. Increasing humidity leads to a reduced evaporation of the solvent during the transfer of the jet to the collector. The lack of time to evaporate all the solvent promotes the fusion of the individual fibers. If it is impossible for the solvent to evaporate completely before the jet arrives at the collector, the fibers fuse together and form a 3D network of interconnected fibers [19]. The morphology of the fibers is also affected by other ambient conditions, such as temperature, air velocity in the spinning chamber, and air pressure [32].