## 3 Results and Discussion
### Restructuring of CM via PEF  
However, the process described above results in comparably low and unsatisfactory \(\beta\)-carotene contents in CM. In order to enhance the amount of incorporated \(\beta\)-carotene, another PEF treatment (PEF2) for closing or restructuring of CM was tested. Extensive trials have shown that another PEF treatment alone is not sufficient for incorporation with significant amounts of \(\beta\)-carotene and closing of CM (data not shown). Hence, a combination of PEF2 and thermization was tested to restructure CM and increase \(\beta\)-carotene load. For this, suitable PEF2 parameters have to be identified first, and it was found that higher PEF intensities were required. The reason for this is explained by the PEF effect on cells. At higher intensities and also higher product temperatures, the structure of CM is more influenced by PEF with regard to disintegration and a related CM reorientation. Higher temperatures and intensities may lead to a higher degree of interruptions, resulting in higher destabilization of CM at the beginning. However, after the treatment and due to the composition of CM, a reorientation and an agglomeration occurs. Within the first trials (data not shown), it was observed that the energy level had a greater influence on the agglomeration of CM than the electric field strength. Therefore, the electric field strength was kept constant at 15 kV/cm and specific energy and inlet temperature were varied. In combination with different thermization times, PEF2 parameters and \(\beta\)-carotene content are shown in Figure 7.  
\begin{table}
\begin{tabular}{c c c c c c} \hline  & **Control** & \multicolumn{4}{c}{**PEF1-Treated**} \\
**t\({}_{\text{therm}}\)** & **15** & **0** & **15** & **30** & **45** \\ \hline surface potential (mV) & \(-663\pm 28\) & \(-638\pm 26\) & \(-565\pm 29\) & \(-473\pm 29\) & \(-407\pm 31\) \\ \(\beta\)-carotene content (\(\mu\)g/100g) & \(<\)5 & \(<\)5 & \(-22\pm 5\) & \(-0.24\pm 6\) & \(-51\pm 5\) \\ \hline \end{tabular}
\end{table}
Table 1: Surface potential and \(\beta\)-carotene content of CM after different incubation times at 60 \({}^{\circ}\)C (t\({}_{\text{therm}}\)) with and without PEF1 treatment (control).  
It was found that a combination of PEF2 treatment and incubation time at 60 \({}^{\circ}\)C lead to significantly higher amounts of incorporated \(\beta\)-carotene and shorter incubation times compared to the application of PEF1 and thermization alone; thermal treatment could be decreased to 5 or 10 min and \(\beta\)-carotene content could be increased by at least 10 times (see dashed line in Figure 7 representing \(\beta\)-carotene content after PEF1 and thermization for 45 min). Thus, a maximum \(\beta\)-carotene in CM of 475 \(\upmu\)g/100 g was found for the application of PEF2 (E = 15 kV/cm, W = 39.5 kJ/kg, Tin = 45 \({}^{\circ}\)C, pulse width = 15 \(\upmu\)s) and subsequent thermal treatment for 10 min. The recovery rate for this procedure is 78%. In comparison, the recovery rate for disintegration via PEF1 followed by a thermization process of 45 min (cf. Table 1) is only 22%.  
As already described in the introduction, other studies to incorporate \(\beta\)-carotene into CM have already been performed. For this, [PERSON] et al., 2017, used native CM and found recovery rates of 79%, whereby 94% of it was associated with the native CM [5; 36]. [PERSON] and [PERSON], 2013, obtained recovery rates of up to 35% \(\beta\)-carotene using spray-dried casein powders [13]. Other studies used caseinate and a self-assembling procedure to incorporate \(\beta\)-carotene; [PERSON] et al., 2014, obtained up to a 62% recovery rate [14] and [PERSON] et al., 2013, determined a total extraction yield of 60% [41]. Compared to the results of these laboratory studies, recovery rates for the technical-scale PEF encapsulation technique presented in our study are comparably high.