## 3 Results  
To determine the most efficient PEF parameters for milk pasteurization, the _E. coli_ suspension was prepared in milk and was exposed to various electric fields by varying the number of pulses and field strength (Figures 3 and 4). From these results, we selected 20 pulses, at 24 kV/cm pulse strength, and 25 us of pulse duration as the optimal PEF parameters for further studies and for comparison with other pasteurization methods: LTLT, UHT, MF (Table 1). A significant statistical difference (\(p<0.05\)) in bacterial inactivation was achieved by comparing the results obtained with the control (Figure 3). Bacterial inactivation at a PEF strength of 5 kV/cm was equal to 970 colonies, whereas the number of bacterial colonies in the control was 9000, which corresponded to 9 \(\times\) 10\({}^{7}\) cfu/mL. Bacterial viability compared to the control decreased by 0.97 log. At pulse strengths of 10, 15, 20, and 24 kV/cm, the cfu values were 700, 680, 330, and 270, respectively, which corresponded to 1.11, 1.12, 1.44, and 1.52 log reductions in bacterial viability. Milk samples were treated with 24 kV/cm field strength by increasing the number of pulses, and the colony count was assessed based on the number of dilutions made (Figure 4). A significant decrease in bacterial viability was achieved in the samples treated with 10 and 20 pulses. The colony count in the control yielded 12,100, which corresponds to 1.2 \(\times\) 10\({}^{8}\) cfu/mL. The numbers of colonies at 10, 20, 30, 40, 50, 60, 70, 80, 90, 99 pulses were 140, 18, 7, 4, 5, 5, 6, 6, 6, 5, respectively. At these pulse numbers, bacterial viability compared to the control decreased by 1.94, 2.83, 3.24, 3.48, 3.38, 3.38, 3.30, 3.30, 3.38 log, respectively. In samples treated with UHT, bacterial activity and \(L\). _monocytogenes_ were not detected. Raw milk samples were contaminated the most, with a total bacteria count of 33.5 \(\times\) 10\({}^{4}\) cfu/mL and coliforms of 1333 cfu/mL. Comparing raw milk samples to treatment with PEF, we measured a significant decrease in coliform count at 2.4 log, while the total bacterial count decreased by 0.9 log. In the samples treated with MF and LTLT pasteurization techniques, coliform bacteria were not detected, and LTLT technology reduced the total bacterial count by 3.96 log, while 3.79 and 4.35 log reductions were observed in samples treated with MF1 and MF2. Undenatured whey protein content in raw milk samples and those treated with PEF was found to be the same; in both cases, it was 4.98 mg/mL (Figure 5). Milk samples treated with MF yielded 4.66 and 4.55 mg/mL undenatured whey protein, even though, after filtration, milk was pasteurized at 76 \({}^{\circ}\)C for 20 s (MF1) and 76 \({}^{\circ}\)C for 30 s (MF2). A significant difference in undenatured whey protein content was observed in samples treated with UHT. Samples yielded only 0.26, 0.19, and 0.51 mg/mL of undenatured whey protein, due to high treatment temperatures of 140 \({}^{\circ}\)C, at which whey proteins denaturize. Figure 4: _E. coli DH5a_ inactivation dependence on the number of pulses at 24 kV/cm voltage, after 24 h of incubation in agar plates at 37 \({}^{\circ}\)C. The abscissa shows the number of pulses used during the experiment; the ordination axis presents the mean of colony count. C—Control (raw milk). Control and PEF-treated suspensions were diluted with pasteurized (UHT) milk at ratio of 1:100. Different lowercase letters indicate significant differences between the samples (\(p<0.05\)). LTLT pasteurization yielded 1.85 mg/mL undenatured whey protein content because of the low temperatures used during processing at 63 \({}^{\circ}\)C for 30 min (Figure 5). After the effect of different pasteurization techniques on undenatured whey protein content was determined, experiments were performed to understand the effect of high-intensity electric pulses on \(\beta\)-lactoglobulin concentration, compared to traditional pasteurization techniques.