# Effect of PEF Treatment on Chosen Properties of Raw and Hot Air- and Freeze-Dried Poultry Meat
## 3 Results and Discussion
### The Influence of PEF Pretreatment on the Structure of the Hot Air- and Freeze-Dried Poultry Meat
#### 3.3.4 Color  
Figure 6 shows the differences in the colors of the hot air- and freeze-dried meat products, while the optical properties of the studied samples expressed in the CIE L*a*b* system are presented in Table 4.  
The PEF treatment did not exert any significant effect on either the a* or b* color coordinates of meat before drying. Meanwhile, the sample after being exposed to the PEF at 15 kJ/kg exhibited a decrease in brightness (L*) compared to the raw meat. [PERSON] et al. [34] noticed that the variations of the L* color parameter of raw chicken meat treated with a PEF mainly depend on the electric field strengths. In turn, [PERSON] et al. [71] reported that PEF treatment at <50 kJ/kg did not affect the color parameters of both beef and turkey meats. Furthermore, as is shown in Table 4, the PEF decreased the L* parameter of the dried meat compared to the untreated samples, regardless of the drying method. The value of the a* parameter did not change, while the b* parameter depended on both the PEF treatment and the drying method, e.g., for the pretreated HA-dried samples, the b* parameter decreased, \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Material**} & \multirow{2}{*}{**L*** (-)**} & \multirow{2}{*}{**a* (-)**} & \multirow{2}{*}{**b* (-)**} & \multirow{2}{*}{**BI [-]**} & \multicolumn{2}{c}{**\(\Delta\)E (-)**} \\ \cline{5-6}  & & & & & **Compared to** & **Compared to** \\  & & & & & **Raw Material** & **HA/FD** \\ \hline RAW & 53.1 \(\pm\) 1.9 d \({}^{1}\) & \(-\)1.9 \(\pm\) 0.4 a & 4.0 \(\pm\) 1.7 a & - & - & - \\ PEF 15 kJ/kg & 46.5 \(\pm\) 3.9 c & \(-\)2.7 \(\pm\) 0.4 a & 2.8 \(\pm\) 1.1 a & - & 7.3 \(\pm\) 3.0 & - \\ PEF 30 kJ/kg & 52.0 \(\pm\) 5.9 d & \(-\)3.1 \(\pm\) 0.7 a & 3.4 \(\pm\) 2.0 a & - & 5.3 \(\pm\) 3.4 & - \\ \hline HA & 44.4 \(\pm\) 5.2 bc & 7.2 \(\pm\) 1.5 c & 18.5 \(\pm\) 2.8 cd & 65.8 \(\pm\) 12.3 c & 19.9 \(\pm\) 2.6 & - \\ HA\_PEF 15 kJ/kg & 40.8 \(\pm\) 3.6 ab & 6.6 \(\pm\) 1.6 c & 17.0 \(\pm\) 3.5 bc & 65.3 \(\pm\) 14.1 c & 20.3 \(\pm\) 2.9 & 5.9 \(\pm\) 2.8 \\ HA\_PEF 30 kJ/kg & 38.7 \(\pm\) 5.3 a & 7.0 \(\pm\) 2.1 c & 15.8 \(\pm\) 3.8 b & 65.2 \(\pm\) 13.5 c & 21.4 \(\pm\) 3.2 & 8.2 \(\pm\) 4.1 \\ \hline FD & 81.0 \(\pm\) 7.1 f & 2.9 \(\pm\) 1.7 b & 15.2 \(\pm\) 3.8 b & 24.0 \(\pm\) 9.3 a & 31.2 \(\pm\) 4.8 & - \\ FD\_PEF 15 kJ/kg & 75.9 \(\pm\) 3.0 e & 4.0 \(\pm\) 1.5 b & 20.6 \(\pm\) 2.2 d & 35.2 \(\pm\) 5.8 b & 29.0 \(\pm\) 2.1 & 8.1 \(\pm\) 2.4 \\ FD\_PEF 30 kJ/kg & 71.2 \(\pm\) 5.4 e & 4.1 \(\pm\) 1.7 b & 20.1 \(\pm\) 1.9 d & 37.2 \(\pm\) 5.8 b & 25.3 \(\pm\) 4.1 & 11.8 \(\pm\) 3.9 \\ \hline \hline \end{tabular}  
* Mean values \(\pm\) standard deviation with different letters in the same column are statistically different (\(p<0.05\)).  
\end{table} 
Table 4: Color parameters (L*—brightness, a*—green/red color, b*—blue/yellow color) and browning index (BI), total color change (\(\Delta\)E) in comparison to raw material and to the untreated dried material. Figure 6: Macroscopic photographs of intact and PEF-treated (15 and 30 kJ/kg) poultry meat dried with hot air (HA) and freeze-drying (FD) methods. but for the pretreated FD samples, it increased in comparison with the untreated dried meat. In turn, as reported by [PERSON] et al. [72], the PEF reduced the brightness of freeze-dried strawberries compared with untreated fruits while not affecting the values of the a* and b* parameters. When comparing the optical properties of the meat dried using different methods, it was noticed that the FD meat exhibited the brightest color, which was confirmed by the highest values of the L* parameter in the range of 71.2 to 81.0 (Table 4) and the visible effect on the macroscopic photographs (Figure 6). This can be explained by uniform light reflection from the surface of the freeze-dried meat due to the presence of relatively large pores [24] as well as by mild conditions during the FD process (limited air access, low drying temperature) [73].