## 3 Results and Discussion
### Antioxidant Activity and Ultra-Weak Luminescence  
Antioxidant activity was tested as FRAP and ABTS, and the results are presented in Table 2. Both values were higher in fresh juices than in PEF. The highest antioxidant activity was detected in fresh juice from chokeberry 1 (ABTS--112.58 umole/100 mL and FRAP--91.12 umole/100 mL). The lowest antioxidant activity was detected in juice treated using PEF chokeberry 6 (62.00 umole/100 mL and 43.13 umole/100 mL), forming one homogeneous group with chokeberry juice 4 (87.79 umole/100 mL and 54.98 umole/100 mL). Chokeberry fruit has high antioxidant activity [31, 32], which has also been confirmed by results obtained by [PERSON] et al. [4]. PEF treatment decreased the antioxidant activity of all the juices studied, and these differences were statistically significant. This phenomenon is not fully understood. It seems that it may be related to complex interactions of various chemical compounds in juices. To date, we do not have a definitive explanation for this unsuitable link. The PEF treatment did not affect photon emission in a statistically significant way, which should be regarded as a potentially favorable phenomenon suggesting the neutrality of the PEF technology with respect to photon emission. The reasons for higher or lower photon emission in food treated using various technologies are currently difficult to ex \begin{table}
\begin{tabular}{l l l l l} \hline \hline  & **Dry Matter** & **Ash** & **Pectins** & **Tittatable Acidity \({}^{\ast}\)** \\ \hline  & & & **\%** & \\ \hline J 1 & 24.9 \(\pm\) 1.23 \({}^{\rm{e}}\) & 0.83 \(\pm\) 0.01 \({}^{\rm{b}}\) & 0.57 \(\pm\) 0.02 \({}^{\rm{c}}\) & 1.31 \(\pm\) 0.12 \({}^{\rm{a}}\) \\ J 2 & 27.6 \(\pm\) 1.29 \({}^{\rm{c}}\) & 0.80 \(\pm\) 0.01 \({}^{\rm{b}}\) & 0.59 \(\pm\) 0.01 \({}^{\rm{c}}\) & 1.24 \(\pm\) 0.11 \({}^{\rm{b}}\) \\ J 3 & 24.8 \(\pm\) 1.22 \({}^{\rm{e}}\) & 0.96 \(\pm\) 0.02 \({}^{\rm{a}}\) & 0.53 \(\pm\) 0.01 \({}^{\rm{a}}\) & 1.22 \(\pm\) 0.11 \({}^{\rm{b}}\) \\ J 4 & 23.2 \(\pm\) 1.11 \({}^{\rm{e}}\) & 0.61 \(\pm\) 0.01 \({}^{\rm{d}}\) & 0.48 \(\pm\) 0.02 \({}^{\rm{f}}\) & 0.98 \(\pm\) 0.07 \({}^{\rm{c}}\) \\ J 5 & 23.4 \(\pm\) 0.99 \({}^{\rm{e}}\) & 0.74 \(\pm\) 0.03 \({}^{\rm{c}}\) & 0.47 \(\pm\) 0.02 \({}^{\rm{f}}\) & 1.23 \(\pm\) 0.09 \({}^{\rm{b}}\) \\ J 6 & 28.2 \(\pm\) 1.32 \({}^{\rm{b}}\) & 0.73 \(\pm\) 0.02 \({}^{\rm{c}}\) & 0.38 \(\pm\) 0.01 \({}^{\rm{d}}\) & 1.01 \(\pm\) 0.03 \({}^{\rm{c}}\) \\ PEF 1 & 26.7 \(\pm\) 1.12 \({}^{\rm{c}}\),d & 0.61 \(\pm\) 0.01 \({}^{\rm{d}}\) & 0.82 \(\pm\) 0.01 \({}^{\rm{b}}\) & 1.36 \(\pm\) 0.12 \({}^{\rm{a}}\) \\ PEF 2 & 29.1 \(\pm\) 0.98 \({}^{\rm{a}}\) & 0.74 \(\pm\) 0.02 \({}^{\rm{c}}\) & 0.89 \(\pm\) 0.02 \({}^{\rm{a}}\) & 1.26 \(\pm\) 0.09 \({}^{\rm{b}}\) \\ PEF 3 & 27.3 \(\pm\) 1.05 \({}^{\rm{c}}\) & 0.83 \(\pm\) 0.01 \({}^{\rm{b}}\) & 0.58 \(\pm\) 0.01 \({}^{\rm{c}}\) & 1.21 \(\pm\) 0.08 \({}^{\rm{b}}\) \\ PEF 4 & 25.9 \(\pm\) 1.32 \({}^{\rm{d}}\) & 0.63 \(\pm\) 0.01 \({}^{\rm{d}}\) & 0.50 \(\pm\) 0.01 \({}^{\rm{e}}\) & 1.04 \(\pm\) 0.04 \({}^{\rm{c}}\) \\ PEF 5 & 26.0 \(\pm\) 0.8 \({}^{\rm{d}}\) & 0.75 \(\pm\) 0.01 \({}^{\rm{c}}\) & 0.81 \(\pm\) 0.02 \({}^{\rm{b}}\) & 1.32 \(\pm\) 0.07 \({}^{\rm{a}}\) \\ PEF 6 & 30.0 \(\pm\) 1.24 \({}^{\rm{a}}\) & 0.75 \(\pm\) 0.03 \({}^{\rm{c}}\) & 0.61 \(\pm\) 0.01 \({}^{\rm{c}}\) & 1.06 \(\pm\) 0.03 \({}^{\rm{c}}\) \\ \hline \hline \end{tabular} \({}^{\rm{a}}\)Of malic acid; mean values with different letters (a–f) within same row were statistically different (\(p=0.05\)); values expressed as mean \(\pm\) standard deviation.  
\end{table} 
Table 1: Content of dry matter, ash, pectins, and acidity of chokeberry fresh juice and juice treated using PEF. plain and assess unambiguously. This phenomenon may be related to both the so-called spontaneous and induced emission by electrons in an excited state returning to a state with lower energy, which is accompanied by simultaneous photon emission. Ultra-weak luminescence is a new technique for studying food properties.