## 3 Results and Discussion
### Comparison of Phenolic Compounds Detected in Juice of Black Chokeberry  
The results in Table 4 showed no significant difference between fresh juice and PEF juice, and again this small difference could be related to the difference in dry matter content. Growing conditions had an impact on the content of particular fractions of polyphenols. Juices obtained from samples 1-3 contained more total polyphenols. Chokeberries from cultivation 1 had the highest number of polyphenols, 2435.02 mg/100 mL, while juice from fruits from conventional cultivation had the lowest amount: 6-2139.55 mg/100 mL. As in the work of [PERSON] et al. [4], the content of individual fractions was as follows: anthocyanins \(>\) procyanidin polymers \(>>\) phenolic acids \(\geq\) flavonols \(>\) flavan-3-ols \(>\) flavanone. The content of polyphenols in fruit and later in juices is strongly influenced by atmospheric conditions. Although the plantations from which chokeberries were sourced were located in one region, there were small local differences in the number of rainy and sunny days, which was reflected in differences in particular polyphenol fractions content.  
The most important group of identified polyphenolic compounds in our juice samples were anthocyanins (seven cyanidin derivatives), which accounted for about 40% of total polyphenols (Table 4). The predominant compound was cyanidin-3-O-galactoside, whose content ranged from 543.48 to 606.36 mg/100 mL, and in PEF-treated juices from 549.98 to 616.32 mg/100 mL. It follows that PEF treatment slightly increased the content of cyanidin-3-O-galactoside analogously to the other anthocyanins.  
The second-largest group of compounds present in our chokeberry juice samples was procyanidin polymers, which accounted for \(\sim\)35% of all polyphenolic compounds. They cause the tart taste of chokeberry juices and, at the same time, constitute an important group of prohealth compounds. These compounds are also interesting for their strong antioxidant activity and health benefits, as they may have, for example, anticancer and antiproliferative effects [9].  
Another important group of compounds was phenolic acids (Table 4). Based on ultra-performant liquid chromatography techniques, five phenolic acids were identified in the samples. The dominant compound was chlorogenic acid, and its determined content in the juice samples ranged from 88.29 to 159.38 mg/100 mL in fresh juices and slightly more in PEF-treated juices: from 89.86 to 166.24 mg/100 mL. These results correspond tothose obtained by [PERSON] et al. [4] in fresh chokeberry fruit from organic and conventional cultivation. In addition, analogous correlations were reported in the study on various chokeberry fruit products by [PERSON] and [PERSON] [32]. Flavonols are another group of polyphenic compounds determined in fresh and PEF-treated chokeberry juices. Eight flavonoids were identified in the samples, including six quercetin derivatives and two isorhametin derivatives.  
Flavan-3-ols were obtained for \(\sim\)7.0% of the total polyphenic compound content in our juices. Three compounds were identified in the samples, two monomers ((+)--catechins and (-)--epicatechins) and dimer--procyanidin B2 (Table 4). The biggest content was determined for (-)epicatechin, which was fairly stable irrespective of the place of chokeberry cultivation, which the effect of PEF treatment on juice found to be insignificant.