## 3 Results and Discussion
### Vitamin C Content  
Among berries, the blackcurrant possesses the greatest vitamin C content, ranging from 120 to 280 mg/100 g f.w., depending on the place of cultivation and variety. In Poland, wild rose fruits are the only plants that are superior to blackcurrant in terms of vitamin C content [2; 8; 27]. Vitamin C is very sensitive in comparison to other vitamins, and at the same time, is the least durable upon exposure to oxygen, UV radiation, pH or heavy metal ions, and is highly sensitive to damage by temperature and the time of exposure of the factors mentioned above [28]. Therefore, optimal antioxidant properties are found in the raw form. However, due to their low shelf life and the fact that they are a seasonal fruit, blackcurrants are usually eaten in processed form. It is worth mentioning that despite the processing and decreasing of antioxidant properties, blackcurrant preserves are still one of the best sources of antioxidants [16]. The average vitamin C content in blackcurrant fruits from the organic cultivation system is significantly higher, 138.85 mg/100 g f.w., than those from the conventional cultivation system, 128.68 mg/100 g f.w. The results obtained by [PERSON] et al. [29] confirmed that blackcurrant fruits are the richest source of vitamin C among all berries. Their results achieving the highest value in 'Malling Juel' (141.4 mg/100 g f.w.), followed by 'Ben Sarek' (132.6 mg/100 g f.w.). In order to analyze the content of this compound in more detail, it is necessary to examine fruits that are developed under similar, or preferably identical, conditions of the external environment. [PERSON] et al. [15] determined vitamin C content by evaluating varieties of currants cultivated in a conventional system at an average level of 109.75 mg/100 g of f.w. [PERSON] et al. [23] found no correlation between organic vs. conventional farming system for 'Ben Adler' and 'Titania' varieties, where the average vitamin C content for the conventional system was 188 mg/100 g f.w. and 103 g/100 g f.w. for 'Titania', and in the organic system, 88 mg/100 g f.w. and 107 mg/100 g f.w. The authors noted that the cultivar 'Titania' was characterized by the lowest vitamin C content of all assessed cultivars (apart from the above-mentioned ones, in addition to 'Ben Lomond', 'Pamyati Vavilova', 'Intercontinental', 'Karri', 'Askar' and 'Mairi')--regardless of the year of cultivation and production system. [PERSON] et al. [30] showed negative correlation between the content of phenolic compounds and insolation in June and July. Temperature and sunshine in late spring and summer were also negatively correlated with the concentration of vitamin C, while rainfall in summer was strongly positively correlated with the concentration of this vitamin. These results show that the most favorable conditions for obtaining blackcurrant fruits with a high content of phenolic compounds, anthocyanins and vitamin C are those with cool temperatures and heavy rainfall.  
PCA displays a strong correlation for the cultivation system and currant varieties. Overall, 69.3% can be explained by PC1 and PC2 (Figure 4). The degree of dependence between blackcurrants from organic cultivation and factors, such as dry matter, total phenolic acids, chlorogenic acid, ferulic acid, myricetin, delphinidin-3-O-glucose, cyanidin-3-Oglucose, cyanidin-3-O-rutinoside and delphinidin-3-O-rutinoside compounds content, are particularly important. Researchers showed significant differences in the concentration of anthocyanins depending on the variety; their average content in fruit was 467 mg/100 g f.w. PCA showed a strong dependence toward the cultivation system and currant varieties.