# Selected Antioxidants in Organic vs. Conventionally Grown Apple Fruits
## 3 Results and Discussion
(2012) [29] found no consistent, significant effects of the cultivation management (conventional vs. organic) on polyphenol concentrations and antioxidant activity in three apple cultivars (Gala, Granny Smith, and Fuji) except certain stages of fruit development. In their study, the genotype (cultivar) effects were much more evident. In the review of [PERSON] et al. (2014) [30], the authors also underlined that the content of individual phenolic compounds in the apple fruit strongly depends on apple variety. [PERSON] et al. (2012) [31] compared the concentrations of 18 secondary metabolites (hydroxycinnamic acids, flavan-3-ols, dihydrochalcones, and flavonoids) in apple fruits from organic, integrated, and two combined systems, and reported that the contents of a majority of identified compounds were highest in the organic system. The described tendency for higher contents of phenolics in organically grown crops, observed in this study as well as reported by other authors, could be explained by (a) reduced synthesis of secondary metabolites in plants fertilized with easily available mineral nitrogen in the conventional farming systems, and/or (b) increased synthesis of secondary metabolites in plants not protected with synthetic pesticides in the organic systems (increased exposure of plants to stress factors leading to intensive production of phenolics as a defense mechanism) [32; 33]. It was previously reported that, in the environments low in easily soluble nitrogen (i.e., organic orchards), plant metabolism shifts towards production of secondary metabolites such as phenolic compounds. In contrast, the use of mineral nitrogen in conventional farming was previously demonstrated to lower phenolic concentrations in fruits and vegetables [34]. In the presented study, the only exception, with no significant organic vs. conventional system-related differences identified in case of phenolic acids (sum), and with higher content of flavonoids (sum) in conventional apple fruits, were Champion apples harvested in 2018 (Figures 3 and 4, Table 4). It is well documented that the phytochemical composition of apple fruit varies greatly between different cultivars of apples, harvest time, or geographic location [4; 7]. The significant cultivar and harvest season effect on the concentration of fruit phenolics was also identified in the presented study. A number of significant interactions between the effect of these two factors on phenolics' concentrations in the fruit were also observed, i.e., (1) in the organic system, in the 2017 season, Champion cv. was characterised by the highest, while Idared cv. was characterised by the lowest content of flavonoids (sum) among the tested cultivars. In the 2018 harvest season, the contrasting results were reported--the highest flavonoids (sum) content in Idared apples, and the lowest in Champion cv.,(2) in the conventional system, in the 2017 season, there were no significant differences in the content of phenolic acids (sum) between the studied cultivars, while, in 2018, Champion was richest in phenolic acids (sum), which was followed by Gala, and then by Idared (Table 4). Chlorogenic acid was a dominating phenolic acid in the apple fruit, constituting 78-91% of the identified individual acids. This corresponds to the other authors' reports on the hydroxycinnamic acids profile of apples [26]. The described differences in the phenolic acids (sum) content in apples of tested cultivars and production systems in most cases reflected the differences in the chlorogenic acid content (Table 4). In case of other phenolic acids (gallic, caffeic, and \(p\)-coumaric), various trends in the effects of the production systems and cultivars in the two harvest seasons were observed. Gallic acid concentrations were low and consistent among cultivars in 2017, while, in 2018, a strong interaction between the production system and cultivar was identified. Champion cv.