## 3 Results and Discussion
### Effect of Peeling on the Content of Pesticides
The analysis of the levels of residues of individual pesticides in apple flesh did not reveal any instances of values exceeding the MRL in the years of the study. Accumulation of pesticides in fruits is dependent on the method of operation of plant protection agents [17]. In the case of systemic compounds, e.g., boscalid, bupirymat, cyprodini, difenokonazol, flonicamid, fluopyram, pyraklostrobin, pirymethanil, pirymicarb, tebuconazole, tachlopryd, toifanate methyl, and trifloxystrobin, they penetrate into plant tissues, due to which their concentration in peeled apples is higher and more difficult to remove through the use of technological processes. In the case of nonsystemic contact oper  
Figure 10: Content of pesticides in samples of flesh of apples from the harvest of 2020. Figure 9: Content of pesticides in samples of flesh of apples from the harvest of 2012.  
ations (e.g., deltamethrin, fluidoxonil and methoxyfenzoide), a higher level of reduction in the levels of residues is observed in fruits with the peel removed [17]. A study conducted by [PERSON] et al. [86] on the level of contamination of apples from south Kazakhstan demonstrated that 50% of the samples contained 24 pesticides at concentrations of 0.006-0.62, 0.005-0.46 and 0.02-1.38 mg/kg, in whole apples, in the flesh and in the peel, respectively. Furthermore, 26 identified compounds had concentrations higher than the MRL, primarily the insecticide chlorpyrifos in 13 samples (MRL 0.01 mg/kg), the acaricide propargite in 10 samples (MRL 0.01 mg/kg), and triazophos (MRL 0.01 mg/kg). The compounds detected in the apples represented three groups of pesticides: acaricides (2), fungicides (8) and insecticides (14), and their concentrations ranged from 0.004 to 1.38 mg/kg in the peel, from 0.001 to 0.46 mg/kg in the flesh, and from 0.003 to 0.62 mg/kg in whole apples. The highest concentrations of the identified compounds in apple peel were noted in the case of the acaricide propargite (1.38 mg/kg), followed by the insecticides triazophos (1.25 mg/kg) and chlorpyrifos (1.03 mg/kg), whereas in samples of apple flesh, lower concentrations of pesticide residues were noted relative to the apple peels, with the highest concentrations observed in the cases of propargite (0.46 mg/kg), chlorpyrifos (0.31 mg/kg), and the fungicide boscalid (0.22 mg/kg). In whole apples, the highest concentrations were identified in the cases of propargite and chlorpyrifos, at 0.62 and 0.42 mg/kg, respectively. The next most frequently identified active substance was cypermethrin (22.5% of all analysed samples), a representative of the group of insecticides, with concentrations of 0.006-0.29 mg/kg in apple peels, 0.002-0.06 mg/kg in the flesh, and up to 0.2 mg/kg in whole apples. In 22.5% of the analysed samples, another insecticides was identified--acetamiprid--with concentrations of 0.017-0.813 mg/kg in the peel, 0.003-0.134 mg/kg in the flesh, and 0.003-0.089 mg/kg in whole apples. In a study on four apple cultivars, [PERSON] and [PERSON] [73] observed significantly lower pesticide residues (below 0.05 mg/kg) in whole apples relative to the analysed samples of apple peels (0.45 mg/kg-0.77 mg/kg). Mechanical peeling, typical of home processing, and chemical peeling, used mainly in industrial processing, are treatments which significantly contribute to a reduction in the level of pesticide residues in the flesh of fruits. Most of the pesticide residues are removed with the fruit peel [87]. In this case, the systemic operation of pesticide residues is not always correlated with lower reduction in pesticide residues through peeling [87]. Our experiment demonstrated a significant effect of peeling on the content of pesticides in apples (Figures 11 and 12). Peeling allowed us to reduce the levels of pesticides, expressed in %, within the range from 24% (carbendazim) to 100% (triflumuron, thiodicarb, tebuonazole). Figure 11: Percentage reduction in pesticide residues in apples as a result of peeling in 2012.