## 1 Introduction  
Apples and citrus fruits are extensively consumed in many countries, and they are considered to be valuable health-promoting food as they contain biologically active components such as ascorbic acid, caroten (provitamin A) and group B vitamins, flavonoids, carotenoids, and phenolic acids, which have beneficial effects for human health [1; 2; 3; 4]. Systematic consumption of fruits and vegetables reduces the risk of civilisation diseases and also facilitates body mass control [5; 6; 7; 8]. Reports of the World Health Organisation of the Food and Agriculture Organisation recommend that adults should consume at least five of fruits and vegetables daily [9; 10]. On the other hand, cultivations of apple trees and citrus trees are attacked by numerous pathogenic fungi and by pests. For this reason, plant protection agents are commonly applied in conventional cultivations (as well as in sustainable agriculture systems), at various stages of plant development, to control pests and diseases which can cause a reduction in yields [11]. Residues of pesticides in fruits originating from such cultivations may constitute a hazard for human health [12; 13; 14].  
European Union (EU) regulations specify the maximum residue limit (MRL) for pesticides in food of plant origin [15]. In the United States (US), the US Environmental Protection Agency (EPA) approves and registers the use of pesticides and establishes the maximum level of pesticide chemical residues (tolerances) allowed to remain in or on food after treatment with approved pesticides (tolerances may be known as MRL in other countries) [16]. It should be mentioned that the values of MRL are updated on the basis of current data on the safety of application of such plant protection agents, and within the last decade, certain pesticides have been banned from use in crop plant cultivations. Incorrect use of pesticides may result in food contamination, and in consequence, cause harm to consumers, therefore it is important to monitor the level of residues of those contaminants in fruits. Knowledge of the effect of home processing on the level of pesticide residues in fruits is necessary to reduce dietary hazards.  
Numerous studies have demonstrated the presence of pesticide residues in apples and citrus fruits, and although home processing of fruits, such as cooking, frying, baking and blanching, leads to a considerable reduction in pesticide residues [17], those fruits are most often consumed with no prior processing. Apples are often eaten directly after washing, or they are peeled, but it needs to be emphasised that certain consumers eat apples even without washing them first. For apple washing under tap water to be effective, a sufficient amount of water must be used, and the duration of the washing process is also important. In model experiments, apple washing time of 2 minutes is specified [18]. However, it should be emphasised that consumers often do not wash fruits at all, or else they wash them for a notably shorter time, e.g., 5-10 s, which results from various reasons, such as the high speed of life or ecological considerations. In the case of apples, the peel can be easily removed by peeling, which will also remove most of the pesticide residues, however, important nutrients (e.g., polyphenolic compounds, fibres, pigments, vitamins and minerals) will be lost as well [18]. In the case of citrus fruits, it is routine procedure to peel them before eating, with the exception of lemons, which are often used unpeeled for spice purposes. The aim of the study was to conduct an estimation of pesticide residues in various parts of apples and citrus fruits, taking into account different aspects such as the effect of simple culinary procedures, the type of washing under tap water and peeling, and keeping in mind the compliance of fruit producers with changes in the relevant legislative regulations.