## 4 Discussion
from Bosnia and Herzegovina [59], certain differences in observed nutritional values can be noticed. Since these countries have similar climatic conditions, this is additional evidence that the nutritional value of bee pollen depends not only on the botanical origin and climate conditions, but also on other factors, such as soil type and bee pollen collecting period and processing. Bee pollen has a specific taste and aroma, and it can therefore be unpleasant for consumers (depending on consumers' preferences). In this case, it can be mixed with other food products, such as honey, juices and jams for better acceptability [68]. According to [PERSON] et al. [69], recommended daily intake is 20-30 g, but this strongly depends on the botanical origin of the bee pollen. Therefore, knowledge of the nutritional value of bee pollen is of great importance for use in the human diet, especially as a food supplement [5]. To identify VOCs derived specifically from pollen, hand-collected pollen is preferred over the more readily obtained bee-collected pollen [70], which may contain various pollen contaminants and show alterations in VOCs due to added bee secretions and nectar. It was found that the principal constituents in the headspace of honey bee workers are aldehydes from the chain length C\({}_{9}\) to C\({}_{17}\)[71], and a variety of lower aliphatic aldehydes were found in the bee pollen headspace (Tables 3-5) dominated by nonanal. The large amounts of these compounds found in the headspace of honey bee workers suggest that they do not originate from the cuticle (lower aldehydes were found in traces). A possible source may be alkenes and alkadienes degradation caused by oxygen, heat or sunlight [72]. The oxidation of unsaturated hydrocarbons is also known from the cuticle of other Hymenoptera [73]. From the bees' headspace, these compounds can be incorporated in the lipids in pollenkit. However, their other origin cannot be excluded, but the fact that lower aldehydes (especially C\({}_{9}\)) were present in almost all bees collected bee pollen support possible contribution from the bees. The majority of compounds on the cuticle of honey bees are long-chain alkanes, branched alkanes, alkenes and esters [74]. In the bee pollen headspace, only pentadecane and heneicosane appeared in several samples as predominant compounds, indicating their plant origin than transfer from the bees, since in that case, higher abundance will be noticed in all the samples. However, hydrocarbons such as hexadecane, octadecane and heneicosene, are likely to be the key components for nestmate recognition [75]. 3-Methylbutanal, and 2-methylbutanal, known Strecker aldehydes derived from valine, leucine, and isoleucine [70], were found occasionally (particularly in _Salix_ spp., _Quercus_ spp., _A. hippocastanum_ and _T. officinal_ bee pollen headspace). Dimethyl sulfide was rarely present (only in _Malus_ spp. and _R. lutea_ bee pollen headspace) and probably produced by S-methylmethionine degradation [70]. Several benzene derivatives were found, the major ones were benzaldehyde (in all samples, particularly in _Quercus_ spp., _A. schoenprossum, T. officinal_ and _Salix_ spp. bee pollen headspace) and phenylacetaldehyde (particularly in _R. lutea_ bee pollen headspace). These compounds have frequently been found in different honey types [76]. Phenylacetaldehydecan be generated from phenylalanine by the enzyme catalysis or Strecker degradation [76]. Benzaldehyde was found in _Salix_ spp. honey [76; 77]. Terpenes found in bee pollen are probably related to plant and pollen origin. Similar as in different honey types [78], the great majority of found terpen in the samples collected in location Otocac and Senj, especially the bee pollen from _P. mahaleb_ and _P. avium_ (Tables 3 and 4), were monoterpenes, particularly linalool derivatives such as isomers of lilac alcohol or lilac aldehyde. Starting from linalool, a variety of compounds can be formed.