## 4 Discussion
### Nitrates and Nitrites  
[PERSON] et al. [59] investigated a selection of the health quality parameters of 13 microgreens, including their nitrate levels. The nitrate contents in microgreens varied markedly between species. The highest mean nitrate contents were in mustard, jute and kohlrabi (4488, 5164 and 5386 mg kg\({}^{-1}\) of fresh matter--f.m.--respectively). Low nitrate accumulation (<1000 mg kg\({}^{-1}\) f.m.) was found in Swiss chard and moderate accumulation (1000-2600 mg kg\({}^{-1}\) f.m.) was determined in radish and purple basil, while high accumulation (2600-4000 mg kg\({}^{-1}\) f.m.) was recorded in coriander, green basil, komatsuna, cress, tatsoi, mibuna and pak choi. According to [PERSON] et al. [60], eleven of the seventeen microgreen species had very high nitrate concentrations. High concentrations were noted in borage, kale, beetroot, broccoli and radish, while low concentrations were noted in sunflower. These results are consistent with those reported by [PERSON] et al. [61; 62].  
The acceptable daily intake (ADI) for nitrate ions is 3.7 mg/kg of body weight, while for nitrite ions it is 0.06 mg/kg of body weight, according to experts from the World Health Organization (WHO) and the Food and Agriculture Organization (FAO) [63]. The Commission Regulation (EU) No 1258/2011 of 2 December 2011 pertaining to the maximum permissible level of nitrates in foodstuffs establishes such a value solely for selected vegetables, such as fresh and iceberg lettuce, rocket and fresh and frozen spinach [64]. The European Commission decided, in April 2023, to lower the limit values for nitrates and nitrites in food. The European Food Safety Authority (EFSA) conducted a thorough, scientific assessment prior to making this decision. The European Food Safety Authority (EFSA) set an acceptable daily intake (ADI) of 0.07 mg nitrite ion/kg of body weight per day and kept the daily allowance for nitrate ions at 3.7 mg per kilogram of body weight [65].  
The high differentiation in nitrate accumulations between microgreen species can depend on the intensity of their fertilisation, climatic conditions, the content of some macro- and micronutrients in the soil, the action of some herbicides, the fungal infestation of plants or the way the product is stored. Differences in the levels of nitrates in various parts of vegetable crops are related to both their translocation and the intensity of their metabolism, and also to genetic factors [59; 61].  
The examined microgreens of rare oilseed plants may be a source of contaminants and nitrates. The mineral profiles of these plants are mainly determined by genotype. Microgreen cultivation involves compliance with safety standards and replicable conditions to guarantee that the highest nutritional value is reached at the lowest possible contaminant level.  
The following supporting information can be downloaded at [[https://www.mdpi.com/article/10.3390/app14104298/s1](https://www.mdpi.com/article/10.3390/app14104298/s1)]([https://www.mdpi.com/article/10.3390/app14104298/s1](https://www.mdpi.com/article/10.3390/app14104298/s1)), pictures of microgreens of _Nigella sativa_ L. _Carthamus titorius_ L. and _Camelina sativa_ L. from the first and the second harvest.  
Conceptualization, T.L., J.K.-D. and B.K.; Methodology, T.L., J.K.-D., S.S. and E.J.; Investigation, E.J., J.K.-D., S.S. and B.B.; Writing--Original Draft Preparation, J.K.-D.; Writing--Review and Editing, J.K.-D., B.B., S.S. and B.K.; Supervision, T.L. and B.K.; Funding Acquisition, J.K.-D. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Science Centre (Poland), grant number 2022/06/X/NZ9/00311.  
Not applicable.  
The data presented in this study are available in article.  
The authors declare no conflicts of interest.