Organically vs. Conventionally Grown Vegetables: Multi-elemental Analysis and Nutritional Evaluation

Vegetables are important contributors to a healthy diet, and their adequate daily intake can help prevent some of the major illnesses. The aim of the study was to examine the content of the major and trace elements in selected organically grown (OG) and conventionally grown (CG) vegetables (cabbage, kohlrabi, Brussels sprout, beetroot, carrot, potato, and onion), taken from city green markets. Multi-elemental analysis was carried out by inductively coupled plasma method with optical emission spectrometry (ICP-OES). Nutritional quality evaluation in comparison to nutritional reference values was done. In studied vegetables, Al, Ca, K, Fe (with the exception of organic kohlrabi), Mg, Na, P, S, and Zn were quantified in all samples, whereas As, Cd, Co, Hg, Se, and V were below the limit of detection for these elements. Macroelements and trace elements were found at higher concentrations in OG and CG vegetables, respectively. Differences in concentrations of studied elements between the same vegetable species produced in two agricultural systems were significant, except for beetroot (p ≤ 0.05). Principal component analysis and hierarchical cluster analysis results showed that the botanical origin had higher influence on sample differentiation than the agronomic practice, which was in accordance with the results obtained by Mann-Whitney U test. Good quality of both OG and CG vegetables in respect of nutritionally beneficial elements was observed.