Document Type : Original Research Paper
Slovak University of Agriculture in Nitra, Tr. A Hlinku 2, 949 76 Nitra, Slovak Republic
Onion (Allium cepa L.) is widely used around the world and it is very important vegetable in the Slovak Republic (SR). Six varieties of onion (Karmen, Kamal, Amika, Hector, Diamant, White Dry) were studied and the contents of selected heavy metals, their polyphenol contents as well as the possible correlations among selected heavy metals in soil and onions were analysed. Six soil sampling sites were selected and the analyses of pH/KCl, P, K, Mg and certain heavy metals (as total and mobile fraction) were provided. The concentrations of minerals and heavy metals were determined by atomic absorption spectrophotometry and the content of total polyphenols was estimated by Folin-Ciocalteau reagent.
Results revealed the excess in maximum amounts for total Cd content, where values ranged from 0.90 to 1.24 mg/kg as well as for mobile form of cadmium and lead where values were in the range 0.06 – 0.14 mg/kg and 0.6 – 1.07 mg/kg, respectively. The content of three metals (Cr, Cd, Pb) in the dry matter (DM) of the onions exceeded the limits set by the European Union and Food Codex of Slovak Republic. Polyphenols concentration varied in the range from 162.84 mg/kg (white variety Diamant) to 1387.89 mg/kg FW (red variety Kamal).
Among the varieties statistically significant differences (P < 0.05) in intake of heavy metals and in the content of polyphenols were found.