Radmila Milačič and Janez Ščančar. Comment on recent article speciation of Cr in bread and breakfast cereals, published in Food Chemistry, (2017) 129, 1839–1843 by Mathebula, M. W., Mandiwana, K., & Panichev, N. Food Chemistry 254 (2018) 78–79.
The main sources of chromium (Cr) in human diet consist of meat, dairy products, potatoes, bread and tea. The concentrations of total Cr in these foodstuffs range in general from about 0.2 to 0.3 mg/kg (dry mass), while in tea infusions between 0.04 up to 0.42 mg/L. The consumption of foodstuffs of animal or plant origin is considered to be safe, since Cr, even if animals or plants were exposed to Cr(VI), is present in the trivalent oxidation state, as Cr(VI) has been reduced in these organisms. Despite this accepted fact, several authors recently reported the presence of Cr(VI) in plants, bread samples and teas. In these studies, the alkaline extraction of Cr(VI) with 0.1 mol/L Na2CO3 or 0.01 molL NaOH + 0.1 mol/L NH4NO3 was applied. In these investigations the total Cr was determined in the alkaline or hot water extract, prescribing the content to toxic Cr(VI). Some authors even recommended the “safe dose” of consumption of bread and breakfast cereals that would not exceed maximum acceptable concentration (MAC) of 0.003 mg Cr(VI) per kg per bw per day (half a bowl (65 g) of breakfast cereal and four slices of toasted (122 g) or untoasted bread (160 g)). Such recommendations are inadmissible and alarming. Alarming since due to the high toxicity of Cr(VI), consumption of these basic dietary items would represent a long-term chronic exposure and health threat to the majority of the human population.
In the Letter to the Editor of Food Chemistry, Radmila Milačič and Janez Ščančar emphasized the use of adequate analytical methodologies and speciation analysis in the determination of Cr(VI) in order to prevent erroneous conclusions made on the basis of artefacts of the wrongly applied analytical methodologies. With the Letter to the Editor, the authors wanted to warn Food Chemistry readers against wrongly interpreted data on Cr speciation in foodstuffs, which were based on total Cr determination without performing adequate speciation analysis.