Nitrofurazone is one of the nitrofuran class of antibiotics. Due to its carcinogenicity, various food regulatory authorities including those in Europe and the US have banned its use in food-producing animals. These compounds can initiate tumour formation by forming hydroxylamine derivatives that cause oxidative damage to DNA.

As nitrofurans often break down rapidly, particularly in meat, making their analysis impractical, methods for detecting illegal nitrofuran treatment generally rely upon the detection of metabolites. Semicarbazide concentrations in meat products correlate with nitrofurazone dosage and this compound has therefore been considered a marker metabolite of nitrofurazone. However, semicarbazide also forms in a variety of foods not exposed to nitrofurazone by previously unexplained pathways, thus undermining its use as a metabolite marker.

Milk powder forms semicarbazide when treated with concentrated hypochlorite solutions. Hypochlorite is widely used as a sanitizer in the dairy industry and traces of the compound might be present inadvertently in milk. It is thought that the formation of semicarbazide occurs by a reaction between monochloramine and urea. This reaction is of interest because, during the processing of milk from pasture-fed cows with a higher concentration of urea, semicarbazide might form at higher concentrations than for milk from supplement-fed cows. This semicarbazide concentrate might be erroneously considered to be a nitrofurazone metabolite, thus indicating nitrofurazone abuse.

A study by Bendall¹ investigated the formation of semicarbazide under dairy product processing conditions. Hypochlorite dosed into milk on an industrial scale produced monochloramine, but without pH adjustment, did not form semicarbazide. Hypochlorite and peroxyacetic acid each produced low levels of semicarbazide in milk and whey, but only with localised high pH conditions. Dosed hydroxyurea generated semicarbazide at any pH, with the highest levels formed at high pH. It is suggested that analysis for nitrofurazone itself or for the marker metabolite 5-nitro-2-furaldehyde could have better potential for detecting nitrofuran abuse than semicarbazide.

¹ Bendall, JG (2009). Semicarbazide is non-specific as a marker metabolite to reveal nitrofurazone abuse as it can form under Hofmann conditions. Food Additives and Contaminants 26 (1) 47–56.

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