Semicarbazide Formation in Azodicarbonamide-Treated Flour: A Model Study

Food Research Division, Bureau of Chemical Safety, Health Products and Food Branch, Health Canada, Address Locator 2203D, Ottawa, Ontario K1A 0L2, Canada.
Journal of Agricultural and Food Chemistry (Impact Factor: 2.91). 10/2004; 52(18):5730-4. DOI: 10.1021/jf0495385
Source: PubMed


Semicarbazide was previously found in foods that were in contact with rubber gaskets foamed at high temperatures with a blowing agent azodicarbonamide. Because azodicarbonamide is an approved flour additive in certain countries, we set out to ascertain if semicarbazide is formed during the baking process from flours containing that additive. The levels of semicarbazide in baking flour treated with azodicarbonamide and bread baked from such flours were determined by isotope dilution (13C15N2-semicarbazide) liquid chromatography electrospray tandem mass spectrometry (LC-MS/MS). The samples were homogenized with HCl, extracted with n-pentane, derivatized with 2-nitrobenzaldehyde, and the derivative was extracted with ethyl acetate. After solvent exchange to 10% acetonitrile in water containing 0.1% acetic acid, the samples were analyzed using a 2.1 mm x 150 mm C18 column eluted with 2 mM ammonium formate in water/methanol (40:60). Semicarbazide was formed during the dry heating of commercial azodicarbonamide-containing flours at temperatures of 150-200 degrees C reaching levels of 0.2 mg/kg. Similar levels of semicarbazide were found in the crusts of breads made from azodicarbonamide-treated flour.

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    • "This early work on SEM in packaging material prompted further studies on azodicarbonamide, which is also approved in some countries outside the EU such as the USA and Canada for use as a flour additive due to its dough-improving properties (Health Canada; FDA Code of Federal Regulations 21CFR). Azodicarbonamide in bread flour releases SEM at levels of around 200 µg/kg when treated at typical baking temperatures of 150–200° C (Becalski et al. 2004). Noonan et al. (2005) measured free SEM in commercial bread products (white, wheat, multigrain) known to contain azodicarbonamide as an ingredient, with concentrations of SEM in the products ranging from 10 to 1200 µg/kg (mean = 260 µg/kg). "
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    ABSTRACT: A comprehensive global database on semicarbazide (SEM) in foodstuffs and food ingredients is presented, with over 4000 data collected in foods such as seafood (crustaceans, fish powders), meat (beef, chicken powders), dairy products (e.g. raw milk, milk powders, whey, sweet buttermilk powder, caseinate, yoghurt, cheese), honey and other ingredients. The results provide evidence that the presence of SEM in certain dairy ingredients (whey, milk protein concentrates) is a byproduct of chemical reactions taking place during the manufacturing process. Of the dairy ingredients tested (ca. 2000 samples), 5.3% showed traces of SEM > 0.5 µg/kg. The highest incidence of SEM positive samples in the dairy category were whey (powders, liquid) & milk protein concentrates (35% positive), with up to 13 µg/kg measured in a whey powder. Sweet buttermilk powder and caseinate followed, with 27% and 9.3% positives, respectively. SEM was not detected in raw milk, nor in yoghurt nor cheese. Of the crustacean products (shrimp and prawn powders) tested, 44% were positive for SEM, the highest value measured at 284 µg/kg. Fish powders revealed an unexpected high incidence of positive samples (25 %); in this case fraudulent addition of shellfish shells or carry over during processing cannot be excluded. Overall the data provides new insights into the occurrence of SEM (for dairy products and fish powders), substantially strengthening the arguments that SEM in certain food categories is not a conclusive marker of the use of the illegal antibiotic nitrofurazone.
    Full-text · Article · Sep 2015 · Food Additives and Contaminants - Part A Chemistry, Analysis, Control, Exposure and Risk Assessment
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    • "There is abundant evidence on the formation of semicarbazide (SEM) from nitrofurazone (NFZ) (McCracken et al, 2005). Recently the confidence in SEM as an unambiguous marker residue has been questioned, due to the fact that alternative sources of SEM have been identified (Becalski et al, 2004, Stadler et al, 2004, Nooman et al, 2005). Therefore, to ensure efficient and reliable control of nitrofurazone abuse, an alternative marker analyte, which can be unequivocally linked to nitrofurazone abuse, needs to be identified. "

    Full-text · Article · Jan 2006
    • "SEM also is used as a marker for the banned veterinary drug nitrofurazone (Hoenicke et al. 2004; Pereira et al. 2004). Depending on the country, another major source of SEM may be in the crusts of breads made from azodicarbonamide-treated flour (Becalski et al. 2004). "
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    ABSTRACT: The discovery of trace levels of semicarbazide (SEM) in bottled foods (especially baby foods) led to a consideration of the safety of this hydrazine compound by regulatory agencies worldwide. Azodicarbonamide, which is used in the jar-sealing technology known as Press On-Twist Off (or Push-Twist/PT) closures for the formation of a hermetic, plastisol seal, partially degrades with the heat of processing to form trace amounts of SEM. This review has evaluated the potential toxicological risks of resulting exposure to SEM and also the benefit of the PT technology (with azodicarbonamide) in the context of possible microbial contamination. It also considers the potential impact on infant nutrition if parents come to the conclusion that commercial baby foods are unsafe. SEM shows limited genotoxicity in vitro that is largely prevented by the presence of mammalian metabolic enzymes. Negative results were found in vivo in DNA alkaline elution, unscheduled DNA synthesis and micronucleus assays. This pattern is in contrast to the genotoxic hydrazines that also have been shown to cause tumours. Carcinogenicity studies of SEM are of limited quality, show a questionable weak effect in mice at high doses, which are not relevant to human exposure at trace levels, and show no effect in the rat. The IARC has assigned SEM as Group 3, 'Not classifiable as to its carcinogenicity to humans'. Based on estimates of exposure to infants consuming baby foods (with the assumption of SEM levels at the 95th percentile of 20 ng g(-1) in all of the consumed 'ready-to-eat' foods) compared with a no observed adverse effect level (NOAEL) in developmental toxicity studies, the margin of safety is more than 21 000. Since the risk of an adverse effect is negligible, it is clear that any theoretical risk is outweighed by the benefits of continuing use of the PT closure (with azodicarbonamide blowing agent) to ensure both the microbial integrity and availability of commercial baby foods as a valuable source of infant nutrition.
    No preview · Article · Oct 2005 · Food Additives and Contaminants
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