Food Processing Contaminants

Food processing employs many techniques in order to ensure our foodstuffs are free of spoilage related organisms. However, these processing measures themselves may produce chemical by-products that are harmful to human health. Common processing contaminants are:
Polycyclic Aromatic Hydrocarbons (PAHs)
Nitrosamines
3-MCPD
Semicarbazide

Polycyclic Aromatic Hydrocarbons (PAHs) are contaminants, which may occur from processing operations involving heating or smoking of food products, particularly meat. PAHs also occur in the environment as by-products of incomplete combustion. PAHs are considered to be carcinogenic to humans. Studies on food residues often focus on measuring levels of the most common carcinogenic PAH – benzo[a]pyrene (BaP); other PAHs in foods are chrysene, benz[a]anthracene and benzo[b]fluoranthene. Published reports on benzo[a]pyrene in meat products indicate levels ranging from less than 0.1 to 4 ppb.

Sodium nitrite is a food preservative commonly used to prohibit Clostridium botulinum growth in cured meats and animal feed. Overcooking of meat products cured with nitrite is known to result in the production of nitrosamines. Nitrosamines are a class of compounds that are carcinogenic in a wide range of animal types. The most common target organ is the liver. The nitrosamine, N-nitrosodimethylamine, has been found in fish feed and is known to be produced by chemical reaction between a naturally occurring amine, dimethylamine, in the fish feed and sodium nitrite. Hence, maximum levels have been set for nitrate in leafy vegetables, for nitrate/nitrite in cured meats, and for nitrosamines in food contact materials.

Chloropropanols/Monochloropropanediol (3-MCPD) esters (or bound 3-MCPD) are fatty acids of 3-monochlorpropane- 1,2-diol. 3-MCPD esters were recently found in a variety of foodstuffs, particularly in refined vegetable oils and products made with refined vegetable oils. It occurs at low levels in many foods and food ingredients as a result of processing or storage conditions. 3-MCPD is most commonly found in baked goods, bread and cooked/cured meat/fish. It has also been found in baby formula and breast milk. Scientific studies have shown that it can cause cancer in animals. Because it is carcinogenic, a maximum intake guideline of 2 µg/kg bodyweight is recommended.

Semicarbazide is a contaminant that is sometimes found in foods packed in glass jars with metal lids sealed with PVC gaskets. The EU reports findings that up to 20 ppb have been detected in these food container gaskets alone. Presence of this compound is of high concern because baby foods are typically packaged in glass jars containing these gaskets in the lids. It is both a carcinogenic and genotoxic compound in test animals. The formation of semicarbazide is believed to occur as a breakdown product of azodicarbonamide, a “blowing agent” used to make foamed plastics. At this time, the European Food Safety Authority has indicated there is no need to change dietary habits because of this compound but is looking into alternative blowing agents to reduce or eliminate semicarbazide from food products. Outside of the EU, some countries use azodicarbonamide for treatment of flour in bread-making. The risk in such applications is unknown.

SEM is also considered a marker residue for Nitrofurazone (Nitrofuran), a banned veterinary antibiotic in poultry. It has been detected in poultry foodstuffs but its validity has not been confirmed. In Brazil, in 2003, SEM cases were on the rise and it was believed to be the result of illegal antibiotic use; however it was later found to be due to azodicarbonamide treated flours, used on poultry as a breading component.