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Review discusses contaminants in canned food

Scientists summarize literature on chemicals in can-packaged food including metals, plastic-associated chemicals, and furans; report generally low contaminant levels but a lack of non-targeted and suspect screenings; find canning steps, internal and external factors to influence contaminant levels

In a review published on September 29, 2021, in the journal Critical Reviews in Food Science and Nutrition, Jingyun Zheng, Lei Tian, and Stéphane Bayen from McGill University in Quebec, Canada, summarized the available information on contaminants in canned food (meaning they have undergone a canning process, e.g., canned meat) and can-packaged food (sold in cans but have not undergone a canning process, e.g., soft drinks).

The scientists screened the scientific literature published between 1987 and 2021 to collect information on the type, concentration, and potential sources of chemical contaminants in canned and can-packaged food, factors influencing contaminant levels, and «analytical approaches for their detection and quantification in food.» Discussed contaminants include metals, plastic-related chemicals, such as bisphenols (FPF reported here, here, and here) and phthalates (FPF reported), the biogenic amines histamine and tyramine, disinfection by-products, and furan and alkylated furans (furan derivates). Furans are volatile heterocyclic compounds that are for instance formed during sterilization. Although classified as «possibly carcinogenic to humans» by the International Agency for Research and Cancer (IARC) in 1995, maximum allowable levels in (canned) food are still missing. High doses of histamine and tyramine have also been found to be hazardous. Together with other biogenic amines, they are naturally not present in fresh food but «may be found in food products that are processed or stored under inappropriate conditions or food made from low-quality raw materials.»

The authors summarize that the concentrations of analyzed «chemical contaminants are generally low in canned and can-packaged foods and considered to be safe for consumption. Recalls related to chemical contaminants in canned food in North America, Europe, Asia, and Oceania remain rare.» However, new manufacturing processes and can coatings entering the market (FPF reported), «must be carefully managed to avoid the regrettable replacement of one material with a more toxic one.» In addition, detection of chemicals in canned food has mainly relied on targeted analysis, neglecting «unexpected» and «unknown» chemicals. Therefore, Zheng and colleagues recommend including suspect screening and non-targeted analysis in food contaminant detection. The review points out that canning steps may influence levels of some contaminants that migrate from the can, form during canning, or get into the food before canning. Both internal factors (e.g., food composition) and external factors (e.g., storage conditions, type of can coating) were reported to impact contaminant concentrations. Thus, the authors propose considering these factors when developing measures to reduce consumer exposure to these chemicals.

For all contaminants groups, the review lists the type of chemical with its concentration and the food it was detected in, as well as the digestion methods and instruments used for analysis. For metals, also the maximally allowed concentrations by country or region are summarized. Moreover, worldwide monitoring programs that have detected certain contaminants are listed together with the food type they were detected in and whether it led to the product’s recall.

Food is canned to prolong its shelf-life while maintaining its quality. Cans are typically coated with an organic layer (made from synthetic chemicals) to protect the integrity of the can and to prevent chemical reactions between the can’s metal and the food (FPF reported). Previous surveys have reported the widespread presence of  bisphenols in cans and can coatings available on the market  (FPF reported and here).

Food Packaging Forum