A new study by U.S. Food and Drug Administration (FDA) researchers has demonstrated the seafood allergen cross-contact risks of shared breading systems used in food production. The findings were published in the Journal of Food Protection.

Although it is not uncommon for foodservice and food retail businesses to use multipurpose breading mixes across animal- and plant-based foods to streamline preparation and reduce operational complexity, the allergen cross-contact risks from reusing breading mixtures has remained largely underexplored. This knowledge gap limits the scientific basis for risk assessment and the development of effective control strategies. Therefore, the present study was conducted to determine the extent to which seafood allergens can transfer to other foods through reused breading mixtures, as well as to evaluate the effectiveness of interventions in reducing allergen residues between uses.

In a laboratory experiment, the researchers separately prepared 20 batches each of shrimp and cod at 20–30 grams (g) per batch in a mixing bowl containing 200 g of breading mixture. The breading mixtures were then reused to coat chicken, mushrooms, and zucchini. ELISA kits were used to assess allergen transfer.

Both shrimp and cod proteins were found to progressively accumulate in breading mixtures as batches were prepared. However, cod proteins shed more readily and in higher concentrations than shrimp proteins during breading. After breading 20 batches of cod, allergen protein levels reached 628.7 micrograms per gram (µg/g), which is more than 18 times the levels of cod protein measured in the breading after five batches.

On the other hand, shrimp proteins accumulated more slowly, with only 17.2 µg/g detected after 20 batches. Shrimp proteins also demonstrated greater variation across locations and experiment replications than cod.

When the levels of allergenic protein were measured in subsequently prepared foods, the researchers found that shrimp posed a much lower cross-contact risk than cod. Specifically, estimated exposures due to cross-contact from breading mixtures reused after shrimp fell below 1 milligram (mg) total shrimp protein. For context, 200 mg is the reference dose for shrimp protein proposed by the Food and Agriculture Organization of the United Nations (FAO)/World Health Organization (WHO) for Codex allergen risk management guidance and risk-based precautionary allergen labeling recommendations.

Breading other foods in reused mixture after cod, however, resulted in the Codex reference dose of 5 mg total fish protein being consistently exceeded in single servings of chicken, mushrooms, and zucchini.

The researchers also assessed the effectiveness of sieving breading mixtures between batches as a control strategy to reduce allergen residues in foods. Although finer sieves with pore sizes at 75 micrometers (µm) were more effective at removing cod and shrimp allergens, sieving was unable to completely eliminate seafood allergens from the breading mixtures. Sieving also resulted in the substantial loss of usable breading mixture, suggesting impracticality for real-world use in foodservice and industrial settings. Overall, the researchers concluded that sieving alone may not be an effective allergen control measure.