Shrimp and Cod Allergen Transfer to Non-seafood via Reused Batter and Persistence after Deep Frying

Reused liquid batter systems in retail food-establishment represent a potential yet poorly studied source of seafood allergen cross-contact. This study quantified the accumulation of shrimp and cod proteins in a liquid batter across 20 sequential preparation batches, each representing a single portion (20-25 g), and evaluated their transfer to subsequently prepared chicken, mushroom, and zucchini, both before and after deep frying at 180°C. Allergen concentrations were measured using four commercial ELISA kits (two kits per species). Shrimp protein concentrations increased about 7-fold between batches 5 and 20, while cod protein concentrations increased approximately 3-fold over the same interval. Overall, cod residues accumulated in the batter at substantially higher levels than shrimp across all batches. Shrimp and cod proteins were detected in all three non-seafood items following preparation in the reused batter. Frying reduced detectable allergen levels by 1-67% for shrimp and 74-88% for cod. Consumer exposure estimates for shrimp did not exceed the 200 mg reference dose in any food type before or after frying, whereas cod exposure exceeded the 5 mg fish-protein reference dose even at the 25^th percentile of consumption across all food types. These findings demonstrate that seafood allergens accumulate and transfer readily in reused liquid batter, posing a potential allergic risk in cross-contacted products even after frying.