Impact of thermal processing time and cookie size on the detection of casein, egg, gluten and soy allergens in food

Thermal processing can affect allergen detection by inducing chemical modifications as well as changes to protein structure and solubility. The objectives of this research were to investigate the effects of baking time, temperature profile and cookie dimensions and weight on the detection of four allergens (casein, egg, gluten and soy) simultaneously incurred in a non-wheat flour cookie using enzyme linked immunosorbent assay (ELISA) and flow cytometry. In general, allergen recovery decreased as baking time increased and cookie size was decreased. Temperatures at the center of the cookies also increased with decreasing cookie size and increasing baking time. Casein recoveries were: 88 to 35%, 77 to 21%, and 75 to 19% with the Ridascreen ELISA kit, Veratox ELISA kit and flow cytometry, respectively. Egg recoveries were: 48 to 8%, 4 to 0% and 5 to 0%, with the Morinaga ELISA kit, Veratox ELISA kit, and flow cytometry, respectively. Gluten recoveries were: 93 to 31%, 72 to 27% and 75 to 21%, with the Ridascreen ELISA kit, Veratox ELISA kit, and flow cytometry, respectively. Finally, soy recoveries were: 33 to 1%, 1 to 0% and 21 to 0%, with the Veratox ELISA kit, ELISA systems kit, and flow cytometry, respectively. No recoveries were obtained for soy and egg in some of the thermally processed samples. ► ELISA and flow cytometry detected casein, egg, gluten and soy in baked cookies. ► Allergen recovery decreased with increasing baking time and decreasing cookie size. ► Size and baking time influenced the internal temperatures of the baked cookies. ► False negative results for soy and egg were obtained in some baked samples. ► Thermal processing can result in inaccurate and false negative allergen detection.