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Celery is acknowledged as a major food allergen in Europe, and mandatory labeling for preprocessed foods has been implemented. However, no methods for the specific detection of celery protein in foods have been published. In the present study, a sandwich celery ELISA using polyclonal anticelery antibodies for capture and detection was developed and validated. The method has an LOD of 0.5 mg/kg in buffer; however, it is applicable only for the screening of food products because of extensive cross-reactivity with potato and carrot proteins. Using nanoLC-ion-trap MS/MS, a number of proteins in the three vegetable species were identified as candidates for causing cross-reactions due to amino acid sequence homologies. Among others, a novel patatin (Sola t 1)-like protein was detected in celery and a flavin adenine dinucleotide binding domain-containing protein (Api g 5)-like protein was identified in carrot. The utility of triple-quadrupole MS/MS for specific and quantitative analysis of celery, potato, and carrot allergens was evaluated using whole protein extracts. Several unique precursor ion-to-product ion transitions were determined for each species, suggesting the feasibility of developing an MS-based screening method to specifically detect celery allergens in foods.

Hen's egg white protein is a major cause of food allergy, and a considerable number of countries have introduced labeling directions for processed food products. To control compliance with these regulations, analytical assays for the detection of egg in manufactured foods have been developed. In this study, we have tested the performance of 3 commercially available kits for quantitative egg analysis using 6 model heat-processed foods. The 3 assays worked well under standard conditions with soluble egg white proteins, but only the kit using a denaturing-reducing extraction buffer detected egg in complex heat-treated food matrixes. The differently extracted food samples were further used to evaluate the stability and allergenicity of the egg white allergens ovalbumin, ovomucoid, ovotransferrin, and lysozyme with polyclonal anti-egg antibodies and sera of 6 patients with egg allergy. It could be shown that differences in egg protein extractability have a significant impact on the interpretation of study results.