In the United States peanut is one of the most important sources of food allergens. Similarly, celery is a relevant allergenic food in Western Europe. Severe allergic reactions are common for both foods, and due to cross-contaminations of celery and peanut free foods during production processes unexpected allergic reactions can occur.

We monitored in co-operation with a manufacturer of celery and peanut aromas and flavorings, the cleaning process of a dispersing machine in regard to contaminations of follow-up products with celery and peanut compounds. Washing water samples taken after different cleaning steps and follow-up products were analyzed for the presence of celery and peanut traces with a celery-specific real-time PCR and a peanut-specific sandwich ELISA. PCR and ELISA results were compared with an unspecific protein assay to evaluate whether the detection of protein traces can be a fast and cost-effective method for monitoring the effectiveness of wet cleaning procedures.

In all washing-water samples taken during the pre-wash process celery and peanut residues were found. After acidic and alkaline cleaning the washing water samples and also the follow-up products were tested negative for both peanut and celery. Results of the peanut and celery specific methods were comparable with the results obtained by the protein assay.

The quantification of total protein in washing water was suitable for monitoring the cleaning process and furthermore our study revealed evidence that in cases where wet cleaning is applicable allergenic traces can be removed with high efficiency.