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According to Regulation (EU) 1169/2011, restaurants and catering services have to manage the risk of food allergens in the products they offer. One of the sources of hidden allergens in food could come from the cross-contact with surfaces or utensils. In order to gain knowledge about the current situation in such kind of establishments, the occurrence of 3 main allergen residues (milk, egg and gluten) has been evaluated in food-contact surfaces from 50 school canteens during a period of two academic years (2014–2016). The study included not only food-contact surfaces of general use but also surfaces for exclusive use in meals free of specific allergens. These food-contact surfaces were selected and analyzed in situ by using a rapid LFIA test during the visits to kitchens. Leftover sample was sent to a laboratory where an ELISA test was performed to confirm results. Out of 621 analyzed surfaces (213 samples for milk and egg and 195 samples for gluten) none of them were found to content milk with the rapid tests. However, the presence of egg and gluten was detected in 15 and 45% of the food-contact surfaces, respectively. The results obtained with ELISA showed also a low occurrence for milk (6%) but higher for egg (24%) and gluten (57%). It has to be highlighted that for some specific food-contact surfaces the occurrence reached up to 40%. These results indicate that the current cleaning procedures as well as the subsequent manipulation of surfaces are not enough suitable for the control of allergen residues in canteens. Besides, the presence of allergens in food-contact surfaces of exclusive-use to prepare allergen-free meals implies that cross-contaminations might happen, thus increasing the risk of hidden allergens in the final product.

In the last few years awareness for allergen management has increased among operators in the food chain. Since a small quantity of allergenic food can trigger an allergic reaction, accurate information in food product labels is essential for people who suffer from food allergy. A key point to reduce the risk of uncontrolled allergen contamination is to implement a strict and validated cleaning process. In this work a sampling method based on swabbing has been optimized with two analytical methods (ELISA and lateral flow tests) for milk and egg analysis on surfaces. Swab material, extraction buffer composition, temperature, time for recovery and the quantity of the allergen residue on the surfaces have been evaluated and a specific procedure was proposed. The new method has demonstrated a good performance to recover egg or milk proteins from two typical working surfaces (stainless steel or Formica). Egg and milk powder were detected by ELISA at a level as low as 0.04 and 0.2 μg, respectively. However, the detection level with lateral flow tests rose to 0.07 μg for egg powder and 0.6 μg for milk, depending on the kind of surface. On average, repeatability of swabbing method ranged from 18 to 32%. Both methods could be applied for validation the cleaning processes and for a routine verification after cleaning.

Colostrum addition to milk results in a reduction of the yield during cheese manufacturing. Determination of IgG levels is accepted as an evidence of this troublesome habit due to the high level of this protein in colostrum. This study shows for the first time the IgG levels in bulk ewe's milk samples from Spain throughout the year. IgG quantification was carried out by a sandwich ELISA that recognizes specifically ovine IgG. The mean value of IgG concentration obtained from 481 samples was 0.271 ± 0.253 mg/ml. In general, this value is within the range considered acceptable for mature milk according to quality payment systems. Surprisingly, a high mean concentration was obtained in samples collected in winter, 0.742 ± 0.378 mg/ml, suggesting that births were grouped in that period. These results point up that standardization of ewe's milk production has not been achieved yet. For this reason, determination of immunoglobulin levels periodically would be a good parameter to control milk quality.

Hidden allergens are an important issue at kitchens from restaurants and catering establishments when preparing allergen-free meals. Cross-contact and post-cleaning contamination are the main sources of such problems. In this study, milk, egg and gluten residues were analysed on clean food-contact surfaces to evaluate the effectiveness of cleaning and storage conditions in ten school kitchens. Results showed that using detergent with proteases, rinsing the utensils before use and wash by hand, reduced significantly the occurrence of allergens in kitchen surfaces or utensils. Some storage conditions such as keeping utensils in a cupboard or covered somehow, also protect the utensils from allergen post-contamination.