Background: Ingested cereals and inhaled cereal dusts can cause IgE-mediated allergy. Testing for these allergies yields variable, often undependable results, which could be due to the use of unsuitable or degraded testing materials.
Objective: We studied the effect of storage media, time and temperature on the stability of protein allergens extracted from wheat, rye, barley and oats flour. We also examined the effect of heat processing similar to that used when preparing foods on the stability of allergenic proteins present in wheat flour.
Methods: After storage experiments proteins in allergen extracts were separated using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and then visualized using immunoblotting or staining with Coomassie brilliant blue. After heat processing wheat flour proteins were extracted and their IgE-binding capacity was estimated.
Results: Extracted proteins from wheat, rye and barley flour appeared stable for at least 21 months when stored at 4 degrees C in an aqueous solution containing 50% glycerol and 0.45% sodium chloride. In a medium with 0.4% phenol and 0.9% sodium chloride degradation of many proteins became apparent already after 1 month of storage. Oats extracts lost their IgE-binding capacity more rapidly and the maximal storage time appeared to be 10 months at 4 degrees C in a solution containing 50% glycerol and 0.45% sodium chloride. The IgE-binding capacity of the allergenic proteins decreased as heat-processing temperature and heating time increased. No processing conditions entirely abolished IgE-binding.
Conclusion: Cereal allergen preparations can be stored either in lyophilized form or at 4 degrees C in 50% glycerol. Unheated materials should be used also when testing for food allergy, as heating reduces allergenicity and thus sensitivity at testing.