Comparison and Functional Evaluation of the Allergenicity of Different Hazelnut (Corylus avellana) Protein Extracts

This paper investigates two methodological issues of hazelnut protein extraction: the use of protease inhibitors during protein extraction and the effect of defatting hazelnuts before protein extraction. Different protein extracts from hazelnuts were analysed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and IgE-immunoblotting to evaluate the presence of allergens in the extract. The allergy-provoking potential of these extracts was assessed by the Basophil Activation Test. This functional test relies on in vitro stimulation of human basophils from hazelnut-allergic patients with the different extracts. SDS-PAGE and IgE-immunoblot analysis of hazelnut extracts prepared without protease inhibitors revealed partial degradation of the proteins in the extracts. This observation was confirmed by the Basophil Activation Test, as the percentage of activated basophils was lower as compared to extracts prepared with protease inhibitors. Biochemical and functional evaluation of a defatted hazelnut extract did not reveal differences in comparison with non-defatted extracts. This study is the first to report on the use of the Basophil Activation Test applying human basophils for functional evaluation of protein extracts from hazelnuts. The results demonstrate that the use of protease inhibitors during extraction is essential for the stability and functionality of a protein extract, whereas defatting does not affect the quality of the protein extract.