The quality of an applied protein extract is important in both serological and in vivo diagnosis of allergy, and for allergen detection methods. In the present study the effects of the extraction procedure and hazelnut source on antibody binding to hazelnut (Corylus avellana) proteins were investigated. An overnight extraction procedure in trisÁ glycine buffer at 458C was compared to a quick, vigorous extraction in a tris buffer at room temperature (RT). Antibody binding was studied by the use of polyclonal antiserum, a monoclonal antibody against the pollen-unrelated allergen Cor a 9, and human IgE from hazelnut allergic individuals. The extraction procedure, as well as the storage time and degree of processing of hazelnuts affected the protein constitution of the extract, as visualised by SDSÁPAGE. Fresh and roasted (10 min at 1708C) hazelnuts generally contained a higher amount of intact hazelnut proteins than elder ( 6 months) raw hazelnuts stored at RT. The time of storage of raw hazelnuts was inversely related to the amounts of Cor a 9 and IgE-binding proteins. In general, a rapid extraction procedure increased the efficacy of protein extraction and antibody-binding capacity to the proteins compared to an overnight extraction protocol. The present study indicates that for the production of hazelnut protein extracts, the use of fresh hazelnuts is important. A quick, vigorous extraction in a tris buffer might contribute positively, at least for extraction of Cor a 9.
A rocket immunoelectrophoresis (RIE) method is described and compared with a commercial ELISA kit. Thirteen food products were selected from the categories sausage, rice pudding, fruit-ice, biscuit and baby-dinner. These had all tested negative for casein in a previous investigation using an older commercial ELISA kit. In the present study, using a more recent commercially developed ELISA kit and RIE, only three of the 13 products still tested negative for casein. However, the RIE detected levels of casein in ten of the remaining products, whereas the ELISA revealed the presence of casein only in the three products giving the highest levels of casein with RIE. Thus, the two methods both confirm the presence of casein when the levels in the samples are within the range of the detection limit for the ELISA method.
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