Methods: English walnut food extracts were made to evaluate source material, defatting, extraction fluid, and processing. Protein content was tested by Bradford and SDS-PAGE. IgE binding was determined by Immunoblotting and microtiter plate ELISA titration using sera from walnut sensitive patients.
Results: Walnut food extracts can show a more than 100 fold variability in total protein depending on the extraction process. Aqueous extraction shows the lowest total protein content and 50% glycerin with blending greatly improves the extractability of protein. Total protein correlated to the ability to bind IgE with levels below 0.3mg/mL showing negative IgE binding with moderately sensitive serum (<17kU sIgE).
Conclusions: Walnut extract IgE binding potency is dependent on the presence of glycerin during processing.