Walnut Food Allergenic Extracts

Rationale: Total protein extractability and IgE binding are useful methods for determining potency of allergenic extracts.  These techniques were applied to investigate various production methods for walnut food extracts.

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.