Food Matrix Composition Affects the Allergenicity of Baked Egg Products

Abstract

Background: Egg allergy is common and caused by sensitization to ovomucoid and/or ovalbumin. Many egg-allergic patients are able to tolerate eggs baked into other foods, such as muffins. Although heating egg extensively reduces allergens, the effect of other food ingredients on allergenicity of eggs, or the "matrix effect," is less well studied.

Objective: We aimed to define how food matrices impact the matrix effect in egg allergenicity.

Methods: Enzyme-linked immunosorbent assay was used to quantify ovalbumin and ovomucoid in extracts from various baked egg products: plain baked egg without a matrix, and muffins baked using either wheat flour, rice flour, or a wheat flour/banana puree mix. Allergen-specific immunoglobulin E (IgE)-blocking enzyme-linked immunosorbent assays were performed using the egg product extracts on egg-allergic patient sera to determine whether the amount of extracted egg protein in each extract correlated with how well the extracts could bind patients' egg IgE.

Results: Baking eggs in any muffin matrix led to an increase in the amount of extractable ovalbumin and a decrease in the amount of extractable ovomucoid compared with plain baked egg. Compared with wheat muffins, rice muffins had more extractable ovalbumin and wheat/banana muffins had more extractable ovalbumin and ovomucoid. The egg allergens in the extracts were able to block egg-allergic patients' egg IgE.

Conclusions: Food matrices affect egg allergen availability. Patients and families should be advised that substitutions in baked egg muffin recipes can affect the amount of egg allergens in foods and potentially affect the risk of food allergic reaction.

Keywords: Baked egg; Egg IgE; Egg allergy; Matrix effect; Muffin; Ovalbumin; Ovomucoid.

Figure 1:. Baking reduces the amount of detectable major egg antigens

Measurement of the amount of extractable ovalbumin (A) and ovomucoid (B) in raw egg (n=10) and baked egg (n=4). (C) The amount of ovalbumin and ovomucoid in a pooled heated solution of ovalbumin or ovomucoid, as a percentage of the amount detectable in unheated solutions of each, expressed as a graph (left) and a table (right). p-values are displayed, **** denotes p<0.0001.

Figure 2:. The matrix effect depends on the components of the food matrix and impacts ovalbumin and ovomucoid differently

Measurement of the amount of extractable ovalbumin (A) and ovomucoid (B) in baked egg (n=10) or muffins baked with wheat flour (n=20), a 1:1 blend of wheat flour and mashed banana (n=20), or rice flour (n=20). Dotted line on both figures indicates average amount of measured antigen in raw egg. p-values are displayed, **** denotes p<0.0001.

Figure 3:. The matrix effect reduces the amount of free egg allergen available to bind egg allergic IgE

(A) Table describing clinical characteristics of egg allergic patients who contributed serum samples. (B) Averaged ovalbumin IgE dilution curves from patient numbers 1, 2, 3, and 4 after incubation with various concentrations of muffin or egg extracts, expressed as percent inhibition compared to unblocked samples. (C) Averaged ovomucoid IgE dilution curves from patient numbers 1, 2, and 4 after incubation with various concentrations of muffin or egg extracts, expressed as percent inhibition compared to unblocked samples. AUCs of each set of ELISA dilution curves were compared by ANOVA, and p-values of post-hoc pairwise comparisons are displayed in a table next to each figure, with * denoting p<0.05 and ** denoting p<0.01.