Egg White Food Ladder: Evaluation of Cooking Effect on Hen's Egg White

Abstract

Egg White Food Ladder: Evaluation of Cooking Effect on Hen's Egg White Purpose: Hen’s egg white (HEW) is the most common cause of food allergy in children which induce mild to fatal reactions. The resolution of HEW allergy is delayed and the mostly recommended management is a proper elimination diet. A uniformed strict elimination diet can lead to malnutrition and decrease the quality of life of children and family, therefore, the consultation for a minimal restriction is important in HEW allergy. In this study, we aimed to identify the changes in HEW allergenicity using diverse cooking methods commonly used in Korean dishes. Methods: Crude extract of raw and 4 types of cooked HEW extracts were produced and used for SDS-PAGE, ELISA, and ELISA inhibition assays using sera from HEW allergic and tolerant children. Extracts were prepared; scrambled without oil for 20- 30 seconds in frying pan without oil, boiled at 100℃ for 15 minutes, short-baked at 180℃ for 20 minutes, and long-baked at 45℃ for 12 hours with a gradual increase in temperature up to 110 °C for additional 12 h, respectively. Results: In SDS-PAGE, the major protein bands of raw HEW were clearly observed in 14, 36-48, 50-54, and 98 kDa corresponding to major HEW components. The intensity of bands corresponding to 50-54 kDa decreased by boiling and baking. All bands were almost disappeared in long-baked egg. The intensity of the ovalbumin (OVA) IgE bands did not change after scrambling; however, an evident decrease was observed in boiled EW. In contrast, ovomucoid (OM) IgE bands were darker and wider after scrambling and boiling. The IgE binding reactivity to all EW allergens were weakened in short-baked EW and considerably diminished in long-baked EW. In immunoblot analysis, IgE strongly bound to all major EW allergens in raw EW. In individual ELISA analysis using OVA+OM+ sera, the median of specific IgE OD values was 0.435 in raw EW, 0.476 in scrambled EW, and 0.487 in boiled EW. Conversely, it was significantly decreased in short-baked (0.406) and long-baked EW (*P < 0.05). In ELISA with OVA+OM– sera, the medians of specific IgE OD values were considerably decreased in all types of cooked EWs. Significant inhibition was observed using four inhibitors: raw HEW (IC50 = 0.24 ug/mL), scrambled HEW (IC50 < 0.1 ug/mL), boiled HEW (IC50 < 0.1 ug/mL), and short-baked HEW (IC50 = 0.38 ug/mL), but there was no significant inhibition by long-baked HEW (IC50 > 100 ug/mL). Conclusion: We identified minimally reduced allergenicity in scrambled EW and extensively decreased allergenicity in long-baked EW comparing to boiled and short-baked EW as well as raw EW proteins. By applying the results of this study, we would be able to provide safe and higher quality of dietary guidance to egg allergic children. Keywords: Egg white proteins; Food allergy; Cooking; Allergenicity