Preparation And Potential Allergenicity Assessment Of Egg Allergens In Chiffon Cake

Egg is an important nutrition source because it is rich in essential amino acids.However,it is also one of the eight allergic food recognized by FAO,especially for children.Eggs have a very wide range of applications in food processing,such as baking foods.The baked egg products-cake can be used in clinical for desensitization therapy.Chiffon Cake is a typical and common baked egg products and often being consumed for making easily,delicious,nice color and good texture.As we known,egg allergens in chiffon cake are not only influenced by baking temperature,but also by the ingredients in cakes.Therefore,it is worthwhile to investigate the relationships between allergenicity of egg white allergens and the different ingredients in cakes,such as milk,sugars,oil and cake flour.In this work,different ingredients were added to make five groups of cake,and their digestion and allergenicity were evaluated.The experiments included making chiffon cake,extracting the soluble protein from cakes,simulating gastrointestinal digesting the cakes,and assessing allergenicity of the digestive residues.In addition,the insoluble proteins were identified.The results were described as follows.1.According to the production process of chiffon cake and the requirements of experimental design,five different groups of chiffon cake were made,marked as the normal group,without milk group,without oil group,without sugar group and without cake flour group,respectively.The sensory evaluation results showed that the normal group got the highest score,while the group without sugar got the lowest.2.To get the optimum extraction,the extraction factors of different temperature,different buffers,and different ionic strengths were tested,respectively.The extracted soluble proteins were identified by reducing,non-reducing electrophoresis and Western Blotting.The maximal extraction was in 0.1M ammonium bicarbonate solution at 60 ?.Most of the extracted soluble proteins were polymers of molecular weight above 45kDa which remained a strong antigenicity.3.The egg allergens in the five groups of cake were detected by Biokit Egg Assay kit.The recovery rate of allergens in group without sugars was the lowest,while the group without cake flour was the highest,as 2.5%and 85.3%,respectively.4.The digestibility of the chiffon cakes were evaluated by simulated gastrointestinal digestion in vitro.It was shown that the soluble proteins were resistant to be digested by gastric juice,but were easily broken down as trypsin and chymotrypsin mixture being added.Specific IgE and IgG binding capacity of digestion products were tested by Indirect Inhibition ELISA with allergic patients' sera and rabbit's sera,respectively.Results showed that the antigenicity and allergenicity of the cakes were decreased after digestion.The egg antigenicity and allergenicity in chiffon cake all reduced after gastrointestinal digestion,and the cake without sugar reduced most,while the cake without cake flour least.However,all the cakes were lower allergenic compared to the heated egg white.That's to say,cake flour and sugar,two sorts of compounds in chiffon cake,were the key factors for affecting egg allergenicity,and food matrix could affect the allergen digestion indeed.5.The precipitations,insoluble protein of chiffon cake after digestion,were identified by SDS-PAGE and Western Blotting.Insoluble precipitate still maintained strong antigenicity.