Influence of Food Processing, Digestion and the Food Matrix on Allergenicity & Cellular Measures of Allergenicity

The degree of processing and digestion and the impact of embedding in food matrix components could influence the way in which allergens are presented to the immune system, and thus contribute to the severity of an allergic reaction. In addition, processing, digestion and matrix effects are also of importance in diagnostic procedures, in particular when food challenges are part of the diagnostic process. Food processing, for example, thermal processing, could alter the nature of the epitopes of a protein; however, there is no general rule on how proteins respond and the type of allergen, type of food structure, and type of thermal processing may all contribute to the impact of processing. As most proteins are digested in the stomach and the intestine, the immune system is mostly exposed to digested protein. However, digestion, even with a variety of gastric enzymes, is not always sufficient to abolish the allergo-reactivity of allergens. Recently developed in vitro models of digestion (e.g., including surfactants) are improving our knowledge on digestion. Furthermore, matrix compounds such as the fat content and proteolytic and oxidative enzymes could have an effect on the allergenicity. Enzyme immunoassays and immunoblotting are often used to assess IgE binding. However, these methods do not determine whether the allergen can cause cross-linking of FcɛR1 bound IgE antibodies; for this a cellular assay is needed. Histamine release tests, CAST, BAT and mediator release from RBL cells are examples of such cellular measurements looking at cross linking of allergens while T-cell polarization assays can be used to assess the potency of an allergen to activate CD4+ helper T-cells and skew them towards a Th2 like profile. A few cellular assays are discussed more extensively and are considered crucial to providing a comprehensive analysis of the effects of food matrix and processing methods on individual allergenic proteins.