31 - Effect of the Food Matrix and Processing on the Allergenic Activity of Foods

Abstract

Food processing procedures and the food matrix can affect the structure and allergenic activity of foods in a complex manner that is poorly understood and difficult to predict. Most allergens are protein molecules and possess both linear and conformational immunoglobulin E (IgE) binding sites known as epitopes. Food processing can cause many chemical changes to food proteins that have the potential to both destroy and introduce new IgE epitopes. These include deamidation, modification by reducing sugars through the Maillard reaction, and unfolding and aggregation. Interactions with other food components, such as lipids, of plant polyphenols may also affect the structure and activity of allergens. These changes usually reduce the solubility of proteins, making them difficult to study. Food allergens can be classified according to their three-dimensional structures and biologic properties, which in part determine their stability during food processing procedures. For some protein families, such as the allergenic Bet v 1 homologs in fruit, food processing frequently results in a loss of allergenic activity. Other types of allergen, such as members of the prolamin superfamily (e.g., nonspecific lipid-transfer protein or 2S albumins) retain their three-dimensional structure and allergenic activity after severe thermal processing procedures (e.g., canning, roasting). Structurally mobile proteins (e.g., caseins from milk) do not change their shape on heating and therefore keep their allergenic activity after cooking. Much of our current knowledge of the impact of food processing on allergenicity is limited to in vitro studies, and though indicative of the impact on allergenic activity, confirmation of their clinical relevance in vivo is lacking. In addition, research has focused on the impact of food processing on elicitation of allergic reactions, and there remains a lack of data on the impact of food processing on the capacity of foods to sensitize. This will be important to address in the future to better assess the allergenic risks posed by novel foods and new manufacturing processes.