Why apple allergen survives processing.

In a study that will help the food industry understand the effects of processing on allergens, scientists at the Institute of Food Research (IFR) have determined how an apple allergy protein retains its potency.

Apples are the most widely grown and consumed fruit in Europe. At the same time, around one million people in Europe are allergic to apples. This is the first time that the effects of heat and the presence of sugars on apple allergens have been characterized at a molecular level. The results are published in the October issue of Allergy.

According to IFR's Ana Sancho, "In Mediterranean countries reactions to apple allergens can be as severe as to peanuts. We investigated how one important allergen stands up to processing." A team of researchers studied a lipid transfer protein (LTP) from apple peel called Mal d 3 which can cause severe symptoms, including anaphylaxis. They heated it at different temperatures, with and without the addition of sugar, and analyzed the effects on the protein structure.

Colleagues in Amsterdam investigated the impact on histamine release in the blood of apple-allergic patients. Histamine is one of the main chemicals unleashed when the immune system overproduces the antibody immunoglobulin (IgE), causing allergic symptoms. "Our study showed how tough this protein really is," says Sancho. Researchers demonstrated for the first time how Mal d 3 maintains its ability to cause allergic reactions, and the extent to which reactivity can be reduced by different processing methods.

When it was heated, the protein unfolded, but it refolded once cooled. Mild heat treatment did not alter the reactivity of the protein, but severe heat treatment (100 C) caused a 30-fold decrease in the allergenicity of Mal d 3. The presence of sugars, which results in the Maillard reaction, had a protective effect, and less allergenicity was lost. The Maillard reaction is one of the most common chemical reactions to occur during processing.

Scientists found that the protein binds to glucose, demonstrating the importance of studying allergens in context. Different food components will interact with allergens and have an impact on their stability. Some may mask an allergen so it cannot be detected, but will not actually affect its ability to cause a reaction. With a greater understanding of how food processing modifies allergens, scientists can start to generate new ways to manage them.

Further information. Ana Sancho, Institute of Food Research, Norwich Research Park, Colney, Norwich NR4 7UA, England, U.K.; phone: [phone]; fax: [phone]; URL: www.ifr.ac.uk.