Do Food Preparation Methods Affect Allergies?

One of the interesting aspects of food allergy is that the allergenicity of particular foods may change with the method of food preparation. Knowledge of how specific food allergens are modified (weakened or enhanced) is helpful in guiding patients. A new article, "Effects of Daily Food Processing on Allergenicity,"^[1] is a welcome addition to the medical literature and a helpful reference in practice.

The processing method, the chemical structure of an allergen, and the pattern of sensitization of a particular group of atopic subjects all have a bearing on the processing effects on food allergenicity. For a thorough review and helpful tables, the article should be studied, but here I will review some of the examples described.^[1]

Peeling

Common fruits with edible skins, such as peaches,^[2] have a much higher concentration of the lipid transfer protein (LTP) in the peel (250-fold higher) than in the pulp, so peeling the skins of fruits enables most patients to tolerate the rest of it.

Boiling

Even after being boiled extensively, most lentil, pea, chickpea, and green bean allergens seem to remain intact. Regarding peanuts, the picture is more complex. The lower prevalence of peanut allergy in China (but not in Chinese immigrants eating a Western diet) has been attributed to boiling of peanuts as opposed to other thermal methods. Studies implicate leaking of the allergen from the peanut into the boiling water as an explanation for the reduced allergenicity of boiled peanuts^[3] as well as cashews.^[4] In both fish and shellfish, the major allergens (Gal c 1 and tropomyosin, respectively) are resistant to boiling.

Baking

Baking, which tends to reach higher temperatures than boiling, enables many egg- and milk-allergic patients to tolerate these foods. To some degree, this occurs with wheat as well, most notably in baker's asthma patients who react to the aerosolized raw allergens but can typically eat the product of their work.

Frying

Whether it is peanuts, tree nuts, beef (alpha gal allergens), fish, or even frog legs, most studies of frying have shown that the food allergens are preserved.

Roasting

This involves dry heating up to 200° C, typically done with nuts and seeds. Of note, roasting has been shown consistently to increase immunoglobulin E binding of peanut allergens (including the major allergens Ara h 1 and Ara h 2). Even more striking is that roasting may even increase the function of Ara h 2 as a trypsin inhibitor, essentially preserving the integrity of itself and other allergens. As for tree nuts, the allergens are mostly preserved, with a notable exception of birch allergy-related hazelnut-allergic patients (sensitized to Bet v 1) as opposed to those sensitive to the hazelnut allergen Cor a 1.

Pressure Cooking

Conventional pressure cookers (which reach a maximum of 121° C and 15 psi) do not degrade most allergens sufficiently (with the possible exception of cashew).

Microwaving

Studies show that microwaving does not reduce the allergenicity of wheat, legumes, or nuts.

Summary

Certain methods of thermal food preparation affect the allergenic properties of specific foods, especially:

Peeling of fruits and vegetables (most patients with LTP-allergy); and
Baking of egg or milk (in some patients) only after challenge in an appropriate supervised setting.

My Take

Within the same patient, allergic reactions to the same food item may vary, in part due to methods of food preparation. For many patients, other cofactors (eg, exercise, overheating, nonsteroidal anti-inflammatory drugs/alcohol ingestion, viral infections) affect the degree of anaphylaxis.

Comments

Commenting is limited to medical professionals. To comment please Log-in.

Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.