They are among the most consumed fruits and vegetables in the world: strawberries and tomatoes. However, many people are allergic to them, particularly people who are also allergic to birch pollen. A team from the Technische Universität München (TUM) has investigated which strawberry or tomato varieties contain fewer allergens than others and to what extent cultivation or preparation methods play a part.
The incidence of food allergies has increased in recent decades: it affects three to four percent of the adult population and five percent of children. Tomatoes (Solanum lycopersicum) and strawberries (Fragaria x ananassa) can cause allergic reactions due to the presence of various allergenic proteins.
First and foremost are proteins that resemble birch pollen, the major allergen. Because of this similarity, this all can lead to birch pollen-associated food allergy. About 1.5 percent of the population in Northern Europe and up to 16 percent in Italy are affected by a tomato allergy. About 30 percent of those who have a birch pollen allergy also claim to have allergenic reactions to strawberry fruits.
Symptoms of an immunological reaction to strawberries or tomatoes may show through the skin (urticaria or dermatitis). There may be irritated mucous membranes, colds as well as abdominal pain. Symptoms of food allergies may develop after eating fresh fruits or vegetables, while processed foods are often tolerated.
Previous studies have found that there are several proteins in both strawberries and tomatoes that can trigger allergic reactions. The aim of the two recently published studies -under the direction of Prof. dr. Wilfried Schwab of the department of Biotechnology- was to quantify an important allergy-causing protein in the different strawberry and tomato varieties.
In order to analyze a broad spectrum, in both cases varieties were chosen that differ in size, shape and color. Furthermore, the influence of the biological and conventional cultivation conditions were investigated, as well as different processing methods -from sun drying, through oven drying to freeze-drying. It was assumed that the content of the allergy inducing protein will vary with the color of the ripe fruit, the state of growth and the processing method.
The variety makes the difference
Twenty-three different colored tomato varieties and twenty strawberry varieties of different size and shape were examined, to analyze the genetic factor that expresses the allergy inducing protein in the fruits.
The content of the allergen in both crops varied greatly within the varieties. Furthermore, the heat sensitivity of the proteins could be confirmed: when the fruits were exposed to intense heat during the drying process, their allergy potential was lower. The influence of cultivation conditions (conventional and ecological) on the allergy content was low.
Consequently, the proteins studied in the studies (Sola I 4.02 for tomatoes and Fra A 1 protein for strawberries) in future may be markers for the cultivation of hypoallergenic tomato and strawberry varieties.
