Effect of the Strawberry Genotype, Cultivation and Processing on the Fra a 1 Allergen Content

Summary

Birch pollen allergic patients show cross-reactivity to vegetables and fruits, including
strawberries (Fragaria × ananassa). The objective of this study was to quantify the level of the
Fra a 1 protein, a Bet v 1-homologous protein in strawberry fruits by a newly developed ELISA,
and determine the effect of genotype, cultivation and food processing on the allergen amount.
An indirect competitive ELISA using a specific polyclonal anti-Fra a 1.02 antibody was established
and revealed high variability in Fra a 1 levels within 20 different genotypes ranging from 0.67
to 3.97 μg/g fresh weight. Mature fruits of red-, white- and yellow-fruited strawberry cultivars
showed similar Fra a 1 concentrations. Compared to fresh strawberries, oven and solar-dried
fruits contained slightly lower levels due to thermal treatment during processing. SDS-PAGE and
Western blot analysis demonstrated degradation of recombinant Fra a 1.02 after prolonged (>10 min)
thermal treatment at 99 ◦ C. In conclusion, the genotype strongly determined the Fra a 1 quantity
in strawberries and the color of the mature fruits does not relate to the amount of the PR10-protein.
Cultivation conditions (organic and conventional farming) do not affect the Fra a 1 level, and seasonal
effects were minor.