Allergenicity of apple allergen Mal d 1 as effected by polyphenols and polyphenol oxidase due to enzymatic browning

Birch pollen-related apple allergy affects up to 5% of Germany's population due to Mal d 1. It has been hypothesized that apple allergenicity decreases by cutting, due to oxidation reactions of polyphenols with apple allergens. In this study, the influence of enzymatic browning on the allergenicity of apples was investigated by determining the total phenolic content, polyphenols, Mal d 1 and the activity of polyphenol oxidase in six different apple cultivars. Additionally, it was analysed how chlorogenic acid, caffeic acid and epicatechin combined with PPO affect rMal d 1 in vitro. Outcomes have shown that enzymatic browning led to a significant stronger decrease of Mal d 1 in Dulmener Rosenapfel, Ontario and Roter Boskoop compared to Braeburn, Golden Delicious and Granny Smith due to their stronger decrease in total polyphenols. High PPO activity may also reduce Mal d 1 allergenicity, even when the content of total polyphenols is low, as shown for Golden Delicious. The effect of PPO could be increased by naturally occurring contents of chlorogenic acid and caffeic acid as demonstrated in vitro. These results will be important for the breeding of apples with lower allergenicity.