The impact of catechin and epicatechin, total phenols and PPO activity on the Mal d 1 content in apple fruit

The most important apple allergen in Central Europe and North America is Mal d 1. Apples are a very important source of secondary plant metabolites like polyphenols in human nutrition. It is known that oxidised phenols can bind proteins. These irreversible bindings can lead to a reduced allergenicity. The most important phenols in apple are epicatechin, catechin and their polymeric structures, which have been identified as substrates of the polyphenoloxidase (PPO). The aim of this study was to analyse the influence of naturally occurring catechin and epicatechin contents in apple on the allergenicity of apple fruits. Fruits of the cultivars ‘Elstar’, ‘Diwa’ and ‘Boskoop’ were harvested and stored for 8 and 12 weeks in a cold-chamber at 2 °C. Mal d 1-, catechin-, epicatechin- and total phenol content as well as the activity of PPO were determined. Correlation analysis showed that naturally occurring catechin as well as epicatechin has no impact on the Mal d 1 content of the tested cultivars: correlation coefficient ranged from −0.203 to 0.501 for the correlation between Mal d 1 and catechin. The results further indicated that the activity of PPO is more important than the content of total phenols to reduce the Mal d 1 level. If there is a high PPO activity, Mal d 1 could be reduced even if the total phenol concentration is low.