Monika Beszterda1, Rafał Frański2. 1. Poznań University of Life Sciences, Department of Food Biochemistry and Analysis, Mazowiecka 48, 60-623 Poznań, Poland. 2. Adam Mickiewicz University, Faculty of Chemistry, Uniwersytetu Poznańskiego 8, 61-614 Poznań, Poland. Electronic address: franski@amu.edu.pl.