1. Laboratory of Food Chemistry, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20, B-3001 Leuven, Belgium.
2. Corresponding author. Phone: (+32)-16-321582. Fax: (+32)-16-321997. E-mail: kristof.brijs@agr.kuleuven.ac.be
3. USDA-Agricultural Research Service, Cereal Crops Research Unit, 501 N. Walnut St., Madison, WI 53705.