1. Laboratory of Food Chemistry, Katholieke Universiteit Leuven, Kardinaal Mercierlaan 92, B-3001 Heverlee, Belgium.
2. Corresponding author. E-mail: wim.veraverbeke@agr.kuleuven.ac.be Phone: +32-16-321634. Fax: +32-16-321997.
3. Grain Quality Research Laboratory, CSIRO Plant Industry, P.O. Box 7, North Ryde, NSW 1670, Australia.