1. NIZO food research, P.O. Box 20, 6710 BA Ede, The Netherlands, Laboratory of Physical Chemistry and Colloid Science, Food Physics Group, Department of Agrotechnology and Food Science, P.O. Box 8038, 6700 EK Wageningen, The Netherlands, and Van't Hoff Laboratory, Debye Research Institute, University of Utrecht, Padualaan 8, 3584 CH, Utrecht, The Netherlands