1. Laboratory of Food Chemistry, Department of Agrotechnology and Food Sciences, Wageningen University, P.O. Box 8129, 6700 EV Wageningen, The Netherlands, Laboratory of Physical Chemistry and Colloid Science, Department of Agrotechnology and Food Sciences, Wageningen University, P.O. Box 8038, 6700 EK Wageningen, The Netherlands, and Department of Biomedical Engineering, University Medical Center Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands