1. Wageningen Centre for Food Sciences, P.O. Box 557, 6700 AN Wageningen, Laboratory of Physical Chemistry and Colloid Science, Department of Agrotechnology and Food Sciences, Wageningen University, P.O. Box 8038, 6700 EK Wageningen, Department of Agrotechnology and Food Sciences, Wageningen University, P.O. Box 8129, 6700 EV Wageningen, and TNO Quality of Life, P.O. Box 360, 3700 AJ Zeist, The Netherlands