1. Netherlands Institute for Fisheries Research (RIVO), P.O. Box 68, 1970 AB IJmuiden, The Netherlands, Wageningen University, Food and Bioprocess Engineering Group, Biotechnion, P.O. Box 8129, 6700 EV Wageningen, The Netherlands, and Friesland Coberco Dairy Foods Corporate Research, P.O. Box 87, 7400 AB Deventer, The Netherlands