1. The Graduate School Experimental Plant Sciences, Laboratory of Plant Breeding, Wageningen University, P.O. Box 386, 6700 AJ Wageningen, The Netherlands; Center for Protein Technology WU/Laboratory of Food Chemistry, Wageningen University, Bomenweg 2, 6703 HD Wageningen, The Netherlands; and Wageningen Centre for Food Sciences, Diedenweg 20, 6700 AN Wageningen, The Netherlands