1. Nestlé Research Center, Nestec Ltd., Vers-chez-les-Blanc, 1000 Lausanne 26, Switzerland, Toxinology and Food Safety Research, AgResearch Ruakura, Hamilton, Waikato, New Zealand, Department of Chemistry, University of California, Irvine, California 92697-2025, and Environmental Toxicology, University of Konstanz, D-78457 Konstanz, Germany