1. U. S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 E. Mermaid Lane, Wyndmoor, Pennsylvania 19038, USA
2. U. S. Department of Agriculture, Agricultural Research Service, Edward T. Schafer Agricultural Research Center, 1616 Albrecht Blvd., Fargo, North Dakota 58102, USA
3. Department of Food Science and Technology, University of California, Davis, California 95616, USA