1. Agricultural Research Service, U.S. Department of Agriculture, Vegetable Crops Research Unit, Department of Horticulture, University of Wisconsin at Madison, WI 53706
2. Department of Nutritional Sciences, University of Wisconsin at Madison, Madison, WI 53706
3. Agricultural Research Service, U.S. Department of Agriculture, Diet and Human Performance Laboratory, Beltsville Human Nutrition Research Center, Beltsville, MD 20705