1. Department of Food Science and Human Nutrition, Iowa State University, Ames, IA 50011.
2. Department of Agronomy, Iowa State University, Ames, IA 50011.
3. Department of Agricultural & Biosystems Engineering, Iowa State University, Ames, IA 50011.
4. Present address: Thermo Electron Corporation, Madison, WI 53711.
5. Corresponding author. Phone: 515-294-9688. Fax: 515-294-8181. E-mail: pjwhite@iastate.edu