1. Crop Conversion Science and Engineering Research Unit, Eastern Regional Research Center, Agricultural Research Services, U. S. Department of Agriculture, 600 East Mermaid Lane, Wyndmoor, PA 19038. Mention of trade names or commercial products is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.
2. Corresponding author. Phone: 215-836-3756. Fax: 215-233-6406. E-mail: djohnston@errc.ars.usda.gov
3. Department of Agricultural Engineering, University of Illinois, 360G, AESB, 1304 West Pennsylvania Avenue, Urbana, IL 61801.