Received for publication 12 June 1987. This research was supported by the College of Agriculture and Life Sciences, Univ. of Wisconsin-Madison, the Wisconsin Food Processors Assn., and the Illinois Agricultural Experiment Station-Urbana. We gratefully acknowledge M.S. Zuber and L.L. Darrah, Dept. of Agronomy, Univ. of Missouri-Columbia and ARS/USDA for the development of the plant material used in this experiment, and S.H. Duke, Dept. of Agronomy, Univ. of Wisconsin for supplying the conductivity meter. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact.