Received for publication 24 Jan. 1986. Research supported by Color-Treme Co., Clyman, Wis., a Division of Beatrice Food Co., and by the College of Agricultural and Life Sciences, Univ. of Wisconsin, Madison. This investigation is a portion of a thesis presented in partial fulfillment of the requirements for the PhD degree. 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.