A cowpea glubulin isolate was treated with protein kinase, and the functional properties of the reaction product were compared with those of a native protein isolate in the range pH 3-8. The phosphorylated proteins significantly exhibited (p less than or equal to 0.05) increased solubility in the range pH 4-6, but the solubility at pH 3, 7, and 8 was significantly (p less than or equal to 0.05) decreased when compared to that of the native proteins, The emulsifying activity index was significantly (p less than or equal to 0.05) decreased, but the emulsion stability of the proteins was generally increased (p less than or equal to 0.05) over the pH range investigated due to phosphorylation, The foaming capacity and foam stability were each signinificantly (p less than or equal to 0.05) increased in the range pH 4-6 and at pH 4 and 5, respectively, as a result of phosphorylation.