PURPOSE: To obtain the title composition with its bitter taste mitigated and its sweet taste got mellow, good in dissolving rate and solubility, to be used as a beverage or food additive by incorporating a water-soluble casein calcium with an α-L-aspartyl-L-phenylalanine methyl ester.

CONSTITUTION: The objective composition can be obtained by incorporating (A) a water soluble casein calcium with (B) an α-L-aspartyl-L-phenylalanine methyl ester (aspartame). For example, 10g of aspartame and 100g of a water-soluble casein calcium are dissolved in 900ml of water.