A beverage composition is disclosed that comprises a mixture of a protein hydrolysate and vitamin B2, and also contains an amount of ascorbic acid sufficient to prevent the generation of an off-flavor when the mixture is exposed to light. The off-flavor generated upon exposure to light can be reduced in accordance with the beverage composition of the present invention. Also disclosed is a method for preventing an off-flavor in a beverage composition containing a protein hydrolysate and vitamin B2, and a process for producing a beverage composition containing a protein hydrolysate and vitamin B2. Furthermore, an agent for preventing an off-flavor in a beverage composition containing a protein hydrolysate and vitamin B2, wherein the agent comprises ascorbic acid as an active ingredient is disclosed.