Fuente: WIPO "tomato" Provided is a flavor deterioration inhibitor that, when used in a beverage, suppresses flavor deterioration caused by the storage environment, especially flavor deterioration caused by light irradiation, without adversely affecting the original flavor of the beverage. Also provided is a beverage including said flavor deterioration inhibitor. A flavor deterioration inhibitor that is for food and drink and includes a protein material having the following properties A and B is used. Alternatively, by configuring a beverage to include 10-1,500 ppm of said protein material, flavor deterioration caused by the storage environment can be suppressed. (A) An aqueous solution including a crude protein amount of 20 mass% has a viscosity of 10,000 mPa·s or less when measured at 25°C after having been heated at 80°C for 30 minutes. (B) The 0.22 M TCA solubilization is 30%-95%.