A method for preparing alkaline hydrolysates of plant proteins, which includes the following steps: 1) preparing a suspension of proteins selected from the group consisting of pea proteins, potato proteins and maize proteins, at a dry matter content of between 10 and 15%; 2) adjusting the pH, with stirring, to a value between 9.5 and 10.5 using, as the only alkaline agent, one or more alkali metal hydroxides selected from the group consisting of sodium hydroxide and potassium hydroxide; 3) heating the resulting suspension at a temperature between 70 and 80° C., for 4 to 6 hours; 4) neutralizing said heated suspension using an inorganic acid, preferably hydrochloric acid; 5) drying the neutralized suspension so as to obtain the alkaline hydrolysate.