Abstract: The invention relates to biotechnology. It concerns a partial hydrolysate whey proteins which contains no residual whole proteins characterized in that it contains peptides spread over the following distribution, as a function of their molar mass:______________________________________ Proportion by weight Molar mass (as g peptides per (g per mole) 100 g total peptides) ______________________________________ MM>5000 0-5 5000>MM>3500 15-25 3500>MM>1500 20-30 1500>MM>500 35-45 MM<500 5-10 ______________________________________as well as the free amino acids; the free amino acid content of the hydrolysate being less than 10% (calculated as grammes of nitrogen per 100 grammes of total nitrogen), as well as an enzymatic product for its preparation:Application to the production of dietetic milk foods.