The invention concerns a method for preparing modified whey comprising steps which consists in: a) lactose removal, b) hydrolysis, c) pre-treatment of calcium trap proteins, d) hydrolysis of the pre-treated proteins and e) enzyme inactivation. The hydrolysis process is carried out in the presence of at least an endopeptidase and of at least an exopeptidase. The invention also concerns whey obtainable by said preparation method characterised in that it comprises a lactose content between 10 and 50 wt. % of the weight initially present and an amount of total proteins representing not more than 80 wt. % of the weight of proteins initially present. The invention further concerns the use of said modified whey as bread-making enhancing agent and products containing same.