The present invention is directed to a liquid heat sterilized enteral composition comprising: a protein source in an amount of 12 to 20% by weight of the composition, the protein source consisting of whey protein containing whey protein micelles and a source of casein. The inventive heat sterilized enteral composition preferably has a cysteine content of 1.2 to 2.4% by weight of the composition. The present invention is furthermore directed to a process for preparing a heat sterilized enteral composition comprising protein in an amount of 12 to 20% by weight based on the weight of the composition, said protein consisting of whey protein containing whey protein micelles and casein, which comprises the steps of: (i) Providing an aqueous solution of a protein source consisting of whey protein containing whey protein micelles and (ii) Adding a protein source containing casein; (iii) Optionally performing a homogenization treatment step; (iv) Performing a heat treatment step; (v) Optionally performing a homogenization treatment step. Finally, the invention concerns the use of a protein source consisting of whey protein containing whey protein micelles and a source of casein, for preparing an enteral composition and/or for controlling the viscosity of a liquid enteral composition, wherein the enteral composition comprises 12 to 20 weight % total protein. The invention also concerns medical uses and treatments applying or using the inventive heat sterilized enteral composition.