The present invention is directed to a heat sterilized composition comprising: a protein source in an amount of 5 to 20% by weight of the composition, said protein source comprising hydrolyzed protein； wherein the protein source has been treated in a continuous process with at least one endopeptidase, typically for a finite length of time. Furthermore, the invention concerns a heat sterilized high protein composition having low viscosity and being devoid of bitterness, comprising hydrolyzed heat sensitive protein source having a degree of protein hydrolysis in NPN/TN of 20 to 50% and at least one heat inactivated endopeptidase. The present invention is furthermore directed to a continuous process for preparing a heat sterilized composition which comprises a protein source containing hydrolyzed protein, the process comprising the following steps: (i) Providing an aqueous solution of a protein source； (ii) Performing a continuous hydrolysis step wherein the aqueous solution of a protein source is treated with at least one endopeptidase by heating at 40 to 90°C and for a finite length of time of 2 to 20 minutes； (iii) heat inactivation of the endopeptidase. The invention also concerns a method of controlling viscosity and preventing bitter taste of a heat sterilized high protein composition, the method comprising providing an aqueous solution of a protein source and continuously hydrolyzing the aqueous solution of a protein source with at least one endopeptidase prior to heat inactivation of the said endopeptidase. Finally, the invention concerns the use of hydrolyzed protein prepared in a continuous process as described herein by treatment with at least one endopeptidase for a finite length of time, for preparing a heat sterilized composition and/or for controlling the viscosity of a liquid composition, wherein the composition comprises 5 to 20 weight % total protein. The invention also concerns medical uses and treatments applying or using the inventive heat steriliz
