other paper product additives can be added before the solution is used to produce a paper product these other additives may contribute to different properties of the paper product to be obtained the concentration of the protein hydrolysate will suitably be in the range of from 0 1 w w to 50 w w based on total fibre weight preferably the concentration of the protein hydrolysate is in the range of from 0 3 w w to 40 w w based on total fibre weight alternatively the protein hydrolysate precipitate can as such be added to a solution containing one or more other additives to be used in the manufacturing of a paper product in another suitable embodiment the protein hydrolysate precipitate is added directly to the paper pulp where after it is thoroughly mixed with other paper pulp components preferably the protein hydrolysate additive is used in the form of a solution the present invention also relates to a process for preparing a paper pulp comprising mixing in the wet end a protein hydrolysate derived from keratin containing material with virgin and or recycled cellulose fibres and recovering the paper pulp so obtained the present invention also relates to paper pulp obtainable by such a process suitably such paper pulp comprises protein hydrolysate derived from keratin containing material in an amount in the range of from of from 0 1 to 50 wt based on total paper pulp preferably such paper pulp comprises protein hydrolysate derived from keratin containing material in an amount in the range of from 0 3 to 40 wt based on total paper pulp the present invention further relates to a process for preparing a paper product comprising mixing the wet end of a papermaking.