Abstract: The invention relates to a method and hydrolysis tank for enzymatic hydrolysis of raw materials containing collagen and proteins to produce the three layers: a top layer containing fat, a mid-layer comprising water soluble constituents and denatured collagen, and a non-soluble bottom layer comprising bones and non-soluble proteins. These layers are separated and the second layer is further separated by cooling for a time period sufficient to form two layers: a bottom layer containing partially or wholly set collagen, and a liquid top layer containing the remaining water soluble proteins which are removed. The other is heated until it becomes liquid. The hydrolysis tank comprises a turnable stirring mechanism, a device for heat exchange and a reversible screw that is arranged in the bottom of the tank. A clearing sump for separation of collagen, includes an inlet for supply of hydrolysate.