The sterile filtration is performed via a validated process. The raw material passes a series of filters with decreasing pore sizes. The last filtration step is done with a sterile filtration of serum. (Pore size on request) With a chromatographic method (affinity chromatography) the antibodies in the serum are near-completely removed (< 5 μg/ml). The biological activity of the serum is not affected. All the sera is EU approved or USDA approved.