Abstract: Removing free protein from a liquid mixture containing the protein and a protein-polysaccharide conjugate can be a technologically difficult, expensive, and time consuming process. The procedure described herein for removing the protein from such a mixture simplifies this removal. The procedure includes contacting the liquid mixture, including the protein and the protein-polysaccharide conjugate, with a solid phase, restricted-access media material. This material at least partially binds with the protein and separates it from the liquid mixture, thereby providing a purified liquid containing at least a portion of the protein-polysaccharide conjugate and a reduced amount of the protein. The purified liquid can be collected for further processing or use. As one example, the restricted-access media material can include porous silica particles that generally allow the protein to enter, but restrict or limit access to the protein-polysaccharide conjugate.