Studies have shown that several different reaction mechanisms take place simultaneously [11]. The reaction of amino groups of proteins with α,β-unsaturated oligomers, found in commercial aqueous solutions of glutaraldehyde, yields Michael-type addition and Schiff's base product stabilized by conjugation. The reaction of monomeric glutaraldehyde with proteins could involve some dimerization leading to quaternary pyridinium compounds. In basic conditions, dimeric cyclic glutaraldehyde reacts with amino groups of protein yielding Michael's addition products. The reaction of amino groups of proteins with monomeric cyclic hemiacetal and its multimeric form, found in aqueous solutions of glutaraldehyde, yields acetals. In addition to amino groups, glutaraldehyde could react with thiol, phenol, and imidazole groups [12].