a process for the aseptic concentration of collagen from about 0 . 25 % suspensions to gels of 15 % using vortex flow filtration with a variety of membrane types -- ultrafiltration and microfiltration and polymeric and stainless steel is provided . the resulting gels are suitable for use in medical products and / or pharmaceutical formulations . this process achieves high degree of concentration in a closed system and at high flux with minimal trans - membrane pressure drop .