title: Effect of ceramic membrane channel diameter on limiting retentate protein concentration during skim milk microfiltration.
abstract: Our objective was to determine the effect of retentate flow channel diameter (4 or 6mm) of nongraded permeability 100-nm pore size ceramic membranes operated in nonuniform transmembrane pressure mode on the limiting retentate protein concentration (LRPC) while microfiltering (MF) skim milk at a temperature of 50°C, a flux of 55 kg · m(-2) · h(-1), and an average cross-flow velocity of 7 m · s(-1). At the above conditions, the retentate true protein concentration was incrementally increased from 7 to 11.5%. When temperature, flux, and average cross-flow velocity were controlled, ceramic membrane retentate flow channel diameter did not affect the LRPC. This indicates that LRPC is not a function of the Reynolds number. Computational fluid dynamics data, which indicated that both membranes had similar radial velocity profiles within their retentate flow channels, supported this finding. Membranes with 6-mm flow channels can be operated at a lower pressure decrease from membrane inlet to membrane outlet (ΔP) or at a higher cross-flow velocity, depending on which is controlled, than membranes with 4-mm flow channels. This implies that 6-mm membranes could achieve a higher LRPC than 4-mm membranes at the same ΔP due to an increase in cross-flow velocity. In theory, the higher LRPC of the 6-mm membranes could facilitate 95% serum protein removal in 2 MF stages with diafiltration between stages if no serum protein were rejected by the membrane. At the same flux, retentate protein concentration, and average cross-flow velocity, 4-mm membranes require 21% more energy to remove a given amount of permeate than 6-mm membranes, despite the lower surface area of the 6-mm membranes. Equations to predict skim milk MF retentate viscosity as a function of protein concentration and temperature are provided. Retentate viscosity, retentate recirculation pump frequency required to maintain a given cross-flow velocity at a given retentate viscosity, and retentate protein determination by mid-infrared spectrophotometry were all useful tools for monitoring the retentate protein concentration to ensure a sustainable MF process. Using 6-mm membranes instead of 4-mm membranes would be advantageous for processors who wish to reduce energy costs or maximize the protein concentration of a MF retentate.
authors.affiliation: Northeast Dairy Foods Research Center, Department of Food Science, Cornell University, Ithaca, NY 14853.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Adams
authors.affiliation: Northeast Dairy Foods Research Center, Department of Food Science, Cornell University, Ithaca, NY 14853. Electronic address: dmb37@cornell.edu.
authors.forename: David M
authors.initials: DM
authors.lastname: Barbano
mesh_terms: D000818:Animals; D001798:Blood Proteins / Q000032:analysis; D002516:Ceramics / Q000737:chemistry*; D003198:Computer Simulation; D005374:Filtration; D005511:Food Handling; D057446:Hydrodynamics; D008567:Membranes, Artificial; D008892:Milk / Q000737:chemistry*; D008894:Milk Proteins / Q000032:analysis; D010865:Pilot Projects; D014783:Viscosity
chemical_list: D001798:Blood Proteins; D008567:Membranes, Artificial; D008894:Milk Proteins
keywords: ceramic membranes; channel diameter; microfiltration; protein