Impact of hollow fiber membrane length on the milk protein fractionation

Hollow fiber membranes, HFM, have not been established in milk protein fractionation by microfiltration. HFM of different lengths (0.3–1.2 m) were produced to vary the pressure drop along the module and thus to study the length dependent spatial distribution of flux and whey protein transmission along the flow path as a function of transmembrane pressure, Δp_TM, and feed volume flow rate. The objective was to identify the maximally possible module length for various combinations of Δp_TM and flow velocity leading to a pressure close to zero at the module outlet, thus avoiding negative Δp_TM and reverse permeate flow at the module end. A mean Δp_TM of 0.5 bar was identified as optimal for all module lengths to avoid deposit formation above the membrane-controlled limit, reaching a flux of 61.5 L m⁻² h⁻¹. An optimal HFM length of 0.6 m was identified for milk protein fractionation to obtain the highest flux and whey protein transmission. The shorter the module system, the higher is the possible volume flow rate to prevent excessive deposit formation and thus to achieve the best possible fractionation result.