Impact of feed concentration on milk protein fractionation by hollow fiber microfiltration membranes in diafiltration mode

Abstract

• HFM are effective alternatives with superior performance over SWM and CTM. • Optimization of preconcentration of casein fraction before starting diafiltration. • Optimal transmembrane pressure at 0.5 bar regarding mass flow. • Optimal concentration factor at 2.5 regarding specific filtration effort. • Permeate protein concentration and flux were limiting factors at lower or higher CF. Microfiltration (0.1 µm) in the diafiltration mode is performed using hollow fiber membranes (HFM) to separate the casein micelles and whey proteins in skim milk at 10 °C. This method of using HFM has not been widely applied in dairy technology. HFM differ from more established module systems such as ceramic tubular membranes (CTM) and spiral-wound membranes (SWM) in their geometry, flow conditions, and propensity to deposit formation. The objective of this study is to investigate the efficiency of fractionation according to the pre-concentration before starting diafiltration when using ultrafiltration permeate as diafiltration medium for transferring the whey proteins into the permeate. The concentration having constant pressure drop is compared with that having constant feed volume flow. The optimal process conditions are determined based on the following criteria: flux, whey protein transmission, whey protein mass flow, and time required for one volume turnover, i.e., diafiltration step. The process is found to be optimum at a transmembrane pressure of 0.5 bar, constant pressure drop of 1.0 bar m −1 , and concentration factor (CF) of 2.5. At a CF of 3, 80% whey protein depletion was achieved after 2.5 diafiltration steps. Therefore, HFM are confirmed as effective alternatives to SWM and CTM and are optimized in terms of pre-concentration of the casein fraction before starting diafiltration.