Preparation of milk protein concentrates by ultrafiltration and continuous diafiltration: Effect of process design on overall efficiency

Abstract

High-milk-protein concentrates (>80% on a dry weight basis) are typically produced by ultrafiltration (UF) with constant-volume diafiltration (DF). To maximize protein retention at a commercial scale, polymeric spiral-wound UF membranes with a molecular weight cut-off (MWCO) of 10 kDa are commonly used. Flux decline and membrane fouling during UF have been studied extensively and the selection of an optimal UF-DF sequence is expected to have a considerable effect on both the process efficiency and the volumes of by-products generated. The objective of this study was to characterize the performance of the UF-DF process by evaluating permeate flux decline, fouling resistance, energy and water consumption, and retentate composition as a function of MWCO (10 and 50 kDa) and UF-DF sequence [3.5×-2 diavolumes (DV) and 5×-0.8DV]. The UF-DF experiments were performed on pasteurized skim milk using a pilot-scale filtration system operated at 50°C under a constant transmembrane pressure of 465 kPa. The results showed that MWCO had no effect on permeate flux for the same UF-DF sequence. Irreversible resistance was also similar for both sequences, whatever the MWCO, suggesting that soluble protein deposition within the pores is similar for all conditions. Despite lower permeate fluxes and greater reversible resistance for the 5×-0.8DV sequence, the overall energy consumption of the 2 UF-DF sequences was similar. However, the 3.5×-2DV sequence required more water for DF and generated larger volumes of permeate to be processed, which will require more membrane area and lead to greater environmental impact. A comparative life cycle assessment should however be performed to confirm which sequence has the lowest environmental impact.

Integrating Pressure-Driven Membrane Separation Processes to Improve Eco-Efficiency in Cheese Manufacture: A Preliminary Case Study

“…Compared to UF (10 kDa), protein transmission into permeate was greater in MF (0.1 µm). For MF, the global rejection coefficients were 0.99 and 0.95 for CN and serum proteins, respectively, whereas they were 1.00 and 0.99 for UF [ 12 , 19 ].…”

“…Finally, recirculation of a portion of the retentate in each stage directly impacts the tangential flow velocity, and indirectly affects the flow rate of the feed pump, and thus the TMP of each stage. Yet, in this study’s modeling method, the datasets were generated at a fixed TMP and with an unknown tangential flow velocity—moreover, the filtration unit used by Gavazzi-April et al [ 19 ] was not fitted with a recirculation loop. It is therefore possible that the results from the simulations of the membrane separation processes were not totally realistic.…”

“…All SM generated at the skimming stage was sent to the membrane separation processes for concentration and diafiltration (DF). The membrane separation processes described in Gavazzi-April et al [ 19 ] was used for scenario A, and the membrane separation processes described in Mercier-Bouchard et al [ 12 ] was used for scenario B. In scenario A, SM was concentrated to a volume concentration factor (VCF) of 3.5 then continuous DF with 2.0 diavolumes (DV) was performed—the diavolume is the ratio of the volume of consumed diluent to the volume of treated retentate [ 20 ].…”

“…This method uses filtration flux datasets to dimension a filtration unit to the desired productivity. Filtration datasets were obtained from Gavazzi-April et al [ 19 ] and Mercier-Bouchard et al [ 12 ] (UF and MF, respectively—experiments carried out at the pilot scale in the batch mode). These data showed the evolution of the permeation flux ( J ) as a function of the VCF.…”

Production of Liquid Milk Protein Concentrate with Antioxidant Capacity, Angiotensin Converting Enzyme Inhibitory Activity, Antibacterial Activity, and Hypoallergenic Property by Membrane Filtration and Enzymatic Modification of Proteins

“…Membrane technology is used for preparing concentrated milk proteins, fractionation of dairy proteins, demineralization of whey, and removal of microbial count in milk [9][10][11]. In some cases, ultrafiltration or nanofiltration operated with diafiltration mode was adopted to achieve high protein concentrate and avoid membrane fouling [12][13][14]. Some limitations in this context are reported.…”