Casein micelles separation from skimmed milk using a VSEP dynamic filtration module

A vibratory shear-enhanced filtration system (VSEP) was used for the separation of casein micelles from whey proteins of skim milk reconstituted from low heat milk powder, which has a similar protein content as fresh milk. This paper compares the performances of microfiltration (MF) with a 0.1 µm pore Teflon membrane and of an ultrafiltration (UF) polyethersulfone-one with 150 kD cut-off. The critical flux for stable operation was investigated in MF by increasing the permeate flux in steps while monitoring the transmembrane pressure. It was found to be 50 l h–1m–2 at a volume reduction ratio of 2 and the maximum frequency of 60.75 Hz (τw = 34 Pa). The UF membrane minimizes casein loss in the permeate (turbidity below 20 NTU) with a little reduction in permeate flux. Whey protein transmission in UF was found to be 65–70% for α-lactalbumin and 25–30% for β-lactoglobulin.

Fig. 5. Variation of permeate flux and turbidity with VRR in UF at maximum frequency. For casein micelles separation from whey proteins with the VSEP, the use of a UF membrane (with 150 kD cutoff) permits to minimize micelle loss while adequately transmitting acceptable whey proteins. Future tests will be carried out with 300 and 500 kD membranes to improve transmission of α-LA and β-LG and fluxes. At a VRR of 2, the critical fluxes for stable operation are in the range of 45 lh–1m–2 (UF) to 55 lh–1m–2 (MF) at a mean shear stress of 55 Pa, which compares favorably with cross flow filtration in tubular ceramic membranes [6].