Publications (2)2.56 Total impact
Article: Effect of membrane length, membrane resistance, and filtration conditions on the fractionation of milk proteins by microfiltration.[show abstract] [hide abstract]
ABSTRACT: We investigated the fractionation of casein micelles and the whey protein β-lactoglobulin (β-LG) of skim milk by crossflow microfiltration (0.1 μm) for the first time by a novel approach as a function of membrane length and membrane resistance. A special module was constructed with 4 sections and used to assess the effects of membrane length by measuring flux and β-LG permeation (or transmission) as a function of transmembrane pressure and membrane length. Depending on the position, the membranes were partly controlled by a deposit layer. A maximum for β-LG mass flow through the various membrane sections was found, depending on the position along the membrane. To study the effect of convective flow toward the membrane, membranes with 4 different intrinsic permeation resistances were assessed in terms of the permeation and fouling effects along the flow channel. From these findings, we derived a ratio between transmembrane pressure and membrane resistance, which was useful in reducing the effect of deposit formation and, thus, to optimize the protein permeation. In addition, the fouling effect was investigated in terms of reversible and irreversible fouling and, in addition, by differentiation between pressure-induced fouling and adsorption-induced (pressure-independent) fouling, again as a function of membrane length.Journal of Dairy Science 04/2012; 95(4):1590-602. · 2.56 Impact Factor
Article: Length dependency of flux and protein permeation in crossflow microfiltration of skimmed milk[show abstract] [hide abstract]
ABSTRACT: Crossflow microfiltration of skimmed milk to fractionate casein micelles and whey protein was investigated regarding length dependency of flux and whey protein permeation using a 1.2m long, 0.1μm tubular ceramic membrane. A special module consisting of four sections was constructed allowing to assess the effects of membrane length online by measuring flux and permeation of the whey protein β-lactoglobulin as a function of local processing conditions. It was found that under the applied filtration parameters (mean transmembrane pressure ΔpTM,m=0.5bar; temperature ϑ=55°C; wall shear stress τw=115Pa) main parts of the membrane were controlled by a deposit layer. In consequence, the transmission of the whey protein β-lactoglobulin increases from 38% to 87% from membrane inlet to membrane outlet. Results show that a local optimum for protein fractionation exists regarding membrane resistance and process conditions.Journal of Membrane Science - J MEMBRANE SCI. 01/2008; 325(2):887-894.
Article: Impact of colloidal interactions on the flux in cross-flow microfiltration of milk at different pH values: A surface energy approach[show abstract] [hide abstract]
ABSTRACT: The effect of colloidal interactions between casein micelles on the flux of a tubular ceramic membrane at cross-flow microfiltration (MF) of skim milk was studied. Filtration experiments were performed at a pH range of 6.8–5.9. Compared to filtration of milk at its native pH (6.8), the flux was reduced and membrane fouling proceeded faster when acidified milk was filtered. To explain the observed flux behavior, a new interaction model for casein micelles was developed, which incorporates on the basis of the extended DLVO (xDLVO) theory hydrophilic and hydrophobic interactions in the form of Lewis acid–base forces, which were derived from protein surface energies. It could be shown that deposit layer build-up is strongly influenced by the charge-dependent protein surface hydrophilicity, whereas electrostatic interactions between proteins can be neglected in high ionic strength fluids like milk.Journal of Membrane Science.