Effect of membrane length, membrane resistance, and filtration conditions on the fractionation of milk proteins by microfiltration

Technische Universität München, Weihenstephaner Berg 1, 85354 Freising-Weihenstephan, Germany.
Journal of Dairy Science (Impact Factor: 2.57). 04/2012; 95(4):1590-602. DOI: 10.3168/jds.2011-4292
Source: PubMed


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.

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    • "Microfiltration (MF) has been widely used for fractionation, protein concentration and bacterial load reduction of milk (Daufin et al., 2001; Lawrence, Kentish, O'Connor, Barber, & Stevens, 2008; Piry et al., 2012; Tomasula et al., 2011). In addition, it has been shown that changing pH or ionic strength by adding minerals to skimmed milk or casein dispersions can modify conformation of casein micelles and affect membraneeprotein interactions leading to flux reduction (Bouzid et al., 2008; Jimenez-Lopez et al., 2008, 2011; Kühnl et al., 2010; Rabiller-Baudry, Gesan-Guiziou, Roldan- Calbo, Beaulieu, & Michel, 2005) Flux decrease on UF of skimmed milk has been generally associated to the protein fraction formed mainly by casein micelles (Le Berre & Daufin, 1998) Caseins are the most important proteins in milk (~28 g/L À1 ) and constitute about the 80% of the total protein fraction of milk. "
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    ABSTRACT: The flux behavior of 0.8 and 0.5 mu m silicon nitride microsieves was studied in the pH range from 6 to 9 during microfiltration of milk protein dispersions supplemented with a mineral complex. The physicochemical properties of these dispersions were assessed by particle size distribution (PSD), zeta potential and rheological measurements. Microfiltration was carried out in a pilot cross-flow system where back pulsing was used. Results showed that increasing protein concentration from 30 to 90 g L-1 at pH approximate to 7 has a negligible effect on charge and PSD but increased viscosity and strongly reduced performance of both 0.5 and 0.8 gm microsieves. Adding minerals reduced further the 0.8 gm membrane flux and avoid filtration through the 0.5 mu m membrane, despite the fact that PSD was approximate to 0.3 mu m in all solutions. Raising the pH of dispersions at 9.0, which is higher than the isoelectric pH of both micelles and microsieves, drastically increased permeate flux of both membranes. Results from this work point out that even under quite high ionic strength conditions, the flux behavior of microsieves is mainly controlled by repulsive electrostatic protein-membrane interactions, hence, the pH of the dispersion and the membrane charge are critical when processing complex dairy products.
    Lebensmittel-Wissenschaft und-Technologie 12/2014; 59(2):827-833. DOI:10.1016/j.lwt.2014.06.057 · 2.42 Impact Factor
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    • "Gas bubbling [10] [11] [12] [13] or scouring particles [14] are also proposed to reduce fouling. It is also reported that pressure loss along the membrane is responsible for the greater fouling in nonuniform crossflow processes, so uniform transmembrane pressure crossflow filtration system has been proposed to reduce fouling and cake build-up [15] [16] [17]. Though effective, these various strategies present drawbacks as well for skim milk filtration [18]. "
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    ABSTRACT: This study investigates effects of ultrasound (US) on cross-flow ultrafiltration of skim milk by multi-scale characterization, using a custom designed “SAXS Cross-Flow US-coupled Filtration Cell”. The study of flow properties of casein micelle suspensions shows an evolution of their rheological behavior from Newtonian to shear-thinning until the emergence of yield stress with the increase of concentration (from 27 g L−1 to 216 g L−1). The concentration profiles during cross-flow filtration of skim milk have been revealed for the first time by real-time in-situ Small Angle X-ray Scattering (SAXS) measurement. Without any change of internal structure of casein micelles and membrane selectivity, the applied ultrasound (20 kHz, 2 W cm−2) leads to a significant increase of permeate flux arising from a disruption of concentrated layer. Varying the US intensity from 0.6 W cm−2 to 2.9 W cm−2 does not affect the US enhancement factor, which however depends on the feed concentration. In fact, increase of feed concentration induces the formation of highly cohesive fouling layer during filtration that the applied US could hardly disrupt. Results also suggest that the preventive US application mode is promising since formation of the reversible fouling layer was strongly limited in this mode.
    Journal of Membrane Science 11/2014; 470:205–218. DOI:10.1016/j.memsci.2014.07.043 · 5.06 Impact Factor
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    • "Typically, linear scale-up is accomplished by keeping the length of the module from feed stream inlet to retentate stream exit the same [27]. However, industrial scale systems for whey protein concentration incorporate long (96.5 cm) spiral wound membranes, often placed four in a row (386 cm long in total), where length dependent variations come into play [18] [21]. Proceeding down the length of the module both J v and Q R decrease somewhat, making β somewhat higher at the inlet and lower at the exit. "
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    ABSTRACT: This work examines the use of wide-pore negatively charged ultrafiltration membranes for whey protein concentration. The hypothesis is that by placing a negative charge on the surface of an ultrafiltration membrane, negatively charged proteins are rejected by electrostatic repulsion and not simply sized based sieving. This allows using wide-pore membranes that have a higher flux without suffering a loss in protein recovery. It was found that negatively charged 100 kDa ultrafiltration membranes had the same protein recovery as 10 kDa unmodified membranes used in the dairy industry, but offered a flux that was at least two-fold higher. The new membranes were used for a 40-fold concentration of whey with subsequent diafiltration to mimic the industrial process for making whey protein concentrate. Mass balance models of concentration and diafiltration were developed and each agreed well with the experimental results. The experimental methods and mathematical models developed in this work can be used to design, simulate and optimize different process flow sheets, and explore the effect of various operating conditions on the membrane processing of whey.
    Journal of Membrane Science 10/2014; 475. DOI:10.1016/j.memsci.2014.10.049 · 5.06 Impact Factor
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