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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Available from: Antti Heino, Jan 28, 2016
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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.
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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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    • "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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