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Microfiltration of skim milk for casein concentrate manufacture
Desalination 200 (2006) 305–306
Microfiltration of skim milk for casein concentrate manufacture Nicole Lawrencea, Sandra Kentisha*, Andrea O’Connora, Geoff Stevensa, Andrew Barberb a
Department of Chemical and Biomolecular Engineering, The University of Melbourne, Victoria 3010, Australia email: [email protected] b Burra Foods, P.O. Box 379, Korumburra, Victoria, 3950, Australia Received 26 October 2005; accepted 2 March 2006
1. Introduction
2. Theory and experimental
The separation of casein from serum proteins using membrane technology is becoming a popular process in the dairy industry. This process can provide a casein concentrate stream and a whey protein stream in a natural state for further processing. However, the microfiltration (MF) of skim milk can result in high levels of fouling and thus processing parameters need to be optimised if production is to be successful. These processing parameters also affect the extent of the separation of the proteins. Classically this operation has been conducted using ceramic membranes [1,2] with restrictions often placed in the permeate channel path in order to maintain a constant transmembrane pressure (TMP) along the membrane length [3]. However, more recent work [4] has shown that the use of polymeric spiral wound membranes may also be viable in this application. It was the intent of the present work to confirm this viability.
Initial experiments were conducted on site at Burra Foods, Australia, using a small pilot plant that incorporated a single full-size spiral wound membrane element. Later experiments utilised a laboratory scale Osmonics flat sheet membrane system. Two different PTI (Domnick Hunter, PTI Advanced Filtration, USA) polymeric microfiltration membranes of 0.3 µm and 0.5 µm pore size were used. In all cases, skim milk taken directly from the milk separator was used. Constant concentration runs were conducted in order to model the fouling mechanisms. In these experiments, constant concentration was maintained by continuously recirculating the retentate back to the feed tank, and recirculating permeate periodically. Concentrating runs were also completed to determine the maximum total solids and protein levels that could be achieved in the spiral wound set-up. Different temperatures, pressures, crossflow velocities and the two different pore size membranes were analysed. Crossflow velocity could only be investigated in the flat sheet experiments. Permeate flux was monitored throughout the
*Corresponding author.
Presented at EUROMEMBRANE 2006, 24–28 September 2006, Giardini Naxos, Italy. 0011-9164/06/$– See front matter © 2006 Published by Elsevier B.V. doi:10.1016/j.desal.2006.03.328
306
N. Lawrence et al. / Desalination 200 (2006) 305–306
runs, and water flux measurements were taken before and after each processing run. Skim milk feed samples were analysed for fat, protein and total solids. Permeate samples were taken at regular intervals to determine the transmission levels of casein into the permeate. HPLC analysis was completed on both retentate and permeate to determine the rejection rate of both casein and whey proteins. 3. Results and discussion The permeate was visibly clear in all runs suggesting very effective separation of caseins from whey proteins. During constant concentration runs, the production flux rates were highly stable over a 2-h period within each set of conditions. Crossflow velocities and temperature had a larger effect on the steady state flux than the transmembrane pressure or membrane pore size. Concentrating runs show a continuous decline of permeate flux over time (Fig. 1). The
transmembrane pressure was maintained over this processing period. Upon the introduction of diafiltration water (DF), the flux immediately rose, and then again declined with time upon further concentration of the protein and total solids. 4. Conclusions Whilst numerous authors have previously shown the use of ceramic membranes for this separation, polymeric membranes seem to be effective even without the use of sophisticated techniques to control TMP. Based on our limited results to date, there is no evidence of membrane fouling causing major disruption to production. However, further assessment at higher total solids concentration is required to confirm fouling effects. Results show the effect of temperature, pressure and velocity on fouling behaviour, and hence on production flux and separation characteristics of the membrane system.
J (kg/m2 h)
References [1]
20 18 16 14 12 10 8 6 4 2 0
DF added
[2]
0
60 120 180 240 300 360 420 480 540 600 660 Time (min)
Fig. 1. Production flux (kg/m2 h) versus time for a concentrating run on the spiral wound membrane plant over a 10-h run (0.3 mm pore size, 1.5 bar transmembrane pressure, 10oC).
[3]
[4]
O. Le Berre and G. Daufin, Skimmilk crossflow microfiltration performance versus permeation flux to wall shear stress ratio, J. Membr. Sci., 117 (1996) 261–270. M. Mercier-Bonin, C. Fonade and G. GésanGuiziou, Application of gas/liquid two-phase flows during crossflow microfiltration of skimmed milk under constant flux conditions, Chem. Eng. Sci., 59 (2004) 2333–2341. L.V. Saboya and J.-L. Maubois, Current developments of microfiltration technology in the dairy industry, Lait, 80 (2000) 541–553. Domnick Hunter (2005), http://www.domnickhunter-af.com/index.cfm?fuseaction=Products. main, accessed 21/11/05.
Microfiltration of skim milk for casein concentrate manufacture Nicole Lawrencea, Sandra Kentisha*, Andrea O’Connora, Geoff Stevensa, Andrew Barberb a
Department of Chemical and Biomolecular Engineering, The University of Melbourne, Victoria 3010, Australia email: [email protected] b Burra Foods, P.O. Box 379, Korumburra, Victoria, 3950, Australia Received 26 October 2005; accepted 2 March 2006
1. Introduction
2. Theory and experimental
The separation of casein from serum proteins using membrane technology is becoming a popular process in the dairy industry. This process can provide a casein concentrate stream and a whey protein stream in a natural state for further processing. However, the microfiltration (MF) of skim milk can result in high levels of fouling and thus processing parameters need to be optimised if production is to be successful. These processing parameters also affect the extent of the separation of the proteins. Classically this operation has been conducted using ceramic membranes [1,2] with restrictions often placed in the permeate channel path in order to maintain a constant transmembrane pressure (TMP) along the membrane length [3]. However, more recent work [4] has shown that the use of polymeric spiral wound membranes may also be viable in this application. It was the intent of the present work to confirm this viability.
Initial experiments were conducted on site at Burra Foods, Australia, using a small pilot plant that incorporated a single full-size spiral wound membrane element. Later experiments utilised a laboratory scale Osmonics flat sheet membrane system. Two different PTI (Domnick Hunter, PTI Advanced Filtration, USA) polymeric microfiltration membranes of 0.3 µm and 0.5 µm pore size were used. In all cases, skim milk taken directly from the milk separator was used. Constant concentration runs were conducted in order to model the fouling mechanisms. In these experiments, constant concentration was maintained by continuously recirculating the retentate back to the feed tank, and recirculating permeate periodically. Concentrating runs were also completed to determine the maximum total solids and protein levels that could be achieved in the spiral wound set-up. Different temperatures, pressures, crossflow velocities and the two different pore size membranes were analysed. Crossflow velocity could only be investigated in the flat sheet experiments. Permeate flux was monitored throughout the
*Corresponding author.
Presented at EUROMEMBRANE 2006, 24–28 September 2006, Giardini Naxos, Italy. 0011-9164/06/$– See front matter © 2006 Published by Elsevier B.V. doi:10.1016/j.desal.2006.03.328
306
N. Lawrence et al. / Desalination 200 (2006) 305–306
runs, and water flux measurements were taken before and after each processing run. Skim milk feed samples were analysed for fat, protein and total solids. Permeate samples were taken at regular intervals to determine the transmission levels of casein into the permeate. HPLC analysis was completed on both retentate and permeate to determine the rejection rate of both casein and whey proteins. 3. Results and discussion The permeate was visibly clear in all runs suggesting very effective separation of caseins from whey proteins. During constant concentration runs, the production flux rates were highly stable over a 2-h period within each set of conditions. Crossflow velocities and temperature had a larger effect on the steady state flux than the transmembrane pressure or membrane pore size. Concentrating runs show a continuous decline of permeate flux over time (Fig. 1). The
transmembrane pressure was maintained over this processing period. Upon the introduction of diafiltration water (DF), the flux immediately rose, and then again declined with time upon further concentration of the protein and total solids. 4. Conclusions Whilst numerous authors have previously shown the use of ceramic membranes for this separation, polymeric membranes seem to be effective even without the use of sophisticated techniques to control TMP. Based on our limited results to date, there is no evidence of membrane fouling causing major disruption to production. However, further assessment at higher total solids concentration is required to confirm fouling effects. Results show the effect of temperature, pressure and velocity on fouling behaviour, and hence on production flux and separation characteristics of the membrane system.
J (kg/m2 h)
References [1]
20 18 16 14 12 10 8 6 4 2 0
DF added
[2]
0
60 120 180 240 300 360 420 480 540 600 660 Time (min)
Fig. 1. Production flux (kg/m2 h) versus time for a concentrating run on the spiral wound membrane plant over a 10-h run (0.3 mm pore size, 1.5 bar transmembrane pressure, 10oC).
[3]
[4]
O. Le Berre and G. Daufin, Skimmilk crossflow microfiltration performance versus permeation flux to wall shear stress ratio, J. Membr. Sci., 117 (1996) 261–270. M. Mercier-Bonin, C. Fonade and G. GésanGuiziou, Application of gas/liquid two-phase flows during crossflow microfiltration of skimmed milk under constant flux conditions, Chem. Eng. Sci., 59 (2004) 2333–2341. L.V. Saboya and J.-L. Maubois, Current developments of microfiltration technology in the dairy industry, Lait, 80 (2000) 541–553. Domnick Hunter (2005), http://www.domnickhunter-af.com/index.cfm?fuseaction=Products. main, accessed 21/11/05.