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Fouling and cleaning in food processing
Journal of Membrane hence, 53 (1990) 299-304 Elsevler Science Pubhshers B V , Amsterdam
299
Book Reviews
Foultng and Cleanrng m Food Processzng, Papers presented at the Third International Conference on Fouling and Cleaning held at Prien, Germany, June 5-7,1989, H.G. Kessler and D.B. Lund (Eds. ), pp. 331. This book contains twenty rune papers presented at the Third International Conference on Fouling and Cleaning m Food Processmg, held in Germany in 1989 Although only twelve of the papers deal directly with membranes there is much to be learned from the other studies. If you are interested m the ublqultous fouling problem, particularly with proteins, this book provides useful reading. Turning first to the membrane-related papers, three of these deal with surface treatment to mitigate fouling. Successful techmques described include coating with Langmuir-Blodgett layers of fluorinated compounds (Speaker et al ), sulphonation of Nuclepore membranes to increase protein transmission and carbon depositon to reduce hydrogen bonding effects (Chmiel and McDonogh), and use of non-ionic polymers such as Dextrans (Slvik et al ) The latter paper proposes a simple test procedure for assessing likely protein-coating interactions. Although none of the surface treatments provide a complete solution to the foulmg problem, they confirm the view that this ISa worthwhile approach with potential benefits. Another four of the membrane papers describe ways of enhancing flux and, m some cases, alleviating fouhng. Pulsed and baffled flow, which is recelvmg increasing attention, is described by Finnigan and Howell, and Chmiel and McDonogh. Flux enhancements up to 2 x are reported for protem UF. This is a significant improvement provided it can be achieved without a large capital cost penalty. The use of electro-UF for gelatine is described by Almar et al This technique is also in vogue and the paper confirms the potential for improvement. As for pulsing flow, the efficacy of electro-UF will have to be balanced against the practicality of the techmque. Plett describes the patented Bactocatch process of Alfa Laval, used to remove bacteria from milk The most interesting aspect of the work is that the ceramic membranes used are operated so that the transmembrane pressure (TMP) is constant over the entire tube length. This is achieved by cocurrent circulation of the filtrate which avoids a high TMP at the tube mlet As a result fouling is much more effectively controlled along the tube. The cleaning of tubular RO and UF membranes after exposure to skim milk is presented by Kulozik and Kessler. They show that the most important parameters are AP and shear stress at the surface. In addition, the presence of &valent cations such as calcmm can mcrease the power of adhesion of proteins Two papers on analytical techniques provide mslght into the fouhng process 0376-7388 /90/$03
50
0 1990 -
Elsewer Science Pubhshers B V
300
Daufin and co-workers use I.R. spectroscopy and X-ray photoelectron spectroscopy to examine whey protein deposits and phosphate-protein interactions on the surface and within the pores. Wahlgren and Arnebrant describe the use of ellipsometry for m-situ examination of protein adsorption, and observe that fatty-acid-free BSA adsorbs more than does “native” BSA. Two membrane papers, not relating to fouling are of interest. Hubble describes a model for protein transmission through microfiltration membranes, showing that at an optimal pressure the transmission (mass flow rate) could be at a maximum. The other paper describes membrane filtration of supercritical CO, (there seems to be no limit to membrane applications). Several of the non-membrane papers will be of interest to membrane practitioners. For example, Gotham et al. explain the sigmficance of protein aggregate formation as a precursor to fouhng of heat exchangers; this may have parallels with membrane process fouling. Again calcmm is shown to exacerbate the problem. Bradley et al. report that oscillatory flow enhances heat transfer and reduces fouling with whey protein concentrates. Sandu reports that the fouling layer on heated surfaces is anisotropic with a compact sublayer and a spongy deposit with an upper surface influenced by crossflow. This ISvery similar to deposits of BSA on UF membranes observed m the reviewer’s laboratory. Other parallels mclude the significance of surface smoothness mentioned by Yoon and Lund. Pseudomonas fhorescens blofilm fouling ISaffected by fluid velocity and nutrient level. Indeed, the fouling resistance drops if the nutrient level is reduced, and this agrees with our own experience with biofilms on UF membranes. Finally, the paper by Paulsson and Tragardh is relevant to studies of microfiltration (MF) . They describe the removal of fine particles from a surface as a function of surface shear, observing that a critical shear stress is necessary for any removal and that above the critical value the removal becomes proportional to (crossflow )’ ‘. Those who are analyzing MF will see the relevance of this work. In summary, I found this book interesting and enlightening. However, I believe the editors missed an opportunity by not including the discussion sessions I would have expected a lively m&change amongst the various disciplmes present at the meetmg Perhaps that pomt can be considered by Dr. T. Yano (University of Tokyo, Agricultural Technology) who is organizing the next conference m 1993. The book IS in soft cover and inexpensive (US$35 or DM 70). It can be obtained from Dr. Daryl Lund (Department of Food Science, P 0. Box 231, Rutgers University, New Brunswick, NJ 08903, U.S A ) or Dr. Heinz Kessler (Institute for Dauy Science and Food Processing, Techn Umversity, Munich, D-8050 Frelsing, Weihenstephan, Germany). AG FANE Centre for Membrane and Separation Technology Unlverslty of New South Wales Kensvzgton, Australra
299
Book Reviews
Foultng and Cleanrng m Food Processzng, Papers presented at the Third International Conference on Fouling and Cleaning held at Prien, Germany, June 5-7,1989, H.G. Kessler and D.B. Lund (Eds. ), pp. 331. This book contains twenty rune papers presented at the Third International Conference on Fouling and Cleaning m Food Processmg, held in Germany in 1989 Although only twelve of the papers deal directly with membranes there is much to be learned from the other studies. If you are interested m the ublqultous fouling problem, particularly with proteins, this book provides useful reading. Turning first to the membrane-related papers, three of these deal with surface treatment to mitigate fouling. Successful techmques described include coating with Langmuir-Blodgett layers of fluorinated compounds (Speaker et al ), sulphonation of Nuclepore membranes to increase protein transmission and carbon depositon to reduce hydrogen bonding effects (Chmiel and McDonogh), and use of non-ionic polymers such as Dextrans (Slvik et al ) The latter paper proposes a simple test procedure for assessing likely protein-coating interactions. Although none of the surface treatments provide a complete solution to the foulmg problem, they confirm the view that this ISa worthwhile approach with potential benefits. Another four of the membrane papers describe ways of enhancing flux and, m some cases, alleviating fouhng. Pulsed and baffled flow, which is recelvmg increasing attention, is described by Finnigan and Howell, and Chmiel and McDonogh. Flux enhancements up to 2 x are reported for protem UF. This is a significant improvement provided it can be achieved without a large capital cost penalty. The use of electro-UF for gelatine is described by Almar et al This technique is also in vogue and the paper confirms the potential for improvement. As for pulsing flow, the efficacy of electro-UF will have to be balanced against the practicality of the techmque. Plett describes the patented Bactocatch process of Alfa Laval, used to remove bacteria from milk The most interesting aspect of the work is that the ceramic membranes used are operated so that the transmembrane pressure (TMP) is constant over the entire tube length. This is achieved by cocurrent circulation of the filtrate which avoids a high TMP at the tube mlet As a result fouling is much more effectively controlled along the tube. The cleaning of tubular RO and UF membranes after exposure to skim milk is presented by Kulozik and Kessler. They show that the most important parameters are AP and shear stress at the surface. In addition, the presence of &valent cations such as calcmm can mcrease the power of adhesion of proteins Two papers on analytical techniques provide mslght into the fouhng process 0376-7388 /90/$03
50
0 1990 -
Elsewer Science Pubhshers B V
300
Daufin and co-workers use I.R. spectroscopy and X-ray photoelectron spectroscopy to examine whey protein deposits and phosphate-protein interactions on the surface and within the pores. Wahlgren and Arnebrant describe the use of ellipsometry for m-situ examination of protein adsorption, and observe that fatty-acid-free BSA adsorbs more than does “native” BSA. Two membrane papers, not relating to fouling are of interest. Hubble describes a model for protein transmission through microfiltration membranes, showing that at an optimal pressure the transmission (mass flow rate) could be at a maximum. The other paper describes membrane filtration of supercritical CO, (there seems to be no limit to membrane applications). Several of the non-membrane papers will be of interest to membrane practitioners. For example, Gotham et al. explain the sigmficance of protein aggregate formation as a precursor to fouhng of heat exchangers; this may have parallels with membrane process fouling. Again calcmm is shown to exacerbate the problem. Bradley et al. report that oscillatory flow enhances heat transfer and reduces fouling with whey protein concentrates. Sandu reports that the fouling layer on heated surfaces is anisotropic with a compact sublayer and a spongy deposit with an upper surface influenced by crossflow. This ISvery similar to deposits of BSA on UF membranes observed m the reviewer’s laboratory. Other parallels mclude the significance of surface smoothness mentioned by Yoon and Lund. Pseudomonas fhorescens blofilm fouling ISaffected by fluid velocity and nutrient level. Indeed, the fouling resistance drops if the nutrient level is reduced, and this agrees with our own experience with biofilms on UF membranes. Finally, the paper by Paulsson and Tragardh is relevant to studies of microfiltration (MF) . They describe the removal of fine particles from a surface as a function of surface shear, observing that a critical shear stress is necessary for any removal and that above the critical value the removal becomes proportional to (crossflow )’ ‘. Those who are analyzing MF will see the relevance of this work. In summary, I found this book interesting and enlightening. However, I believe the editors missed an opportunity by not including the discussion sessions I would have expected a lively m&change amongst the various disciplmes present at the meetmg Perhaps that pomt can be considered by Dr. T. Yano (University of Tokyo, Agricultural Technology) who is organizing the next conference m 1993. The book IS in soft cover and inexpensive (US$35 or DM 70). It can be obtained from Dr. Daryl Lund (Department of Food Science, P 0. Box 231, Rutgers University, New Brunswick, NJ 08903, U.S A ) or Dr. Heinz Kessler (Institute for Dauy Science and Food Processing, Techn Umversity, Munich, D-8050 Frelsing, Weihenstephan, Germany). AG FANE Centre for Membrane and Separation Technology Unlverslty of New South Wales Kensvzgton, Australra