ECI Symposium Series, Volume RP2: Proceedings of 6th International Conference on Heat Exchanger Fouling and Cleaning -

Challenges and Opportunities, Editors Hans Mller-Steinhagen, M. Reza Malayeri, and A. Paul Watkinson, Engineering Conferences
International, Kloster Irsee, Germany, June 5 - 10, 2005

FOULING OF HEAT EXCHANGERS BY DAIRY FLUIDS A REVIEW

B. Bansal1* and X. D. Chen2

Department of Chemical and Materials Engineering

The University of Auckland, Auckland, New Zealand
1
b.bansal@auckland.ac.nz
2
d.chen@auckland.ac.nz

ABSTRACT required due to the concerns of product

Fouling of heat exchangers in the dairy industry has quality/contamination instead of performance of the heat
been investigated extensively and a large number of studies exchanger.
are reported in literature. This review focuses on the Milk is a complicated biological fluid and contains a
mechanisms of milk fouling, detailing the role of protein number of species. Its average composition in weight % is:
denaturation and aggregation reactions as well as mass water 87.5, total solids - 13.0, fat 3.9, lactose 4.8,
transfer. It has also been endeavoured to review the effect proteins 3.4 (casein 2.6, -lactoglobulin (-Lg) 0.32,
of a number of different factors on milk fouling. These -lactalbumin (-La) 0.12), minerals 0.8, and small
factors have been divided into five major categories: milk quantities of other miscellaneous species (Bylund 1995).
composition, operating conditions, heat exchanger Thermal response of these constituents generally differs
characteristics, presence of micro-organisms, and location from each other. -Lg has high heat sensitivity and figures
of fouling. prominently in the fouling process (Lyster 1970, Lalande et
al 1985, Gotham et al. 1992, Delplace et al. 1994, Bylund
1995). Milk fouling can be classified into two categories
INTRODUCTION (Burton 1968, Lund and Bixby 1975, Visser and Jeurnink
In the dairy industry, thermal processing is an energy 1997, Changani et al. 1997): i) Type A (protein) fouling
intensive process since every product is heated at least once takes place for temperatures between 75oC and 110oC. The
(de Jong 1997). Processing over 13 billion litres of milk deposits are white, soft, and spongy (milk film) and their
every year in New Zealand (Fonterra 2004) means the composition is 50-70% proteins (mainly -Lg), 30-40%
efficiency of the heating process is of paramount minerals, and 4-8% fat, ii) Type B (mineral) fouling takes
importance. Fouling of heat exchangers is a serious issue as place at temperatures above 110oC. The deposits are hard,
it reduces heat transfer efficiency and increases pressure compact, granular in structure, and grey in colour (milk
drop and hence affects the economy of processing plant stone) and their composition is 70-80% minerals (mainly
(Mller-steinhagen 1993, Toyoda et al. 1994). As a result calcium phosphate), 15-20% proteins, and 4-8% fat.
of fouling, there is a possibility of deterioration in product
quality since the process fluid cannot be heated up to the MECHANISMS OF MILK FOULING
required temperature (say for pasteurisation or sterilization). Whey proteins constitute just around 5% of the milk solids
The deposits dislodged by the flowing fluid can also cause but they account for more than 50% of the fouling deposits
contamination. in type A fouling. -Lg and -La are the two major whey
Fouling related costs are: additional energy, lost proteins in the milk. Both are of globular nature and heat
productivity, additional equipment, manpower, chemicals, sensitive, however, -Lg is the dominant protein in heat
environmental impact (Gillham et al. 2000). Generally milk induced fouling (Lyster 1970, Lalande et al 1985, Bylund
fouling is so rapid that heat exchangers need to be cleaned 1995). The caseins are resistant to thermal processing but
every day to maintain production capability and efficiency do precipitate upon acidification (Visser and Jeurnink
and meet strict hygiene standards. In comparison, the heat 1997). Although the exact mechanisms and reactions
exchangers in other major processing plants like petroleum, between different milk components are not yet fully
petrochemical etc need to be cleaned only once or twice a understood, a relationship between the denaturation of
year. According to Georgiadis et al. (1998), in the dairy
native -Lg and fouling of heat exchangers has been
industry the cost due to the interruption in production can
established (Dalgleish 1990). Upon heating of milk, the
be dominant compared with the cost due to reduction in
native proteins (-Lg) first denature (unfold) and expose the
performance efficiency. Along with the cost, quality issues
core containing reactive sulphydryl groups. The denatured
are equally important and in fact many times a shut down is
protein molecules then react with the similar or other types

*
Current address: Fonterra Co-operative Group Ltd, Private Bag 11029, Palmerston North, New Zealand
Email: bipan.bansal@fonterra.com

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150 Heat Exchanger Fouling and Cleaning - Challenges and Opportunities [2005], Vol. RP2, Article 23

of protein molecules like casein, -lactalbumin (-La) and down to 4 s and found that the first layer was made of
form aggregates. The rate of fouling may be different for proteinaceous material.
the denatured and aggregated proteins. Being larger in size, Fouling in a heat exchanger depends on bulk and
the transport of the aggregated proteins from the bulk to the surface processes. The deposition is a result of a number of
heat transfer surfaces may be more difficult compared with stages (Belmar-Beiny and Fryer 1993):
the denatured proteins (Treybal 1981, Chen 2000).
According to Changani et al. (1997), fouling occurs when i) denaturation and aggregation of proteins in the bulk
the aggregation takes place next to the heated surfaces. ii) transport of the aggregated proteins to the surface
Delplace et al. (1994) experimentally observed that only iii) surface reactions resulting in incorporation of protein
3.6% of denatured -Lg was involved in deposit formation. into the deposit layer and
Lalande et al. (1985) found the figure to be around 5%. iv) possible re-entrainment or removal of deposits.
However, it is not clear whether fouling was primarily
caused by the aggregated proteins or the denatured proteins The step controlling the overall fouling hence may
deposited first on the heat transfer surfaces and the either be related to physical/chemical changes in the
aggregation took place subsequently. Toyoda et al. (1994) proteins or the mass transfer of the proteins between the
modelled the milk fouling process based on the assumption fluid and the heat transfer surface. In some cases, it may be
that only aggregated proteins resulted in fouling. According a combination of both. Belmar-Beiny et al. (1993) and
to Delplace et al. (1997), fouling is controlled by the Schreier and Fryer (1995) proposed that fouling was
aggregation reaction of protein molecules. de Jong et al. dependent on the bulk and surface reactions and not on the
(1992) found that the formation of protein aggregates mass transfer. It was also proposed that the fouling rate was
reduces fouling. van Asselt et al. (2005) believe that -Lg independent of the concentration of foulant in the liquid
aggregates are not involved in fouling reactions. Chen et al. (Schreier and Fryer 1995).
(1998a, 2001) in their mathematical modelling considered According to Lalande et al. (1985), Hege and Kessler
that along with aggregated proteins, denatured proteins also (1986), Arnebrant et al. (1987), and Kessler and Beyer
took part in deposit formation. (1991), protein denaturation is the governing reaction. On
Usually an induction period is required for the the other hand, Lalande and Ren (1988) and Gotham et al.
formation of the protein aggregates or insoluble mineral (1992) have observed that protein aggregation is the
complexes before noticeable amount of deposits are formed governing reaction. de Jong et al. (1992) observed that the
(Elofsson et al. 1996, Visser and Jeurnink 1997, de Jong et deposition of milk constituents in heat exchangers is a
al. 1998). This time period varies between 1 and 60 reaction-controlled adsorption of denatured proteins.
minutes for tubular heat exchangers (de Jong 1997) but is Toyoda et al. (1994) suggested that mass transfer between
much shorter or even instantaneous in plate heat exchangers bulk fluid and thermal boundary layer was also important
where intense mixing of fluid takes place due to higher along with the bulk and surface reactions. Also only
turbulence (Belmar-Beiny et al. 1993). Activation energies aggregated proteins in the thermal boundary layer were able
of deposition reactions for both types of heat exchangers are to cause deposition. Changani et al. (1997), Anema and
reported to be similar, which suggests that the underlying McKenna (1996), and Chen et al. (1998a) suggested that the
processes are the same in both cases (Fryer and Belmar- protein unfolding or denaturation step is reversible whereas
Beiny 1991). Ruegg et al. (1977), Lalande et al. (1985), Arnebrant et al
The native proteins may adsorb on the heat transfer (1987), and Roefs and de Kruif (1994), and Karlsson et al.
surface at low temperatures i.e. below 70oC with coverage (1996) have found evidence that the denaturation step is
of less than 5 mg/m2 but this does not result in any fouling. irreversible. In comparison, the protein aggregation step
According to Fryer and Belmar-Beiny (1991), protein has been reported to be always irreversible (Mulvihill and
denaturation in heat exchangers starts only at temperatures Donovan 1987, Changani et al 1997, Anema and McKenna
above 70-74oC. They also reported that the first deposit 1996, and Chen et al 1998a).
layer (usually < 5m) is largely mineral. According to Chen et al. (2001) proposed, based on their
Visser and Jeurnink (1997) mainly the proteins form the experimental data, that fouling was caused by both
first layer. Analysis of deposits after fouling for an denatured and aggregated whey proteins and perhaps
extended period usually shows that the deposits near the primarily influenced by the presence of the denatured (but
surface contain a higher proportion of minerals. This is not the aggregated) proteins in the bulk. They also included
caused by the diffusion of minerals through the deposits to the mechanism of the reversible formulation in the protein
the surface rather than minerals forming firstly on the denaturation process. Their simulated results showed that
surface (Belmar-Beiny et al. 1993). Belmar-Beiny and similar accuracy of the fouling predictions was achieved
Fryer (1993) analysed deposits with contact heating times with different combinations of unfolded and aggregated

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Bansal and Chen: 151

proteins for hot surface cold fluid scenario. However, aggregation of proteins before the heating section, which
different mechanisms may lead to quite different predictions then leads to lower fouling in the heat exchangers (Bell and
for cold surface hot fluid scenario. This illustrates the Sanders 1944, Burton 1968, Mottar and Moermans 1988,
need to study the cold surface effect for better Foster et al. 1989).
understanding. Reconstituted milk gives much less fouling since
around 25% of -Lg is denatured during the production of
milk powders (Changani et al. 1997, Visser and Jeurnink
Factors Affecting Milk Fouling 1997). The concentration of calcium is reported to be 9%
Milk fouling may be unavoidable practically and less in the reconstituted milk, which would result in less
continuous efforts are required to minimise it. Fouling in a fouling (Changani et al. 1997). In contrast, Newstead et al.
heat exchanger depends on various parameters like heat (1998) found that UHT fouling rates of the recombined milk
transfer method, hydraulic and thermal conditions, heat increased with increasing preheat treatment (preheating
transfer surface characteristics, type and quality of milk temperature x preheating time). The fouling deposits also
along with its processing history etc. The factors affecting had high levels of fat (up to 60% or more) compared with
milk fouling in heat exchangers can be broadly classified the deposits formed during fresh milk processing (10% or
into five major categories: less). The difference is attributed to changes in fat-globule
membranes. Fung et al. (1998) studied the effect of damage
Milk composition to milk fat globule membrane by a cavitating pump on
Operating conditions in heat exchangers fouling of whole milk. The fouling rate was enhanced and
Type and characteristics of heat exchangers the argument was that the damage to the membranes results
Presence of micro-organisms in the fat globules to coalesce, which then tend to migrate
Location of fouling faster towards the heated wall.

Milk composition Operating conditions in heat exchangers

The composition of milk depends on its source and Important operating parameters that can be varied in a
hence may not be possible to change. A seasonal variation heat exchanger are: air content, velocity/turbulence, and
in milk fouling depends on differences in its composition temperature.
(Butron 1967, Belmar-Beiny et al. 1993, de Jong 1997). The presence of air in milk enhances fouling (Burton
Increasing the protein concentration results in higher 1968, de Jong 1997, de Jong et al. 1998). However, fouling
fouling (Toyoda et al. 1994, Changani et al. 1997). is enhanced only when air bubbles are formed on heat
The heat stability of milk proteins decreases with a transfer surfaces, which then act as nuclei for deposit
reduction in pH (Foster et al. 1989, Xiong 1992, Corredig formation (Burton 1968, de Jong 1997). The solubility of
and Dalgleish 1996, de Jong et al. 1998). The calcium ions air in milk decreases with heating as well as a reduction in
present in the milk decrease the denaturation temperature of the pressure (de Jong 1997, de Jong et al. 1998). Also the
-Lg, promote aggregation by attaching to -Lg, and formation of air bubbles is enhanced by mechanical forces
enhance the deposition by forming bridges between the induced by valves, expansion vessels, free-falling streams
proteins adsorbed on the heat transfer surface and etc. (de Jong 1997).
aggregates formed in the bulk (Changani et al. 1997, Fouling decreased with increasing turbulence (Belmar-
Christian et al. 2002). It has also been reported that Beiny et al. 1993, Santos et al. 2003). According to
increasing or decreasing the calcium content of milk Paterson and Fryer (1988) and Changani et al. (1997) the
compared with normal milk lowers the heat stability and thickness and subsequently the volume of laminar sublayer
caused more fouling (Roefs and de Kruif 1994). The fat decrease with increasing velocity and as a result the amount
present in milk has little effect on fouling (Visser and of foulant depositing on the heat transfer surface decreases.
Jeurnink 1997). Additives may reduce fouling by Higher flow velocities also promote deposit re-entrainment
enhancing heat stability of milk but they may not be through increased fluid shear stresses (Rakes et al. 1986).
permitted in many countries (Lyster 1970, Skudder et al. Higher turbulence and different flow characteristics are in
1981, Changani et al. 1997). fact found to result in smaller induction period in plate heat
Holding milk for 24 hours before processing results in exchangers compared with tubular heat exchangers
less fouling although further ageing increases fouling (Belmar-Beiny et al. 1993). The reason for this may be the
(Burton 1968, Changani et al. 1997). Prolonged storage of presence of low velocity zones near the contact points
milk for a few days at 5oC may enhance fouling due to the between the adjacent plates. The use of pulsatile flow was
action of proteolytic enzymes (Burton 1968, de Jong 1997). found to mitigate fouling when only the wall region near the
Preheating of milk in holding tubes causes denaturation and heat transfer surface was hot enough to cause the protein

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152 Heat Exchanger Fouling and Cleaning - Challenges and Opportunities [2005], Vol. RP2, Article 23

denaturation and aggregation reactions. The reason was surface microstructure (roughness and other irregularities),
that the fluid spent less time near the wall due to higher presence of active sites, residual materials from previous
mixing (Bradley and Fryer 1992). The pulsations however, processing conditions, and type of stainless steel used
enhanced fouling when the bulk fluid was also hot enough (Jeurnink et al. 1996, Visser and Jeurnink 1997). The
for the protein reactions to take place. modifications of the heat transfer surface characteristics
Temperature of milk in a heat exchanger is probably through electro-polishing, surface coatings etc. may help
the single most important factor controlling fouling (Burton reduce fouling by altering the surface roughness and
1968, Kessler and Beyer 1991, Belmar-Beiny et al. 1993, wettability (changing the polarisation from a hydrophilic
Toyoda et al. 1994, Elofsson et al. 1996, Jeurnink et al. into a hydrophobic state) (Yoon and Lund 1994, Pielinger-
1996, Corredig and Dalgleish 1996, Santos et al. 2003). Schweiger 2001, Beuf et al. 2003, Santos et al. 2001,
Increasing the temperature results in higher fouling. Rosmaninho et al. 2003). Increasing the surface roughness
Beyond 110oC, the nature of fouling will change from type provides a larger effective surface area and results in a
A to type B (Burton 1968). It is worth mentioning that both higher effective surface energy than a smooth surface
the absolute temperature and temperature difference are (Yoon and Lund 1994). As a result, the adhesion of
important for fouling. This means that it is feasible to have deposits with a rough surface would be comparatively
fouling in coolers where the wall temperature is lower than stronger. The affect of different surface coatings tend to be
the bulk temperature. Chen and Bala (1998) investigated less on the deposit formation but more on their adhesion
the effect of surface and bulk temperatures on the fouling of strength (Britten et al. 1988). Magnetic field treatment was
whole milk, skim milk, and whey protein and found that the observed to have no effect on the milk fouling rate (Yoon
surface temperature was the most important factor in and Lund 1994).
initiating fouling. When the surface temperature was less There has been an increasing use of heat exchangers
than 68oC, no fouling was observed even though the bulk that foul comparatively less e.g. fluidised bed heat
temperature was up to 84oC. Chen et al. (2001) predicted exchangers (Klaren 2003), Helixchanger heat exchangers
that mixing caused by in-line mixers can reduce fouling (Master et al. 2003), heat exchangers equipped with
substantially. turbulence promoters (Gough and Rogers 1987) etc.,
however there is little information available about their use
Type and characteristics of heat exchangers in thermal processing of dairy fluids. The use of pulsatile
Plate heat exchangers are commonly used in dairy flow exchanger results in higher mass transfer that may
industry as they offer advantages of superior heat transfer enhance fouling in case the deposition process is mass
performance, lower temperature gradient, higher turbulence, transfer controlled (Bradley and Fryer 1992). The use of
ease of maintenance, and compactness over tubular heat fluid bed heat exchanger was found to reduce the amount of
exchangers. However, plate heat exchangers are prone to fouling and increase the rate of heat transfer as well
fouling due to their narrow flow channels (Delplace et al. (Bradley and Fryer 1992).
1994). Also milk fouling in a heat exchanger is difficult to Direct heating methods like steam injection and steam
completely eliminate, simply due to the fact that the infusion allow to have an optimal selectivity between
temperature of the heat transfer surface needs to be desired (nutritional value) and undesired (surviving micro-
considerably higher than the bulk temperature in order to organisms) product transformations (de Jong et al. 1998).
have efficient heat transfer. Complex hydraulic and thermal These methods result in low fouling rate because the desired
characteristics in plate heat exchangers make it very temperatures are achieved within a very short time due to
difficult to analyze milk fouling. The use of co-current and high heating rates (de Jong 1997). Also high viscous fluids
counter-current flow passages within the same heat can be handled more easily (de Jong et al. 1998). The
exchanger further complicates the problem. absence of heat transfer surface in such a case is also an
The heat transfer surface to which the deposits stick advantage. The resulting dilution however may not be
also affects fouling. However, the surface characteristics desirable. The direct injection of hot air/nitrogen was found
are important only until the surface gets covered with the to give satisfactory performance in concentrating milk
deposits. The surface treatment may be of great benefit for through evaporation of water (Zaida et al. 1987)
fouling removal as fouling would occur after a time delay Microwave heating has been used in numerous
and the strength of the adhesion of the deposits onto the industrial applications for several years due to its
metal surfaces may be weaker, giving way to an easier advantages like faster throughput, better quality, energy
cleaning process. Stainless steel is the standard material saving, less space requirement etc. over conventional
used in the dairy industry. Factors that may affect fouling heating methods (Metaxas and Meredith 1988). However,
of a stainless steel surface are: presence of a chromium limited lifespan of a microwave system can raise doubts
oxide or passive layer, surface charge, surface energy, over its economic viability. A number of studies have been

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Bansal and Chen: 153

reported on heat treatment of milk using microwaves, deposit/fluid interface temperature increases and promotes
however these are based on general quality issues like fouling (Bansal et al. 2005).
nutrients, micro-organisms etc. instead of fouling (Kindle et There are two other issues that may be important in an
al. 1996, Villamiel et al. 1996, Sieber et al. 1996, Thompson ohmic heating process. Better mixing of the fluid may be
and Thompson 1990). required to overcome the wall effect and result in uniform
In induction heating, heat is generated by placing food heating but it may also promote fouling as the foulant is
material inside electric coils. These coils generate transferred easily from the bulk to the surface. Cooling may
oscillating magnetic fields, send electric current through the be employed to reduce the temperatures of electrode
food material, and thus cause heating. Induction heating surfaces that would help control fouling.
produces high local temperatures very quickly but its use
has been limited to materials industry only. Presence of Micro-organisms
Ohmic heating or direct resistance heating is a novel The formation of deposits promotes the adhesion of
heat treatment process where an electrical current is passed micro-organisms to the surface resulting in bio-fouling.
through the milk and heat is generated within the milk to Furthermore, the deposits provide nutrients to micro-
achieve pasteurization or sterilization (Quarini 1995). This organisms ensuring their growth. It is worth mentioning
technique offers the potential of thermal processing of here that most of the processes in industry are carried out at
materials without relying on an inefficient mechanism like temperatures below 100oC. For example, pasteurisation is
conduction of heat from a surface into the fluid. The generally achieved by heating of milk at 72oC for 15
resistance heating technique was used for milk seconds in a continuous flow system. At this temperature
pasteurization in the early 20th century (de Alwis and Fryer only the pathogenic bacteria along with some vegetative
1990). In recent years this technology has been in use cells are killed. A higher temperature of 85oC is required to
again, after being abandoned for a major part of the 20th kill the remaining vegetative cells. Spores are much more
century. APV International Ltd. (England) developed heat-resistant and remain active well beyond this
commercial ohmic heating units for continuous sterilization temperature. However, their inactivation is important for
of food products (Skudder and Biss 1997). Ayadi et al. the products with longer shelf life.
(2003a, b, 2004)) have investigated the performance of a Bio-fouling, either micro-organisms deposition or bio-
plate type ohmic heater for the thermal treatment of dairy film formation, in a heat exchanger raises serious quality
products. concerns. Flint and co-workers have investigated the effect
The major advantages of ohmic heating are: absence of of bio-fouling in dairy manufacturing plants (Flint and
moving parts, non-dependency on thermal conductivity of Hartley 1996, Flint et al. 1997, 1999, 2000). According to
materials, fast and uniform heating, and ability to start/stop Bott (1993), bio-fouling takes place through two different
thermal processing instantaneously. The disadvantages are: mechanisms: deposition of micro-organisms directly on the
deposition and corrosion of electrode surfaces and heat transfer surfaces of the heat exchanger, and
additional safety requirements. Ohmic heating has an deposition/attachment/entrapment of micro-organisms on/in
advantage over microwave processing where processing can the deposit layer forming on the heat transfer surfaces.
be limited by the depth to which energy can penetrate the With the supply of nutrients by the deposits, bacteria
food material (Fryer et al. 1993). multiply. The presence of micro-organisms in the process
Fouling can not be completely eliminated in an ohmic stream and/or deposit layer does not only affect the product
heating process because when milk is heated for the quality, it influences the fouling process as well (Yoo et al.
pasteurization/sterilization, it results in protein denaturation, 2004). Also bacteria can get released into the process fluid
aggregation and deposition. However, since surface due to the hydrodynamic forces and result in increased
temperature is lower due to the generation of heat in the concentration of bacteria downstream. This may also result
bulk, less fouling should take place. However, the in the bacterial growth in areas which otherwise are not
temperature profile changes dramatically when the deposits conducive to bio-fouling. The release pattern of
start attaching to the electrode surfaces (Ayadi et al. 2003b, thermophilic bacteria Bacillus stearothermophilus into the
Bansal et al. 2005). In conventional indirect heating process stream was studied in detail by Chen et al. (1998b)
methods like shell and tube or plate heat exchangers the and Yoo and Chen (2002).
deposit formation lowers the deposit/fluid interface
temperature. In an ohmic heating process some heat is Location of fouling
generated in the deposit layer as well due to its own Protein denaturation and aggregation reactions take
electrical resistance. Also the deposits prevent the outward place as soon as milk is processed thermally. The relative
flow of heat from the bulk fluid. As a result, the amounts of the denatured and aggregated proteins depend
on a number of factors like operating conditions, type and

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154 Heat Exchanger Fouling and Cleaning - Challenges and Opportunities [2005], Vol. RP2, Article 23

design of heat exchanger, properties of the heat transfer improvement of dairy products via ohmic heating processes:
surface etc. The use of an efficient technology may help to thermal and hydrodynamic effect on fouling. Proceedings of
mitigate fouling within a heat exchanger; however the Heat Exchanger Fouling and Cleaning - Fundamentals and
processed milk at the exit of the heat exchanger would still Applications, Santa Fe, USA.
have large amounts of the denatured and aggregated Ayadi M. A., Chopard F., Berthou M. & Leuliet J. C.
proteins. This would result in severe fouling at various (2003b) Ohmic heating unit performance under whey
locations further downstream. Hence controlling fouling proteins fouling. Proceedings of International Conference
within the heat exchanger may not yield effective results Engineering and Food (ICEF9), Montpellier, France.
and an overall strategy may need to be developed to study Ayadi M. A., Leuliet J. C., Chopard F., Berthou M. &
the fouling process over the entire setup (Petermeier et al. Lebouche M. (2004) Continuous ohmic heating unit under
2002). whey protein fouling. Innovative Food Science & Emerging
Technologies, 5 (4) 465-473.
CONCLUSIONS Bansal B., Chen X. D. & Lin S. X. Q. (2005) Skim
Fouling in the dairy industry is affected by a number milk fouling during ohmic heating, Heat Exchanger Fouling
of parameters that can be classified into five major and Cleaning: Challenges and Opportunities, Engineering
categories: a) milk quality, b) operating conditions, c) type Conferences International, Kloster Isree, Germany.
and characteristics of heat exchangers, d) presence of Bell R. W. & Sanders C. F. (1944) Prevention of
micro-organisms, and e) transfer of location where fouling milkstone formation in a high-temperature-short-time heater
takes place. It may not be possible to alter the properties of by preheating milk, skim milk and whey. Journal of Dairy
the milk as they are dependent on the source, collection Science 27 499-504.
schedule, season and many other factors. Lower surface Belmar-Beiny M. T. & Fryer P. J. (1993) Preliminary
temperature and higher flow velocity help to reduce fouling. stages of fouling from whey protein solutions. Journal of
Lowering the surface roughness as well as wettability is Dairy Research 60 467-483.
likely to lower the tendency of the proteins to adsorb onto Belmar-Beiny M. T., Gotham S. M., Paterson W. R.,
the surface. The presence of micro-organisms causes bio- Fryer P. J. & Pritchard A. M. (1993) The effect of Reynolds
fouling. Furthermore, the deposits provide nutrients to the number and fluid temperature in whey protein fouling.
micro-organisms ensuring their growth. The situation gets Journal of Food Engineering 19 119-139.
worse if the micro-organisms are released into the process Beuf M., Rizzo G., Leuliet J. C., Mller-Steinhagen
stream due to its interaction with the deposit layer. The use H., Yiantsios S., Karabelas A. & Benezech T. (2003)
of newer technologies (microwave heating, ohmic heating, Potency of stainless steel modifications in reducing fouling
steam infusion etc.) is gaining momentum because these and in improving cleaning of plate heat exchangers
result in lower fouling, however further research is required processing dairy products. Proceedings of Heat Exchanger
to realise their full potential. Fouling and Cleaning - Fundamentals and Applications,
A significant amount of research has been done on Santa Fe, USA.
fouling; however the underlying fouling mechanisms are Bott T. R. (1993) Aspects of biofilm formation and
not yet fully understood. A part of the problem is the destruction, Corrosion Reviews 11 (1-2) 1-24.
complex nature of milk and the dairy processes. The Bradley S. E. & Fryer P. J. (1992) A comparison of
absence of generalised methodologies and techniques to two fouling-resistant heat exchangers. Biofouling 5 295-
control fouling worsens the problem. Further, concentrated 314.
and joint efforts among industry, research institutes, and Britten M., Green M. L., Boulet M. & Paquin P.
academia are required to combat this serious problem. (1988) Deposit formation on heated surfaces: effect of
interface energetics. Journal of Dairy Research 55 551-562.
REFERENCES Burton H. (1967) Seasonal variation in deposit
Anema S. G. & McKenna A. B. (1996) Reaction formation from whole milk on a heated surface. Journal of
kinetics of thermal denaturation of whey proteins in heated Dairy Research 34 137-143.
reconstituted whole milk. Journal of Agricultural and Food Burton H. (1968) Deposits from whole milk in heat
Chemistry 44 422-428. treatment plant - a review and discussion. Journal of Dairy
Arnebrant T., Barton K. & Nylander T. (1987) Research 35 317-330.
Adsorption of -lactalbumin and -lactoglobulin on metal Bylund G. (1995) Dairy Processing Handbook, Tetra
surfaces versus temperature. Journal of Colloid and Pak Processing Systems AB, Sweden.
Interface Science 119 (2) 383-390. Changani S. D., Belmar-Beiny M. T. & Fryer P. J.
Ayadi M. A., Bouvier L., Chopard F., Berthou M., (1997) Engineering and chemical factors associated with
Fillaudeau L. & Leuliet J. C. (2003a) Heat treatment

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Bansal and Chen: 155

fouling and cleaning in milk processing. Experimental Delplace F., Leuliet J. C. & Tissier J. P. (1994)
Thermal and Fluid Science 14 392-406. Fouling experiments of a plate heat exchanger by whey
Chen J. (2000) Computer Simulation of Whey Protein proteins solutions. Transactions of IChemE (Part C) 72 163-
based Milk Fouling. Master of Engineering Thesis, The 169.
University of Auckland, Auckland, New Zealand. Delplace F., Leuliet J. C. & Levieux D. (1997) A
Chen X. D. & Bala P. (1998) Investigation of the reaction engineering approach to the analysis of fouling by
influences of surface and bulk temperatures upon fouling of whey proteins of a six-channel-per-pass plate heat
milk components onto a stainless steel probe. Proceedings exchanger. Journal of Food Engineering 34 91-108.
of Fouling and Cleaning in Food Processing, Jesus College, Elofsson U. M., Paulsson M. A., Sellers P. &
Cambridge, England, 25-32. Arnebrant T. (1996) Adsorption during heat treatment
Chen X. D., Chen Z. D., Nguang S. K. & Anema S. related to the thermal unfolding/aggregation of -
(1998a) Exploring the reaction kinetics of whey protein lactoglobulin A and B. Journal of Colloid and Interface
denaturation/aggregation by assuming the denaturation step Science 183 408-415.
is reversible. Biochemical Engineering Journal, 2 (1) 63-69. Flint S. & Hartley, N. (1996) A modified selective
Chen X. D., Yoo J., Benjamin A. & Turner M. medium for the detection of pseudomonas species that cause
(1998b) Study of bacteria transportation in model milk spoilage of milk and dairy products. International Dairy
foulant and bacteria emission from milk fouling layer into Journal 6 (2) 223-230.
streams of rinse water, Milk and Cleaning Chemical Flint S. H., Brook J. D., van den Elzen H. & Bremer P.
Solutions, Proceedings of Conference on Fouling and J. (1997) Biofilms in dairy manufacturing plant a threat to
Cleaning in Food Processing 98, Edited by D. I. Wilson, P. product quality. The Food Technologist (New Zealand) 27
J. Fryer, and A. P. M. Hasting, Jesus College, Cambridge, (2) 61-64.
England 79-96. Flint S. H., van den Elzen H., Brooks J. D. & Bremer
Chen X. D., Chen J. & Wilson D. I. (2001) Modelling P. J. (1999) Removal and inactivation of thermo-resistant
whey protein based fouling of heat exchangers further streptococci colonising stainless steel, International Dairy
examining the deposition mechanisms. Proceedings of Heat Journal 9 (7) 429-436.
Exchanger Fouling Fundamental Approaches & Technical Flint S. H., Brooks J. D. & Bremer P. J. (2000)
Solutions, Davos, Switzerland. Properties of the stainless steel substrate influencing the
Christian G. K., Changani S. D. & Fryer P. J. (2002) adhesion of thermo-resistant streptococci, Journal of Food
The effect of adding minerals on fouling from whey protein Engineering 43 (4) 235-242.
concentrate development of a model fouling fluid for a Fonterra Co-Operative Group (www.fonterra.com)
plate heat exchanger. Transactions of IChemE (part C) 80 (2004) New Zealand.
231-239. Foster, C. L., Britten M. & Green M. L. (1989) A
Corredig M. & Dalgleish D. G. (1996) Effect of model heat-exchanger apparatus for the investigation of
temperature and pH on the interactions of whey proteins fouling of stainless steel surfaces by milk I. deposit
with casein micelles in skim milk. Food Research formation at 100oC. Journal of Dairy Research 56 201-209.
International 29 (1) 49-55. Fryer P. J. & Belmar-Beiny M. T. (1991) Fouling of
Dalgleish, D. G. (1990) Denaturation and aggregation heat exchangers in the food industry: a chemical
of serum proteins and caseins in heated milk. Journal of engineering perspective. Trends in Food Science &
Agricultural and Food Chemistry 38 (11) 1995-1999. Technology 33-37.
de Alwis A. A. P. & Fryer P. J. (1990) The use of Fryer P. J., de Alwis A. A. P., Koury E., Stapley A. G.
direct resistance heating in the food industry. Journal of F. & Zhang L. (1993) Ohmic processing of solid-liquid
Food Engineering 11 3-27. mixtures: heat generation and convection effects. Journal of
de Jong P., Bouman, S. & van der Linden, H. J. L. J. Food Engineering 18 101-125.
(1992) Fouling of heat transfer equipment in relation to the Fung L., McCarthy O. J. & Tuoc T. K. (1998) The
denaturation of -lactoglobulin. Journal of the Society of effect of fat globule membrane damage on fouling of whole
Dairy Technology 45 3-8. milk. Fouling and Cleaning in Food Processing '98, Jesus
de Jong P. (1997) Impact and control of fouling in College, Cambridge, UK 33-38.
milk processing. Trends in Food Science and Technology 8 Georgiadis M. C., Rotstein G. E. & Macchietto S.
401-405. (1998) Optimal design and operation of heat exchangers
de Jong P., van der Horst H. C. & Waalewijn R. under milk fouling. AIChE Journal 44 (9) 2099-2111.
(1998) Reduction of protein and mineral fouling. Fouling Gillham C. R., Fryer P. J., Hasting A. P. M. & Wilson
and Cleaning in Food Processing '98, Jesus College, D. I. (2000) Enhanced cleaning of whey protein soils using
Cambridge, UK 39-46. pulsed flows. Journal of Food Engineering 46 199-209.

Produced by The Berkeley Electronic Press, 2009

156 Heat Exchanger Fouling and Cleaning - Challenges and Opportunities [2005], Vol. RP2, Article 23

Gotham S. M., Fryer P. J. & Pritchard A. M. (1992) - Metaxas A. C. & Meredith R. J. (1988) Industrial
lactoglobulin denaturation and aggregation reactions and Microwave Heating, Published by Peter Peregrinus Ltd.,
fouling deposit formation: a DSC study. International London, United Kingdom 296-321.
Journal of Food Science and Technology 27 313-327. Mottar J. & Moermans R. (1988) Optimization of the
Gough M. J. & Rogers J. V. (1987) Reduced fouling forewarming process with respect to deposit formation in
by enhanced heat transfer using wire matrix radial mixing indirect ultra high temperature plants and the quality of
elements. AIChE Symposium Series - 257 16-21. milk. Journal of Dairy Research 55 563-568.
Hege W. U. & Kessler H.-G. (1986) Deposit formation Mller-Steinhagen H. (1993) Fouling: the ultimate
of protein containing dairy liquids. Milchwissenschaft 41 challenge for heat exchanger design. Proceedings of the
356-360. Sixth International Symposium on Transport Phenomena in
Jeurnink T., Verheul M., Stuart M. C. & de Kruif C. Thermal Engineering, Seoul, Korea 811-823.
G. (1996) Deposition of heated whey proteins on a Mulvihill D. M. & Donovan M. (1987) Whey proteins
chromium oxide surface. Colloids and Surfaces B: and their thermal denaturation - a review. Irish Journal of
Biointerfaces 6 291-307. Food Science and Technology 11 43-75.
Karlsson C. A.-C., Wahlgren M. C. & Trgrdh A. C. Newstead D. F., Groube G. F., Smith A. F. & Eiger R.
(1996) -Lactoglobulin fouling and its removal upon N. (1998) Fouling of UHT plants by recombined and fresh
rinsing and by SDS as influenced by surface characteristics, milk: some effects of preheat treatment. Fouling and
temperature and adsorption time. Journal of Food Cleaning in Food Processing '98, Jesus College, Cambridge,
Engineering 30 43-60. UK 17-24.
Kessler H.-G. & Beyer, H.-J. (1991) Thermal Paterson W. R. & Fryer P. J. (1988) A reaction
denaturation of whey proteins and its effect in dairy engineering approach to the analysis of fouling. Chemical
technology. International Journal of biological Engineering Science 43 (7) 1714-1717.
macromolecules 13 165-173. Petermeier H., Benning R., Delgado A., Kulozik U.,
Kindle G., Busse A., Kampa D., Meyer-Konig U. & Hinrichs J. & Becker T. (2002) Hybrid model of the fouling
Daschner F. D. (1996) Killing activity of microwaves in process in tubular heat exchangers for the dairy industry.
milk. Journal of Hospital Infection 33 (4) 273-278. Journal of Food Engineering 55 9-17.
Klaren D. G. (2003) Improvements and new Pielinger-Schweiger S. (2001) Electrochemical and
developments in self-cleaning heat transfer leading to new chemical polishing of heat exchangers. Proceedings of Heat
applications. Heat Exchanger Fouling and Cleaning: Exchanger Fouling Fundamental Approaches & Technical
Fundamentals and Applications, Santa Fe, New Mexico, Solutions, Davos, Switzerland.
USA.
Lalande, M. & Ren F. (1988) Fouling by milk and Quarini G. L. (1995) Thermalhydraulic aspects of the
dairy product and cleaning of heat exchanger surfaces. ohmic heating process. Journal of Food Engineering 24
Fouling Science and Technology, L. F. Melo, T. R. Bott, 561-574.
and C. A. Bernardo, eds., Kluwer, Amsterdam, Netherlands Rakes P. A., Swartzel K. R. & Jones V. A. (1986)
557-573. Deposition of dairy protein-containing fluids on heat
Lalande M., Tissier J.-P. & Corrieu G. (1985) Fouling exchanger surfaces. Biotechnology Progress 2 (4) 210-217.
of heat transfer surfaces related to -lactoglobulin Roefs S. P. F. M. & de Kruif K. G. (1994) A model for
denaturation during heat processing of milk. Biotechnology the denaturation and aggregation of -lactoglobulin.
Progress 1 (2) 131-139. European Journal of Biochemistry 226 883-889.
Lund D. B. & Bixby B. (1975) Fouling of heat Rosmaninho R., Rizzo G., Mller-Steinhagen H. &
exchanger surfaces by milk. Process Biochemistry 10 52- Melo L. F. (2003) The influence of bulk properties and
55. surface characteristics on the deposition process of calcium
Lyster R. L. J. (1970) The denaturation of - phosphate on stainless steel. Proceedings of Heat Exchanger
lactalbumin and -lactoglobulin in heated milk. Journal of Fouling and Cleaning - Fundamentals and Applications,
Dairy Research 37 233-243. Santa Fe, USA.
Master B. I., Chunangad K. S. & Pushpanathan V. Ruegg M., Moor U. & Blanc B. (1977) A calorimetric
(2003) Fouling mitigation using helixchanger heat study of the thermal denaturation of whey proteins in
exchangers. Heat Exchanger Fouling and Cleaning: simulated milk ultrafiltrates. Journal of Dairy Research 44
Fundamentals and Applications, Santa Fe, New Mexico, 509-520.
USA. Santos O., Nylander T., Paulsson M. & Trgrdh C.
(2001) Adsorption behaviour of -Lactoglobulin on
different types of stainless steel surfaces. Proceedings of

http://services.bepress.com/eci/heatexchanger2005/23
Bansal and Chen: 157

Heat Exchanger Fouling Fundamental Approaches & on milk fouling. Journal of Food Science 59 (5) 964-969,
Technical Solutions, Davos, Switzerland. 980.
Santos O., Nylander T., Rizzo G., Mller-Steinhagen Zaida A. H., Sarma S. C., Grover P. D. & Heldman D.
H., Trgrdh C. & Paulsson M. (2003) Study of whey R. (1987) Milk concentration by direct contact heat
protein adsorption under turbulent flow rate. Proceedings of exchange, Journal of Food Process Engineering 9 (1) 63-79.
Heat Exchanger Fouling and Cleaning - Fundamentals and
Applications, Santa Fe, USA.
Schreier P. J. R. & Fryer P. J. (1995) Heat exchanger
fouling: a model study of the scaleup of laboratory data.
Chemical Engineering Science 50 (8) 1311-1321.
Sieber R., Eberhard P. & Gallmann P. U. (1996) Heat
treatment of milk in domestic microwave ovens.
International Dairy Journal 6 (3) 231-246.
Skudder P. J., Thomas E. L., Pavey J. A. & Perkin A.
G. (1981) Effects of adding potassium iodate to milk before
UHT treatment. I. Reduction in the amount of deposit on the
heated surfaces. Journal of Dairy Research 48 99-113.
Skudder P. & Biss C. (1987) Aseptic processing of
food products using ohmic heating. The Chemical Engineer
26-28.
Thompson J. S. & Thompson A. (1990) In-home
pasteurization of raw goat's milk by microwave treatment.
International Journal of Food Microbiology 10 (1) 59-64.
Toyoda I., Schreier P. J. R. & Fryer P. J. (1994) A
computational model for reaction fouling from whey protein
solutions. Proceedings of Fouling Cleaning in Food
Processing, Cambridge, England 222-229.
Treybal R. E. (1981). Mass Transfer Operations,
McGraw-Hill Book Company, 3rd edition.
van Asselt A. J., Vissers M. M. M., Smit F. & de Jong
P. (2005) In-line control of fouling. Proceedings of Heat
Exchanger Fouling and Cleaning - Challenges and
Opportunities, Engineering Conferences International,
Kloster Irsee, Germany.
Villamiel M., Corzo N., Martinez-Castro I. & Olano,
A. (1996) Chemical changes during microwave treatment of
milk. Food Chemistry 56 (4) 385-388.
Visser J. & Jeurnink Th. J. M. (1997) Fouling of heat
exchangers in the dairy industry. Experimental Thermal and
Fluid Science 14 407-424.
Xiong Y. L. (1992) Influence of pH and ionic
environment on thermal aggregation of whey proteins.
Journal of Agricultural and Food Chemistry 40 380-384.
Yoo J. & Chen X. D. (2002) An emission pattern of a
thermophilic bacteria attached to or imbedded in porous
catalyst, International Journal of Food Microbiology 72 11-
21.
Yoo J., Hardin M. T. & Chen X. D. (2004) The
influence of milk composition on the growth of bacillus
stearothermophilus, Biotechnology and Biological
Engineering (Accepted).
Yoon J. & Lund D. B. (1994) Magnetic treatment of
milk and surface treatment of plate heat exchangers: effect

Produced by The Berkeley Electronic Press, 2009