WO2009091268A1

WO2009091268A1 - Improved anhydrous milk fat production plant

Info

Publication number: WO2009091268A1
Application number: PCT/NZ2009/000006
Authority: WO
Inventors: Christopher Ross Titoki Burt; Arnold Friedhelm Uphus
Original assignee: Westfalia Separator Nz Limited
Priority date: 2008-01-16
Filing date: 2009-01-15
Publication date: 2009-07-23

Abstract

A method of inhibiting and/or disrupting bacterial and/or biofilm and/or thermophile growth within heat exchangers used in the manufacture of anhydrous milk fat or butter or butter oil by thermal cycling of at least one process unit in the system.

Description

IMPROVED ANHYDROUS MILK FAT PRODUCTION PLANT

FIELD OF THE INVENTION

The present invention relates to an improved AMF production plant, more particularly, though not solely, to a method of inhibiting and/or disrupting bacterial and/or biofilm and/or thermophile growth within a process unit, and in particular, though also not solely, to a method of inhibiting and/or disrupting bacterial and/or biofilm and/or thermophile growth within heat exchangers used in the manufacture of anhydrous milk fat (AMF) or butter or butteroil.

BACKGROUND TO THE INVENTION

Heat exchangers are used throughout many industries to raise or lower the temperature of a process stream. In the food processing industry, as in many industries, changes in the temperature of a process stream can be useful in allowing variation in the characteristics of the material being processed for further treatment. Altering the temperature of a process stream may also be desirable to preserve the characteristics of product.

Pasteurisation is one example of using a heat exchanger to alter the characteristics of a food process stream. In such a process, the food stream (i.e. milk) is heated to a minimum temperature of between 65° and 100ºC for a given period of time to inactivate enzymes and reduce the population of micro-organisms.

However, many food processing operations utilise heat exchange units which, by the nature and/or requirements of the food stream being processed operate at temperatures less than that of a Pasteurisation process. Heat exchangers may also operate using the heat provided from upstream or downstream process operations to impart (or extract) heat from another process stream passing through the heat exchanger. The process optimisation of energy within a process plant is particularly beneficial in achieving increased operational efficiencies. It is also desirable to minimise the heating and/or cooling requirements of a process plant from external energy sources. As a consequence of this, many process streams in a process plant are used in heat exchangers where necessary to impart or extract energy to another process stream. A problem of operating heat exchangers at temperatures less than the parameters of elevated temperature and for sufficient times which are required for Pasteurisation means that growth of live cultures on the internal surfaces of the heat exchanger may occur. Such growth may occur particularly in heat exchangers which provide both suitable temperatures and an environment which bacteria or other pathogens may thrive in. Suitable environments may be those which contain sufficient nutrients to allow bacterial cultures to grow, such as water and a supply of carbohydrate. Food processing operations must be particularly vigilant in the cleaning of such bacterial cultures from within heat exchangers as increased levels of bacteria in food may result in reduced food quality issues. Clearly this is undesirable.

In addition, bacterial growth within heat exchangers can adversely impact the flow characteristics and efficiency of heat exchange from one process fluid to another. Some examples of undesirable growth cultures and organisms (i.e. pathogens) particularly prevalent in the dairy processing industry are bacteria, fungi such as yeasts and moulds, and bacteriophages. Temperature resistant growth cultures may survive a Pasteurisation process and thus still remain present with the dairy component which undergoes further processing (for example cream in an AMF production facility).

Many systems have been developed to combat bacterial growth. Many of these previous solutions have involved the use of chemical cleaning, or ultrasonic cleaning of the process equipment to dislodge and reduce the fouling of the heat exchanger. However, these solutions often require that the heat exchanger be removed from service. Removal of service of a piece of process equipment results in unwanted down-time. Of course, there are situations where a process fluid is alternately split in its feed between two or more heat exchangers, such that as the first heat exchanger becomes fouled the feed flow is directed to the second heat exchanger and so on whilst the fouled heat exchanger undergoes a cleaning operation before resuming operation. However, this system requires additional capital equipment. It does not reduce the requirement to clean a heat exchanger in any way.

Reduction in the downtime of any processing operation is always sought so as to increase operation efficiencies. In the processing of anhydrous milk fat (AMF), current industry technologies mean that run times of around 9 hours are achieved before the process must be halted and the heat exchangers cleaned. The cleaning removes the build-up of bacterial film growth from within the heat exchangers and reduces fouling. Usually, it is desired that the 9 hour run time is performed on a continuous basis. If it was possible to increase the run time to longer than 9 hours, then this would enable the achievement of significant processing advantages. It would also allow greater stability of process control and allow further optimisation of many of the pieces of equipment run during this period as well as the reduction raw feed materials (such as wash water) to the system as a reduced number of start-up and end processes would be carried out in processing the whole of the feed stock.

Reference by incorporation in this specification is also made to the "The Tetra Pak Dairy Processing Handbook", Tetra Pak Processing Systems AB, second revised edition, published 2003.

OBJECT OF THE INVENTION

It is therefore an object of the present invention to provide a process which reduces or helps minimise the need to undertake cleaning of a heat exchanger and which will go at least some way towards addressing the foregoing problems or which will at least provide the industry with a useful choice.

SUMMARY OF THE INVENTION

The inclusion of reference from the drawings in this portion of the description is provided to aid clarity only and is not to be taken as so limiting the scope of the invention. In a first aspect, the present invention may broadly consist in a method of inhibiting and/or disrupting bacterial and/or biofilm and/or thermophile growth within a process unit by thermal cycling of the temperature of the unit.

Preferably, the process unit may be a heat exchanger.

Preferably, the heat exchanger may be of a plate-type or shell- and tube-type configuration. The heat exchanger may be operated in a co-flow or counter-flow manner.

In a second aspect, the present invention may broadly consist in a method for inhibiting and/or disrupting bacterial and/or biofilm and/or thermophile growth in a heat exchanger, the heat exchanger comprising a part of a system for manufacture of anhydrous milk fat (hereinafter "AMF") comprising the steps of: providing a feed stream of cream (2) from a cream source (e.g. a cream balance tank (CBT)) to a first heat exchanger (HX1) and elevating the cream stream temperature, feeding the elevated temperature cream stream to a first separator (SEP1) and substantially separating the elevated temperature cream stream into a light phase (an oil rich phase) stream (LP1) and a heavy phase (an emulsion rich phase) stream (HP1), feeding the light phase stream (LP1) to a first balance tank (BT1), accumulating at least a portion of the stream (the light phase stream (LP1)) fed to first balance tank (BT1),

such that, after a predetermined period of operation the first heat exchanger (HX1) is subjected to a thermal cycle treatment,. The thermal cycle treatment comprises recycling at least a portion of the feed stream of cream (2) fed to the first heat exchanger (HX1) from the cream source (e.g. cream balance tank (CBT)) about the first heat exchanger (HX1) and elevating the operational temperature of the first heat exchanger (HX1 ) to a thermal cycling temperature and maintaining the thermal cycle treatment for a predetermined period of time.

The accumulated light phase stream (LP1) in the first balance tank (BT1) is used to feed downstream process operations.

In a third aspect, the present invention may broadly consist in a method for inhibiting and/or disrupting bacterial and/or biofilm and/or thermophile growth in a heat exchanger, the heat exchanger comprising a part of a system for manufacture of anhydrous milk fat (hereinafter "AMF") comprising the steps of: providing a feed stream of cream (2) from a cream source (e.g. a cream balance tank (CBT)) to a first heat exchanger (HX1) and elevating the cream stream (2) temperature, feeding the elevated temperature cream stream to a first separator (SEP1) and substantially separating the feed stream of cream (2) into a light phase (an oil rich phase) stream (LP1) and a heavy phase (an emulsion rich phase) stream (HP1), feeding the light phase stream (LP1) to a second separator (SEP2) and separating the light phase stream (LP1) into a light phase (an oil rich phase) stream (LP2) and a heavy phase (an emulsion rich phase) stream (HP2), the heavy phase stream (HP2) being fed to a second balance tank (BT2), accumulating at least a portion of the stream(s) fed to the second balance tank (BT2), and: a. carrying out a separation of the heavy phase stream (HP2) in a third separator (SEP3) yielding a light phase stream (LP3) and a heavy phase stream (HP3) and passing the heavy phase stream (HP3) through a second heat exchanger (HX2), or b. passing the heavy phase stream (HP2) from the second balance tank (BT2) through a second heat exchanger (HX2),

such that, after a predetermined period of operation the second heat exchanger (HX2) is subjected to a thermal cycle treatment. The thermal cycle treatment comprises recycling at least a portion of the stream(s) (HP2) fed to the second balance tank (BT2) about the second heat exchanger (HX2) and elevating the operational temperature of the second heat exchanger (HX2) to a thermal cycling temperature and maintaining the thermal cycle treatment for a predetermined period of time.

In a fourth aspect, the present invention may broadly consist in a method for inhibiting and/or disrupting bacterial and/or biofilm and/or thermophile growth in a heat exchanger or exchangers, the heat exchanger(s) comprising a part of a system for manufacture of anhydrous milk fat (hereinafter "AMF") comprising the steps of: providing a feed stream of cream (2) from a cream source (e.g. a cream balance tank (CBT)) to a first heat exchanger (HX1 ) and elevating the cream stream (2) temperature, feeding the elevated temperature to a first separator (SEP1) and substantially separating the elevated temperature cream stream into a light phase (an oil rich phase) stream (LP1) and a heavy phase (an emulsion rich phase) stream (HP1), and feeding the light phase stream (LP1) to a first balance tank (BT1), accumulating at least a portion of the light phase stream (LP1) fed to the first balance tank for downstream processing operations, and feeding the light phase stream (LP1) to a second separator (SEP2) and separating the light phase stream (LP1) into a light phase (an oil rich phase) stream (LP2) and a heavy phase (an emulsion rich phase) stream (HP2), the heavy phase stream (HP2) being fed to a second balance tank (BT2), accumulating at least a portion of the stream(s) fed to the second balance tank (BT2), and then either: a. carrying out a separation of the heavy phase stream (HP2) in a third separator (SEP3) yielding a light phase stream (LP3) and a heavy phase stream (HP3) and passing the heavy phase stream (HP3) through a second heat exchanger (HX2), or b. passing the heavy phase stream (HP2) from the second balance tank (BT2) through a second heat exchanger (HX2),

such that, after a predetermined period of operation the first heat exchanger (HX1) and the second heat exchanger (HX2) are each subjected to a thermal cycle treatment. The thermal cycle treatment comprises recycling at least a portion of the feed stream of cream (2) fed to the first heat exchanger (HX1) and recycling at least a portion of the feed to the second balance tank (BT2) (HP2, HP3) about the second heat exchanger (HX2), and elevating the temperature of the first and the second heat exchangers (HX1 , HX2) from their respective operational temperatures to a thermal cycling temperature and maintaining the thermal cycle treatment for a predetermined period of time.

In a fifth aspect, the present invention may broadly consist in a system for inhibiting and/or disrupting bacterial and/or biofilm and/or thermophile growth within a process unit by thermal cycling of the temperature of the unit.

In a sixth aspect, the present invention may broadly consist in a system for inhibiting and/or disrupting bacterial and/or biofilm and/or thermophile growth in a heat exchanger, the heat exchanger comprising a part of a system for manufacture of anhydrous milk fat (hereinafter "AMF") comprising implementing the method of any one of aspects one through four above.

Preferably, during a recycle mode or thermal cycling mode of operation, the stream fed to the process unit or heat exchanger which is not being recycled is reduced to a minimum flow rate or flow is stopped completely. Such operation may allow a process unit or heat exchanger in a thermal cycling mode to be more quickly elevated to a desired thermal cycling temperature. Advantageously, when the process unit or heat exchanger(s) is/are in a thermal cycling mode, the feed cream stream (2) which is recycling about the first heat exchanger (HX1) is also being heated in the heat exchanger. Fresh feed of cream from the cream source, such as the cream balance tank (CBT), is not required as the cream feed stream (2) is being recycled about the heat exchanger. As a result of this, once the first heat exchanger comes out of a thermal cycling mode of operation the feed cream will have already been elevated in temperature and so the heating requirements for the first heat exchanger needed to impart energy to the cream feed stream (2) for subsequent supply to the first separator (SEP1) are temporarily reduced.

Once the cream source or feed cream balance tank (CBT) supplies fresh cream feed to the process unit or first heat exchanger (HX1), the heating requirements of the first heat exchanger (HX1) will return (rise) to previous "normal" (non-thermal cycling) operational processing conditions/levels. In one example, the cream feed source may preferably supply cream at a temperature in the range of between substantially 3°C to substantially 15ºC, more preferably substantially 6°C to substantially 10ºC, even more preferably substantially 6°C to substantially 10°C.

Preferably, the process unit processes at least one liquid stream, such as for example a liquid food stream or an animal milk stream. More preferably the liquid stream being processed may be a dairy-derived material, such as cream. The process unit or heat exchanger(s) may be fed by two liquid food streams, one being provided on the heating side of the exchanger and the other on the cooling side of the exchanger. In this manner energy efficiencies about the AMF plant may be improved.

Preferably, thermal cycling may be an increase in the operational temperature of the process unit for a predetermined period of time.

Preferably, the increase in temperature of the process unit is effected by recycling at least one of the liquid streams through the process unit. More preferably during recycling or thermal cycling mode the at least one recycled liquid stream is additionally heated by a heating means.

Preferably, the predetermined period of thermal cycling may be between from substantially 20 seconds to substantially 45 minutes. More preferably, the period of thermal cycling may be in the range of from substantially 30 seconds to substantially 30 minutes, even more preferably in the range of from substantially 1 minute to substantially 15 minutes. Further preferred ranges for the period of thermal cycling may be in the range of from substantially 2 minutes to substantially 10 minutes. Most preferred may be a period of thermal cycling in the range of from substantially 2 minutes to substantially 5 minutes.

Preferably, the period of thermal cycling may take place after a period of operational processing, the period of operational processing being in the range of from substantially 5 minutes to 4 hours, more preferably in the range of from 10 minutes to substantially 3 hours, even more preferably of from substantially 15 minutes to substantially 120 minutes. Even more preferred the period of thermal cycling may take place after the period of operational processing being in the range of from substantially 25 minutes to substantially 90 minutes, most preferably in the range of from substantially 45 minutes to substantially 60 minutes.

Preferably, thermal cycling may be undertaken such that the process unit or heat exchanger temperature is elevated to a thermal cycling temperature which is sufficient to disrupt and/or inhibit bacterial and/or biofilm and/or thermophile growths/multiplication.

Thermal cycling of the process unit or heat exchanger may be utilised to adversely impact upon the growth rates of a majority or at least some of the problematic bacteria and/or biofilms and/or thermophile types which may grow within the unit or exchanger, depending upon the liquid stream being processed. More preferred is that thermal cycling may be undertaken at elevated temperatures above the processing or operational temperatures of between substantially 50ºC to 100ºC, more preferably to elevated thermal cycling temperatures of between substantially 55ºC to substantially 9OºC. Most preferably thermal cycling may be undertaken at elevated thermal cycling temperatures in the range of from between substantially 6OºC to 80°C. Advantageously, thermally cycling the heat exchanger to such elevated temperatures allows shortened periods of thermal cycling to be undertaken which are suitably efficacious to effect the inhibition/disruption of growth characteristics of bacteria/biofilms/cultures within the process unit(s)/heat exchanger(s).

Preferably, in the periods of operational processing (no thermal cycling of the process unit), the input feed rate to the first balance tank (BT1) is greater than the output flow rate. More preferably, this first balance tank (BT1) may be utilised to provide at least some storage of the feed stream provided to it, such that the quantity of material held within the first balance tank (BT1) increases and a portion of the feed is allowed to accumulate.

The period of thermal cycling may be determined or limited by the time taken for a low level volume in the first balance tank (BT1 ) to be reached and/or for the first balance tank (BT1) to substantially empty and/or for the quantity of material held within the first balance tank (BT1) to be reduced to a set point. In the event that a minimum low level of material in the first balance tank (BT1) is reached, the process may be controlled to place the process into appropriate recycle loops to preferably prevent any process device from "running dry" from a lack of an input flow. Alternatively, when a low tank level is reached the thermal cycling of the process unit/heat exchanger may be stopped and operational conditions of fresh feed cream stream (2) supplied to the heat exchanger reinitiated for subsequent processing in the first separator (SEP1).

Advantageously, the quantity of material which is utilised in the recycle stream to the process unit/heat exchanger(s) is kept to a minimum to reduce energy requirements needed to enable elevation of the temperature of the unit/exchanger to the desired thermal cycling temperature from operational temperatures.

Preferably, during operational processing (or no thermal cycling of the process unit) the cream stream is heated in the processing unit or first heat exchanger (HX1) to an output temperature of not more than substantially 8OºC, more preferably to not more than substantially 75°C, most preferably to not more than substantially 65ºC. Most preferably the cream stream is heated to an output temperature in the range of between substantially 55ºC to substantially 65ºC.

Preferably, the heavy phase stream (HP1) from the first separator (SEP1) may be discharged to a separator (SEP4) to yield a heavy phase stream (HP4) and a light phase stream (LP4). More preferably, the heavy phase stream (HP4) may be a buttermilk or an α-serum stream or a precursor thereof. The light phase stream (LP4) may be returned to the cream balance tank (CBT) for processing once again, or may be sent to further processing operations, for example to the second balance tank (BT2) for feed to a third separator (SEP3) or a second heat exchanger (HX2).

Preferably, the heavy phase stream (H P2) from the second separator (SEP2) may be a buttermilk or an β-serum stream, or a precursor thereof. Preferably, the light phase stream (LP2) from the second separator (SEP2) may be discharged to a further separator (SEP5). This further separator (SEP5) may optionally comprise or solely utilise a vacuum system or flash separator. A light phase stream (LP5) discharged from the further separator (SEP5) may be a butteroil. On the other hand, preferably a heavy phase stream (HP5) discharged from the further separator (SEP5) may be fed to the second balance tank (BT2) and processed through the second heat exchanger (HX2) and/or fed through the third separator (SEP3). A heavy phase stream (HP3) and a light phase stream (LP3) may be yielded. The heavy phase stream (HP3) may be processed through the second heat exchanger (HX2) to yield a buttermilk or an β- serum stream, or a precursor thereof.

Preferably, a phase inverter or a homogeniser (3) phase inverts or homogenises the light phase stream (LP1) prior to feeding the light phase stream (LP1) to the second separator (SEP2).

Preferably, a heat exchanger elevates the temperature or controls the temperature of the light phase stream (LP2) to a set point temperature prior to feeding the light phase stream (LP2) to the further separator (SEP5).

Preferably, thermal cycling takes place substantially at the heat transfer surfaces within the process unit or heat exchanger(s). More preferably, the heat transfer surfaces within the process unit or heat exchanger(s) are those surfaces in direct contact with any one of or all of the following: the cream stream, the light phase stream(s) (LP), the heavy phase stream(s) (HP).

Preferably, the process unit or heat exchanger(s) may additionally comprise external heating means or cooling means. For example, electrical, steam or hot water heating facilities and/or cooling facilities provided via chilled water or electrical coolers may supplement the heating or cooling requirements of the process unit or heat exchanger(s).

Preferably, the process unit or heat exchanger has two sources of feed. One source is fed to a side of the unit/exchanger requiring heating, the other source is fed to the side of the unit/exchanger requiring cooling. Heat exchange takes place via heat transfer surfaces. During thermal cycling of the unit/heat exchanger, the source of fed providing cooling to the unit/exchanger is preferably minimised, stopped or at least reduced to sufficient flow that allows the unit/exchanger to be elevated in temperature to the desired thermal cycling temperature effective to inhibit and/or disrupt the growth and/or multiplication of bacteria and/or biofilm(s) and/or thermophiles.

More specifically, in one preferred embodiment, the heavy phase stream (HP4 stream or α-serum stream) can be fed to the first heat exchanger to provide heat exchange and help to pre-heat the cream feed stream (2) during operational conditions. During recycle mode or thermal cycling mode it is preferred that fed of the heavy phase stream (HP) from a fourth separator (SEP4) is minimised or halted. Such a reduced flow condition may become inherent once the first heat exchanger is placed into a thermal cycling mode due to reduced (or no) flow conditions to the first separator.

In the embodiment above the reduced (or no) flow condition may be preferred as this allows the side of the process unit or heat exchanger through which the HP4 stream/ α- serum stream passes to be elevated to the desired thermal cycling temperature. Such a condition is preferred during thermal cycling.

Preferably, the cream stream is provided from a cream storage facility.

Preferably, the method as described above is incorporated into a system of manufacturing anhydrous milk fat (hereinafter "AMF").

For the purposes of this specification, reference to "AMF" also encompasses anhydrous butteroil or butteroil products. These products are obtained exclusively from milk, cream by almost complete removal of water and fat-free dry matter.

Butteroil may be defined as a high fat content product derived from the AMF processing of a milk or dairy derived product, such as cream.

Buttermilk may be defined as a low fat content product derived during manufacture of AMF from a milk or dairy derived product, such as cream. Buttermilk may comprise two streams, referred to as an α-serum or an β-serum stream.

"Cream" may be defined as a fat rich component. More specifically, it may be defined as a portion of a milk which is rich in milk fat or a portion of a milk into which fat has been gathered/concentrated. In one example, a typical composition of a cream may comprise: Water: 45.45% - 68.2%

Fat: 25% - 60 %

Protein: 1.69% - 2.54%

Lactose: 2.47% - 3.71%

Ash: 0.37% - 0.56%

Total Solids: 31.8% - 54.55% Solids not fat: 4.55% - 6.80%

Heavy phase stream may be defined as a stream rich in water and may include an oil-in- water emulsion component. Such a stream derived from a separator has a lower concentration of oil/fat than the corresponding light phase stream derived from the same separator.

Light phase steam may be defined as an oil rich stream. Such a stream derived from a separator has a higher concentration of oil/fat than the corresponding heavy phase stream derived from the same separator.

Milk may be defined as a nutrient-rich liquid secreted by the mammary glands of female mammals (including monotremes). For the purposes of this specification, most preferred is the milk derived from cows and goats.

Thermophile can be defined as any organism which is able to live and multiply at temperatures in the range of between approximately 20ºC to 60ºC.

Biofilm(s) can be defined as the growth of an organism or culture, such as a thermophile upon a surface(s).

The "operational temperature" of a heat exchanger or process unit can be defined, for the purposes of this specification, as the average temperature of the input temperature and output temperature of a stream passing through the heat exchanger under operational processing conditions. It will be appreciated that there will thus be two operational temperatures for each heat exchanger where there are two stream sources being fed to a heat exchanger (i.e. an average operational temperature on the heating side and an average operational temperature on the cooling side of the heat exchanger). The "thermal cycling temperature" of a heat exchanger or process unit can be defined, for the purposes of this specification, as the average temperature of the input temperature and output temperature of a stream passing through the heat exchanger when the process unit or heat exchanger is in a recycle or thermal cycling mode. It should be appreciated that in preferred embodiments, where the heat exchanger has two stream sources passing through the heat exchanger (one on a heating side and one of a cooling side), both such sides of the heat exchanger are elevated in temperature during a thermal cycling or recycle mode. Thus, the thermal cycling temperature may be defined as being an elevated average temperature for each side of the heat exchanger, the elevated temperature being sufficient to at least substantially inhibit and/or disrupt the growth of bacteria and/or biofilm and/or thermophiles growing within the heat exchanger.

The term "comprising" as used in this specification means "consisting at least in part of. When interpreting each statement in this specification that includes the term "comprising", features other than that or those prefaced by the term may also be present. Related terms such as "comprise" and "comprises" are to be interpreted in the same manner.

In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such external documents is not to be construed as an admission that such documents, or such sources of information, in any jurisdiction, are prior art, or form part of the common general knowledge in the art.

This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

The invention consists in the foregoing and also envisages constructions of which the following gives examples only. BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will be described by way of example only and with reference to the drawings, in which:

Figure 1 illustrates a process flow diagram (PFD) of a typical AMF manufacturing operation.

Figure 2 is the same PFD as Figure 1 but indicates the regions A and B of the process to which the present invention may be applied.

Figure 3 is one embodiment of the present invention demonstrating a recycle (RS) on a heat exchanger used in a portion of an AMF manufacturing operation.

Figure 4 is a further embodiment of the present invention demonstrating a recycle system (RS) with optional recycle stream (RS1)on a heat exchanger used in a portion of an AMF manufacturing operation.

Figure 5 is an example of a simplified process flow in a typical AMF production plant.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The manufacturing process of anhydrous milk fat (AMF) products requires the use of a number of process units. Of these process units, heat exchangers are utilised to transfer heat to a process stream (liquid stream such as cream stream or a heavy phase stream (rich in water and oil-in-water emulsion) or a light phase stream (oil rich)). In such heat exchangers the processing temperatures and conditions provided by the constant supply of a food source (such as the constituents of the cream or cream-derived components) allow bacteria to enjoy and flourish in a favourable growth environment.

The growth of bacteria (such as thermophiles) as a biofilm or clusters of bacteria growth within the heat exchanger is undesirable. Growth of this sort can impact upon the efficiency of heat transfer and/or fluid transfer through the heat exchanger (i.e. physical fouling of the process unit) - such fouling eventually impacts to such an extent that the process unit must be taken out of service and cleaned (such as via a clean-in-place operation, referred to as CIP within the industry). Bacterial growths are also unwanted as these may impact upon the sterility and level of quality of the product being processed through such a process unit. Once physical fouling of the process unit impacts upon the efficiency of the process unit and/or contamination levels of bacteria in a product stream from growth in the process unit reach unacceptable levels, the unit must be taken out of service and cleaned. Such cleaning usually means that there is down-time in the processes capability of the plant. The run-time of process units is shortened by such fouling and bacterial growth. Short run times result in a greater number of cleaning operations, resulting in a longer period of time to process a set quantity of product.

Most undesirable is contamination of a food / product stream with bacteria infection or reduced quality of that food / product stream by an increase to unacceptable levels of bacteria contained therein. As bacteria grows in the process unit/heat exchanger the biofilm bacterial cultures may develop to an extent that the bacteria begins to reduced the quality of the food stream. Once conditions in the process unit/heat exchanger such as these are reached the unit/exchanger must be removed from service and cleaned.

Any system which enables the run-times of a processing plant to be lengthened is advantageous. There are significant advantages associated with longer process runtimes for processing plants. Furthermore, an inexpensive system which is able to be readily integrated within existing AMF production plants will further contribute to significant advantages of incorporating the present invention into an AMF production facility.

For example, a typical AMF plant run-time is at present (in New Zealand) approximately 9 hours of production time. At the end of every 9 hours of product the plant must be taken off-line and CIP carried out on process equipment. CIP in the typical AMF plants in New Zealand at the present time may take approximately 3 hours. This means that there is a maximum production of 18 hours/day, with the remainder 6 hours being CIP time and production down-time.

It is hypothesised that the present invention will enable a single 9 hour run-time production plant to extend out to a single 21 hour run-time. This means that there is one less CIP operation per day, on average approximately 3 hours less time spent cleaning.

Therefore, using the figures above, for a production plant of the same capacity, extending the run-time from two 9 hour period and two 3 hour CIP periods to a single 21 hour runtime and a single 3 hour CIP period there would be a 16.7% increase in daily production capacity. Significant cost and material savings are also likely to result from reduced total water, electricity and steam costs. Increased process stability and enhanced control of process equipment may also result due to longer run-times. The costs of CIP will also be reduced, perhaps by as much as up to 50% due to reduction (in the case of a 21 hour run time) in the CIP operations required. Reductions in the manufacturing cost of product can be translated directly to increased profit margins.

Advantageously, the present invention relates to a method of inhibiting and/or disrupting bacterial and/or biofilm and/or thermophile growth within a process unit by thermal cycling of the temperature of the unit. In one embodiment of the present invention the process unit is a heat exchanger. The heat exchanger can be either of a plate-type or shell- and tube-type configuration. The heat exchanger can be operated in a co-flow or counter-flow manner. In the embodiments described below counter-flow plate heat exchangers are preferably utilised. For example, a heat exchanger supplied from GEA, model: EcoFlex NT 50 may be most suitable as the first heat exchanger, and a heat exchanger supplied from GEA, model: EcoFlex NT 50 may be most suitable as the second heat exchanger.

It is anticipated that a cream feed stream of between typically 35% to 50% fat/oil content is to be supplied for a typical AMF manufacturing plant.

With reference to the accompanying process flow diagram figures, a second embodiment of the present invention may broadly consist in a method for inhibiting and/or disrupting bacterial and/or biofilm and/or thermophile growth in a heat exchanger, the heat exchanger comprising a part of a system (1) for manufacture of anhydrous milk fat (hereinafter "AMF") comprising the steps of providing a feed stream of cream (2) from a cream balance tank (CBT) to a first heat exchanger (HX1) and elevating the cream stream temperature from an input temperature to an output temperature. The cream with the elevated temperature is then fed to a first separator (SEP1) and substantially separated into a light phase stream (LP1) and a heavy phase stream (HP1). The light phase stream (LP1) is then fed to a first balance tank (BT1) after which the light phase stream (LP1) is further processed, for example by feeding the light phase stream (LP1) to a second separator (SEP2) to affect a further separation of the light phase stream.

After a predetermined period of time of operating the process and, more particularly, the first heat exchanger (HX1), the first heat exchanger (HX1) is subjected to a thermal cycle treatment. The thermal cycle treatment comprises recycling at least a portion of the cream feed stream from the cream balance tank (CBT) about the first heat exchanger (HX1). In this manner, the first heat exchanger (HX1) no longer processes fresh cream feed and operates with a recycled stream of cream recycling about the first heat exchanger (HXt). As a result, the temperature of the heat exchanger (HX1) is caused to be elevated to a thermal cycling temperature and increases to temperatures above the operational temperature profile when processing a fresh cream stream. The temperature of the first heat exchanger (HX1) is changed by either a step change in temperature or by a more gradual elevation in temperature. The increased temperature of the heat exchanger during this recycle stream phase is maintained for a predetermined period of time.

In a separate part of an AMF plant, a further heat exchanger may independently be placed into a recycle mode such that the temperature of the heat exchanger is elevated sufficiently to disrupt and/or inhibit bacterial growth. According to this third embodiment of the present invention the method comprises a heat exchanger which comprises a part of a system for manufacture of anhydrous milk fat (hereinafter "AMF"). Such a method comprising the steps of providing a feed stream of cream from a cream balance tank (CBT) to a first heat exchanger (HX1) and elevating the cream stream temperature from an input temperature to an output temperature. The input temperature of the cream feed stream (2) (when not in a thermal cycle or recycle mode) is likely to be in the range of between substantially 6°C to substantially 10ºC. The output temperature of the cream stream (i.e. the elevated cream stream temperature after passing through the heat exchanger during "normal" processing or operational conditions) is likely to be in the range of substantially 55°C to substantially 6OºC. The oil (fat) concentration in the cream stream is typically around 40%, but may be a stream having an oil (fat) content of within the range of 35% to 50%.

The cream with the elevated temperature is then fed to a first separator (SEP1), also known as a cream concentrator, and substantially separated (concentrated) into a light phase stream (LP1) and a heavy phase stream (HP1). The light phase stream (LP1) may preferably be an oil (fat) rich stream of approximately 75%-78% concentration.

The light phase stream (LP1) is then fed to the first balance tank (BT1) after which the light phase stream (LP1) is further processed, for example by feeding the light phase stream (LP1) to a second separator (SEP2) to affect a further separation of the light phase stream. The light phase stream (LP1) fed to a second separator (SEP2) is separated into a light phase (an oil rich phase) stream (LP2) and a heavy phase (an emulsion rich phase) stream (HP2). The heavy phase stream (HP2) can then be fed to a second balance tank (BT2). The heavy phase stream (HP2) is then sent to and separated in a third separator (SEP3) to yield yet a further light phase stream (LP3) and a heavy phase stream (HP3). From this, the heavy phase stream (HP3) can be fed through a second heat exchanger (HX2) (and heated/cooled) prior to storage or further processing. Alternatively, the heavy phase stream (HP2) from the second separator (SEP2) is fed to the second balance tank (BT2) and subsequently passed through the second heat exchanger (HX2) for heating and/or cooling prior to storage or further processing. Heating/cooling is carried out to typically achieve a product outlet temperature from the heat exchanger of approximately less than 1OºC.

Bearing in mind the third embodiment described above, after a predetermined period of operation the second heat exchanger (HX2) is subjected to a thermal cycle treatment. The thermal cycle treatment comprises recycling at least a portion of the stream (HP2, HP3, HP5, LP3) which is fed to the second balance tank (BT2) about the second heat exchanger (HX2) and elevating the temperature of the second heat exchanger (HX2) to a thermal cycling temperature above an operational temperature. In doing so, the temperature of the second heat exchanger (HX2) is elevated, ideally to temperatures sufficiently above conditions suitable for bacterial growth or at least to temperatures sufficient to disrupt and/or inhibit bacterial / thermophile growth. The temperature elevation of the heat exchanger is maintained in this manner for a predetermined period of time. After the predetermined period of time, the recycling of the cream feed stream (2) about the first heat exchanger and the feed streams to the second balance tank (BT2) (HP2, HP3, HP5, LP3) are discontinued and the heat exchanger switches back to "normal" operational or processing conditions. "Normal" processing or operational conditions are considered to be the flow rates and temperatures associated with operation of the heat exchanger(s) during non-thermal cycling periods.

In a fourth embodiment, the present invention may broadly consist in a method for inhibiting and/or disrupting bacterial and/or biofilm and/or thermophile growth in a heat exchanger or exchangers, the heat exchanger(s) comprising a part of a system for manufacture of anhydrous milk fat (hereinafter "AMF") comprising the steps of providing a feed stream of cream from a cream balance tank (CBT) to a first heat exchanger (HX1) and elevating the cream stream temperature from an input temperature to an output temperature. The elevated temperature cream is then fed to a first separator (SEP1) and substantially separated into a light phase stream (LP1) and a heavy phase stream (HP1). The light phase stream (LP1) is fed to a first balance tank (BT1). Ideally the flow into the first balance tank (BT1) is greater than the flow out of the tank to subsequent processing operations. In this manner LP1 material is allowed to accumulate in the first balance tank (BT1). The input and output temperatures of the cream stream through the first heat exchanger have been discussed in previous embodiments.

The light phase stream (LP1) is further fed to a second separator (SEP2) and separated into a light phase stream (LP2) and a heavy phase stream (HP2). The heavy phase stream (HP2) is fed to a second balance tank (BT2). It is preferred that the flow into the second balance tank (BT2) is not more than the flow out of the tank during operational or processing operations. This prevents build up of material in the second balance tank (BT2). However, during a thermal cycling or recycle period of the second heat exchanger, the second balance tank (BT2) can be used to accumulate material being fed to it. In this manner, upstream processing is enabled to continue.

In one alternative, the material fed to the second balance tank (BT2) is to a third separator (SEP3). This third separator (SEP3) yields a light phase stream (LP3) and a heavy phase stream (HP3). The heavy phase stream (HP3) is further processed by passing through a second heat exchanger (HX2) for heating and/or cooling purposes prior to storage or for subsequent processing operations. In a second alternative, the heavy phase stream (HP2) discharged from the second separator (SEP2) is fed directly to the second balance tank (BT2) and material which is fed to the second balance tank (BT2) is subsequently fed through the second heat exchanger (HX2) for heating and/or cooling purposes prior to storage or further processing.

With reference to Figure 2, regions A and B illustrate the portions of an AMF manufacturing plant to which the present invention may be applied. More particularly, Figures 3 and 4 illustrate in more detail an embodiment of the present when applied to regions A and B, respectively.

With reference to Figures 3 and 4, Figure 3 illustrates one embodiment of the present invention of the recycle stream (RS) flow when the first heat exchange (HX1) is in a thermal cycling or recycle mode. The recycle stream (RS) in Figure 3 comprises a recycled stream of feed cream (2). Figure 4 likewise illustrates one embodiment of the present invention of the recycle stream (RS) flow when the second heat exchanger (HX2) is in a thermal cycling or recycle mode. Figure 4 additionally illustrates an additional recycled stream (RS1) which may form a part of the recycle stream (RS). The RS1 stream comprises the light phase stream from the third separator (SEP3), such a stream being LP3. The recycle stream (RS) in Figure 4 may therefore comprise a combination of streams HP2, HP3, HP5 and optionally LP3.

In a preferred embodiment, the second heat exchanger as described above cools the product passing through it to temperatures manageable for storage or subsequent processing. Such temperatures have been described above in previous embodiments.

Bearing in mind the above, after a predetermined period of operation the first heat exchanger (HX1) and the second heat exchanger (HX2) are each subjected to a thermal cycle treatment. The thermal cycle treatment comprising recycling at least a portion of the cream feed stream from the cream balance tank (CBT) about the first heat exchanger (HX1) and recycling at least a portion of the second balance tank stream (HP2, HP3, HP5, LP3) about the second heat exchanger (HX2). In this recycle mode the temperatures of the heat exchangers are elevated, as mentioned previously, preferably to temperatures sufficiently above or outside of the conditions which bacteria which may be growing within the heat exchangers may find favorable. Preferably, the elevated temperature is sufficient to disrupt or inhibit the growth characteristics of any bacteria growing within the heat exchanger. Such a thermal cycling of the first and the second heat exchangers (HX1 , HX2) is maintained for a predetermined period of time.

The ability to accumulate material in the first (BT1) can be achieved by running the first separator (SEP1) at higher throughput rates than the second separator (SEP2). For example, when a set point of a "high" level of material has accumulated in the first balance tank (BTI)there may then be sufficient material accumulated to allow the downstream processes to continue operating whilst the first heat exchanger (HX1 )is placed into a thermal cycle mode. The first balance tank (BT1)is advantageously provided with sufficient accumulation of material or volume of material which allows a continuous forward feed flow of material to further separation devices and/or subsequent processing units. As mentioned earlier, the heat exchangers are held in a recycle or thermal cycling mode for a length of time and at a thermal cycling temperature which is either sufficient to inhibit or disrupt the growth characteristics of the bacteria in the exchangers. Ideally, the balance tanks are sufficiently sized and/or the feed forward flow is of a sufficient flow rate to enable thermal cycling for sufficient time without the first balance tank (BT1) being emptied. In this manner, preferably the cream feed stream is operated in a semi-batch mode.

It is preferred that the periodic recycling of streams does not significantly reduce the AMF process plant capacity as the downstream processing rate is maintained by provision of sufficient material supplied from the accumulation in the first balance tank (BT1) during operational conditions.

Furthermore, it is anticipated that should the thermal cycling time for the heat exchangers be greater than the time available from relying upon time to empty the material which has accumulated in the first balance tank (BT1), then downstream processes of the AMF production plant can be placed into temporary recycle modes. In doing this, the material of the AMF production plant will simply recycle about various parts of the process and each part of the AMF process is prevented from running "dry". That is, no part of the process would run out of material to be processed. As a result of such downstream recycle processes, thermal cycling would not be limited to the capacity of the first balance tank (BT1). An advantage of this mode of operation is also that thermal cycling of the heat exchangers does not need to be dependent upon the level of accumulated material the first balance tank (BT1). Such downstream recycling would likely result in slight reduction in the average process capacity of the AMF plant during a total production run.

In addition, advantages of the present invention are provided in the energy efficiencies of effectively pre-heating the cream stream feed during the recycle or thermal cycle mode of operating the first heat exchanger (HX1). This allows a temporary reduction in the amount of additional heat requirements for imparting energy to the cream feed stream prior to feeding forward to the first separator (SEP1). Also, the cream balance tank (CBT) would preferably be operated so that the volume of cream residing within the cream balance tank (CBT) immediately prior to a thermal cycle is minimised or run to a low level. In this manner the amount of feed cream needing to be heated to an elevated temperature to effect the thermal cycling is kept to a minimum. Once the period of thermal cycling is finished, the cream feed source may once again continue to input cream into the cream balance tank (CBT) to ensure a cream feed stream (2) is provided to the first heat exchanger (HX1). Advantageously, an oversized first balance tank (BT1) volume as well as control of the flow rates of downstream processes would allow downstream processes from the first balance tank (BT1) to operate on a continuous basis.

Operating the cream feed stream on a non-continuous basis preferably allows for a continuous downstream process due to the use of balance tanks. At the same time, the use of such balance tanks allows the thermal cycling of the heat exchangers to at least go some way towards inhibiting and/or disrupting the growth of unwanted cultures, such as bacteria, within the heat exchanger.

Furthermore, it may be preferred that the thermal cycling temperature is independent of the operational temperature. This means that the thermal cycling temperature can be raised to temperatures higher than the operational temperatures to effect disruption and/or inhibition of the growth of bacterial cultures. Additionally, when thermal cycling temperatures are elevated to sufficiently high temperatures to effect bacterial growth inhibition/disruption the efficacy of the thermal cycling can be increased. Because of this increased efficacy of operating at higher temperatures on the inhibition/disruption of bacterial cultures, the period of time required for the thermal cycling treatment can be reduced, or the periods of operational processing between thermal cycling periods can be extended - further increasing the operational efficiency and run-times of an AMF plant. Finally, control of the growth of bacterial cultures/biofilms/thermophiles by implementing such a thermal cycling treatment leads to improved quality of the food stream (cream and dairy derived products) being processed in such a plant. This may all lead to advantageous cost implications.

According to the above process, and in conjunction with the accompanying figures, the process streams referred to above may be defined as having approximate or desired compositions of the following:

Examples of suitable separators can include:

SEP1 : Manufacturer: Westfalia Separator AG, model: MSE 350-01-777 SEP2: Manufacturer: Westfalia Separator AG, model: RSE 150-01-776 SEP3: Manufacturer: Westfalia Separator AG, model: MSE 55-01 -177 SEP4: Manufacturer: Westfalia Separator AG, model: MSE 100-01-177 SEP5: Manufacturer: Westfalia Separator AG, model: RSE 110-01-776 Examples of suitable heat exchangers can include: HX1 : Manufacturer: GEΞA, model: EcoFlex NT 50; or

Manufacturer: APV, model: N35-RKS16 HX2: Manufacturer: GEΞA, model: EcoFlex NT 50; or

Manufacturer: APV, model: H17-RKS16 HX3: Manufacturer: GEA, model: EcoFlex NT 50; or

Manufacturer: APV, model: N35-RKS16

Example 1 :

In one example of a typical AMF production facility incorporating the thermal cycling of heat exchangers as described above, theoretical process flow rates may be as follows:

Cream concentrator (i.e. SEP1) maximum feed flow: 18 m³/hr

Maximum light phase stream (LP1) flow to first balance tank (BT1): 10.8 m³/hr

Maximum flow of LP1 to third separator (SEP3): 9 m³/hr

Rate of first balance tank (BT1) LP1 material accumulation: 1.8 m³/hr

In the above calculations, if the first balance tank (BT1) has a maximum working volume of 1.4 m³ (1400 litres) and a low working volume of 0.2 m³ (200 litres), then the available change is 1.2 m³ (1200 litres).

On this basis:

Time to fill BT1 : (1.2m³/ 1.8m³) * 60 mins = 40 minute filling cycle.

Time to empty BT1 to low working volume: (1.2m³/ 9m³) * 60 mins = 8 minutes emptying cycle when in recycle mode

A simplified process flow of a typical AMF production plant facility is illustrated in Figure 5. Below is tabulated a theoretical mass balance around such a typical AMF production plant facility.

AMF product from plant: 6000 kg/hr

Cream capacity with 40% BF: 1 5 1 30 kg/hr α-serum stream or secondary skim from plant with 0.3% BF: 7195 kg/hr β-serum stream or buttermilk from plant with 1.5% BF: 1903 kg/hr Wash water from plant with 0.3% BF: 608 kg/hr Water evaporation losses: 24.10 kg/hr

Oil ex plant 6000.00 kg/h

Fat content in Oil 99.95 %

Cream fat content 40.00 %

Cream fat content ex.

Concentrator 76.00 %

Skim fat content ex. Concentrator 0.80 %

Homo effect 90.00 %

Cream fat content ex. Skimmer 25.00 %

Skim fat content ex. Skimmer 0.30 %

Oil ex Oil concentrator 99.50 %

Wash water 10.00 %

Oil ex. Polisher 99.60 %

Fat content in Wash water 0.30 %

Buttermilk fat content 1.50 %

Cream fat content ex. β-serum separator 65.00 %

MASS BALANCE

Oil flow ex Plant 6000.00 kg/h

Cream flow to Plant 15129.84 kg/h

Flow to Cream concentrator 15278.50 kg/h

Fat content to Cream concentrator 39.85 %

Flow ex Cream concentrator 7934.67 kg/h

Skim flow to Skimmer 7343.83 kg/h Skim milk flow ex Plant 7195.17 kg/h Cream flow at Skimmer 148.66 kg/h Flow to Oil concentrator 8963.01 kg/h

Fat content to Oil concentrator 74.74 %

Oil flow ex Oil concentrator 6031.97 kg/h

Fat content in Serum 22.80 %

Flow to Buttermilk skimmer 2931.04 kg/h

Cream flow ex Buttermilk skimmer 1028.34 kg/h

Serum ex Buttermilk separator 1902.70 kg/h

Flow to Polisher 6631.97 kg/h

Wash water flow to Polisher 600.00 kg/h

Fat content to Polisher 90.50 %

Oil flow ex Polisher 6024.10 kg/h

Wash water ex Polisher 607.87 kg/h

Water evaporation 24.10 kg/h

In a further example of a typical AMF production plant, according to the process flow diagram of Figure 1 , when run for a total of an 18 hour processing period, Tables 1-4 below exemplify the typical mass balance around such a system.

The foregoing description of the invention includes preferred forms thereof. Modifications may be made thereto without departing from the scope of the invention.

Claims

WHAT WE CLAIM IS:

1. A method of inhibiting and/or disrupting bacterial and/or biofilm and/or thermophile growth within at least one process unit by thermal cycling of the temperature of the unit.

2. A method for inhibiting and/or disrupting bacterial and/or biofilm and/or thermophile growth in at least one process unit, the at least one process unit comprising and/or incorporated in a part of a system for manufacture of anhydrous milk fat the method comprising the steps of: a. providing a feed stream of cream from a cream source to a first process unit of the at least one process units and elevating the cream stream temperature, b. feeding at least a portion of the elevated temperature cream stream to a first separator and substantially separating the elevated temperature cream stream into a first light phase stream and a first heavy phase stream, c. accumulating at least a portion of the first light phase stream, such that, after a predetermined period of operation, the first process unit is subjected to a thermal cycle treatment.

3. The method of claim 2 wherein the thermal cycle treatment comprises recycling at least a portion of the feed stream of cream fed to the first process unit from the cream source about the first process unit and elevating the operational temperature of the first process unit to a thermal cycling temperature and maintaining the thermal cycle treatment for a predetermined period of time.

4. A method for inhibiting and/or disrupting bacterial and/or biofilm and/or thermophile growth in at least one process unit, the at least one process unit comprising and/or incorporated in a part of a system for manufacture of anhydrous milk fat, the method comprising the steps of: a. providing a feed stream of cream from a cream source to a first process unit and elevating the cream stream temperature, b. feeding at least a portion of the elevated temperature cream stream to a first separator and substantially separating the feed stream of cream into a first light phase stream and a first heavy phase stream, c. feeding at least a portion of the first light phase stream to a second separator to separate the first light phase stream into a second light phase, stream and a second heavy phase stream, d. accumulating at least a portion of the second heavy phase stream, and either: e. carrying out a separation of the second heavy phase stream in a third separator to yield a third light phase stream and a third heavy phase stream and passing the third heavy phase stream through a second process unit, or f. passing the at least a portion of the accumulated second heavy phase stream through a second process unit, such that, after a predetermined period of operation the second process unit is subjected to a thermal cycle treatment.

5. The method according to claim 4 wherein the thermal cycle treatment comprises recycling at least a portion of the second heavy phase stream about the second process unit and elevating the operational temperature of the second process unit to a thermal cycling temperature and maintaining the thermal cycle treatment for a predetermined period of time.

6. The method of claim 2, further comprising the steps of: a. feeding at least a portion of the first light phase stream to a second separator to substantially separate the first light phase stream into a second light phase stream and a second heavy phase stream, b. accumulating at least a portion of the second heavy phase stream, and then either: i. carrying out a separation of the second heavy phase stream in a third separator yielding a third light phase stream and a third heavy phase stream and passing the third heavy phase stream through a second process unit of the at least one process units, or ii. passing at least a portion of the second heavy phase stream through a second process uint, such that, after a predetermined period of operation the first and second process units are each subjected to a thermal cycle treatment.

7. The method of claim 6 wherein the thermal cycle treatment comprises recycling at least a portion of the feed stream of cream fed to the first process unit and recycling at least a portion of the second or third, as applicable, heavy phase stream fed to the second process unit about the second process unit, and elevating the temperature of the first and the second process units from their respective operational temperatures to a thermal cycling temperature and maintaining the thermal cycle treatment for a predetermined period of time.

8. The method of any one of claims 2, 3, 6 or 7 comprising the step of: c. feeding at least a portion of the first light phase stream to a first balance tank.

9. The method of any one of the claims 4 to 7 or claim 8 when dependent on claim 6 or claim 7, comprising: feeding at least a portion of the second heavy phase stream to a second balance tank.

10. The method of any one of claims 2 to 9 wherein at least a portion of the first light phase stream is used to feed downstream process operations.

11. The method of any one of claims 2 to 10, wherein during a recycle mode or thermal cycling mode of operation, the feed stream of cream fed to the first process unit from the cream source is reduced to a minimum flow rate or flow is stopped completely.

12. The method of claim 3 or claim 7, wherein when the first process unit is in a thermal cycling mode, the feed cream stream which is recycling about the first process unit is heated in the first process unit.

13. The method of claim 5, wherein the second process unit heats the heavy phase stream being recycled thereto when in a thermal cycling mode.

14. The method of any one of the preceding claims wherein the or each process unit comprises a heat exchanger.

15. The method of claim 14 wherein the heat exchanger comprises a plate-type and/or shell- and tube-type configuration.

16. The method of claim 14 or claim 15 comprising operating the heat exchanger in a co- flow and/or counter-flow manner.

17. The method of any one of the preceding claims wherein the at least one process unit processes at least one liquid stream.

18. The method of claim 17 wherein the at least one liquid stream comprises dairy-derived material.

19. The method of claim 18 wherein the dairy-derived material comprises cream.

20. The method of any one of claims 17 to 19 wherein the at least one heat exchanger is fed by two liquid food streams, one being provided on the heating side of the exchanger and the other on the cooling side of the exchanger.

21. The method of any one of the preceding claims wherein the thermal cycling comprises increasing the operational temperature of the respective process unit for a predetermined period of time.

22. The method of claim 21 wherein the increase in temperature of the process unit is effected by recycling at least one stream through the process unit.

23. The method of claim 22 wherein during recycling or thermal cycling mode the at least one recycled stream is additionally heated by heating means.

24. The method of any one of claims 21 to 23 wherein the predetermined period of thermal cycling is between from substantially 20 seconds to substantially 45 minutes.

25. The method of claim 24 wherein the predetermined period of thermal cycling is in the range of from substantially 30 seconds to substantially 30 minutes.

26. The method of claim 25 wherein the predetermined period of thermal cycling is in the range of from substantially 1 minute to substantially 15 minutes.

27. The method of claim 26 wherein the predetermined period of thermal cycling is in the range of from substantially 2 minutes to substantially 10 minutes.

28. The method of claim 26 wherein the predetermined period of thermal cycling is in the range of from substantially 2 minutes to substantially 5 minutes.

29. The method of any one of the preceding claims wherein the period of thermal cycling takes place after a period of operational processing.

30. The method of claim 29 wherein the period of operational processing is in the range of from substantially 5 minutes to 4 hours.

31. The method of claim 30 wherein the period of operational processing is in the range of from 10 minutes to substantially 3 hours.

32. The method of claim 31 wherein the period of operational processing is in the range of from substantially 15 minutes to substantially 120 minutes.

33. The method of claim 32 wherein the period of operational processing is in the range of from substantially 25 minutes to substantially 90 minutes,

34. The method of claim 33 wherein the period of operational processing is in the range in the range of from substantially 45 minutes to substantially 60 minutes.

35. The method of any one of the preceding claims wherein the thermal cycling is undertaken such that the respective process unit temperature is elevated to a thermal cycling temperature which is sufficient to disrupt and/or inhibit bacterial and/or biofilm and/or thermophile growths/multiplication of at least some bacteria and/or biofilms and/or thermophile types which may grow within the respective process unit.

36. The method of any one of the preceding claims wherein the thermal cycling is undertaken at elevated temperatures above the processing or operational temperatures.

37. The method of claim 36 wherein the elevated temperature is between substantially 50°C to 100°C.

38. The method of claim 36 wherein the thermal cycling is undertaken at elevated thermal cycling temperatures of between substantially 55°C to substantially 90ºC.

39. The method of claim 36 wherein the thermal cycling is undertaken at elevated thermal cycling temperatures in the range of from between substantially 60ºC to substantially 80ºC.

40. The method of claim 8 or 9 or any one of claims 10, 11 or 14 to 39 when dependent on claim 8 or claim 9 wherein in the periods of operational processing the input feed rate to the respective balance tank is greater than the output flow rate.

41. The method of claim 8 or claim 9 or any one of claims 10, 11 or 14 to 40 when dependent on claim 8 or claim 9 wherein the period of thermal cycling is determined or limited by the time taken for a low level volume in the corresponding balance tank to be reached and/or for the corresponding balance tank to substantially empty and/or for the quantity of material held within the corresponding balance tank to be reduced to a set point.

42. The method of claim 41 wherein in the event that a minimum level of material in the corresponding balance tank is reached, output therefrom is inhibited and/or reduced and/or at least one stream is recycled thereto.

43. The method of claim 41 or claim 42 wherein when the low tank level is reached the thermal cycling of the corresponding process unit is stopped and/or the corresponding feed cream stream supplied thereto.

44. The method of any one of claims 2 to 43 wherein the respective stream is heated in the process unit to an output temperature of not more than substantially 8OºC during operational processing.

45. The method of claim 44 wherein the output temperature is not more than substantially 75ºC during operational processing.

46. The method of claim 45 wherein the output temperature is not more than substantially 65ºC during operational processing.

47. The method of claim 47 wherein the output temperature is in the range of between substantially 55°C to substantially 65ºC during operational processing.

48. The method of any one of claims 2, 13 or 40 to 47 or any one of claims 14 to 39 when dependent on any one of claims 2 to 13 wherein the heavy phase stream discharged from the first separator to a fourth separator to yield a heavy phase stream and a fourth light phase stream.

49. The method of claim 48 wherein the fourth heavy phase stream is a buttermilk or an α- serum stream or a precursor thereof.

50. The method of any one of claims 4 to 7 or any one of claims 8 to 49 when dependent thereon wherein the second heavy phase stream discharged from the second separator is a buttermilk or an β-serum stream, or a precursor thereof.

51. The method of any one of claims 4 to 7 or any one of claims 8 to 49 when dependent thereon, or claim 50 wherein the second light phase stream is discharged from the second separator to a fifth separator.

52. The method of claim 51 wherein the fifth separator comprises a vacuum system or flash separator.

53. The method of claim 51 or claim 52 wherein the fifth separator dischargers a fifth light phase stream comprising a butteroil.

54. The method of any one of claims 51 to 53 wherein the fifth separator discharges a fifth heavy phase stream for use in addition to or instead of the second heavy phase stream.

55. The method of any one of claims 4 to 7 or any one of claims 8 to 54 when dependent on any one of claims 4 to 7 wherein the third heavy phase stream is processed through the second process unit to yield a buttermilk or β-serum stream, or a precursor thereof.

56. The method of any one of claims 2 to 55 wherein a phase inverter or a homogeniser phase inverts or homogenises the first light phase stream.

57. The method of any one of claims 51 to 55 or claim 56 when dependent on any one of claims 51 to 55, wherein a heat exchanger elevates or controls the temperature of the second light phase stream to a set point temperature prior to feeding the second light phase stream to the fifth separator.

58. The method of any one of the preceding claims wherein thermal cycling takes place substantially at heat transfer surfaces within the respective process unit.

59. The method of claim 58 wherein the heat transfer surfaces within the process unit are those surfaces in direct contact with any or all of the following: the cream stream, the light phase stream(s) or the heavy phase stream(s).

60. The method of any one of the preceding claims wherein the or each process unit comprises external heating means or cooling means.

61. The method of any one of the preceding claims wherein the or each process unit has two sources of feed.

62. The method of claim 61 wherein one source is fed to a portion of the unit requiring heating and the other source is fed to a portion of the unit requiring cooling.

63. The method of claim 62 wherein during thermal cycling of the unit, the feed of the source providing cooling to the unit is minimised or stopped or at least reduced.

64. The method of claim 48 or claim 49 wherein the fourth heavy phase stream is fed to the first process unit to provide heat so as to pre-heat the cream feed stream during operational conditions.

65. The method of claim 48, 49 or 64 wherein during recycle mode or thermal cycling mode feed of the fourth heavy phase stream from the fourth separator is minimised or halted.

66. The method of any one of the preceding claims wherein the method is incorporated into a system of manufacturing anhydrous milk fat.

67. A method of inhibiting and/or disrupting bacterial and/or biofilm and/or thermophile growth within a process unit substantially as herein described with reference to any one of the embodiments showing Figures 1 to 4.

68. A system for inhibiting and/or disrupting bacterial and/or biofilm and/or thermophile growth within a process unit by thermal cycling of the temperature of the unit.

69. A system for inhibiting and/or disrupting bacterial and/or biofilm and/or thermophile growth in a process unit, the process unit comprising or incorporated in a part of a system for manufacture of anhydrous milk fat, the system comprising means for implementing the method of any one of claims 1 to 67.