WO2010045686A1

WO2010045686A1 - Cleaning method

Info

Publication number: WO2010045686A1
Application number: PCT/AU2009/001391
Authority: WO
Inventors: Duncan Bell
Original assignee: Orica Australia Pty Ltd
Priority date: 2008-10-24
Filing date: 2009-10-23
Publication date: 2010-04-29
Also published as: AU2009307047A1; NZ592484A

Abstract

The invention provides an in-place cleaning (CIP) method for food and/or beverage processing equipment, such as milk processing equipment, fouled with a foulant such as milk fouling. The method comprises the steps of treating the foulant with an acidic solution to remove metal ions from the foulant and basifying the acidic solution thereby contacting the treated foulant with a basic solution to remove at least some of the treated foulant. The acidic solution and/or the basic solution comprise at least one chelant in an amount sufficient to stabilise metal ions in the basic solution following the pH inversion.

Description

CLEANING METHOD

FIELD OF THE INVENTION

The present invention relates to cleaning fouled food and/or beverage processing equipment. In one embodiment the invention relates to a method of cleaning milk processing equipment in situ. For convenience only, the background of the invention will be discussed in terms of cleaning milk processing equipment.

BACKGROUND OF THE INVENTION

Over time foulant can build up in food and/or beverage processing equipment and it is generally necessary to clean the equipment on a daily basis. In milk plants, the foulants typically include proteinaceous material such as milk proteins as well as minerals (including metal ions), fats, carbohydrates and micro-organisms. Due to the size and shape of the equipment, it can be difficult to remove foulant from the equipment, because it is impractical for mechanical scrubbing to be employed. For example, the fouled surfaces may be the inside surfaces of pipes and/or enclosed tanks which might include therein membrane filters, plate heat exchangers and other components necessary for the processing of food or beverages e.g. separators. In most cases, therefore, it is necessary to clean the equipment without moving it i.e. to clean the equipment in situ or in place. Accordingly, milk processing equipment is generally cleaned daily using one or more cleaning solutions fed into and circulated through the pipes or sprayed by spray-ball jets into tanks, without the use of mechanical scrubbing. When a cleaning solution is used in situ in this way, the heat exchanger usually used to heat the processed product, e.g. milk, can be employed to heat the cleaning solution.

Traditional Cleaning-In-Place (CIP) procedures for removing foulant from milk processing equipment involve ceasing production, flushing the equipment with water, circulating an alkali solution, flushing the equipment with water, circulating an acid solution and flushing the equipment with water again. This may be followed by other steps, such as a sanitiser step to reduce bacterial loading. The alkali solution generally comprises caustic soda, and the acidic solution is generally a nitric acid or nitric/phosphoric acid blend. Nevertheless, even using this traditional CIP procedure, foulant can still build up over time. When foulant builds up beyond a tolerable level it is sometimes necessary to employ a different, more rigorous cleaning procedure. The tolerable level could be any level pre-determined by, for example, internal or industry standards, or any level that affects the ability of the processing equipment to properly process the food and/or beverage.

One different cleaning procedure that has been employed when foulant builds up beyond a tolerable level involves circulating an acidic solution comprising sulfamic acid in the processing equipment before overdosing the sulfamic acid solution with an alkali solution. This process is referred to as an Acid-Override process. Once the sulfamic Acid-Override process has been completed, it is necessary to further clean the processing equipment with an acid wash to solubilise mineral compounds precipitated on the surfaces of the equipment as scum following inversion of the acidic pH to an alkaline pH.

Sulfamic acid is provided in powder form and presents a significant manual handling hazard as well as being relatively expensive. Furthermore, sulfamic acid and its byproducts are corrosive to stainless steel, which is a material used to form the processing equipment, so the sulfamic acid procedure cannot be used frequently and is typically only employed once every few weeks. A further disadvantage of the treatment with sulfamic acid is that it can result in large pieces of foulant coming free from the internal sides of the equipment, which can make cleaning more difficult, particularly if these pieces lodge on the internal filters inside the equipment. In light of these disadvantages, the sulfamic acid procedure cannot be employed as a daily or otherwise frequent regime.

There exists a need for an effective procedure to clean fouled processing equipment that reduces and preferably prevents the build up of foulant beyond a tolerable level. Preferably, this process is one which can be applied regularly, i.e. daily. The time required to clean processing equipment is a factor, so any daily procedure should be at least as efficient, and preferably more efficient, than the current CIP regime. Time is a factor because any time required to clean the equipment is less time that can be employed to process the product. Such a procedure developed for use in a milk processing plant could be applied, where possible, to clean other food and/or beverage processing equipment.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides an in place cleaning method for food and/or beverage processing equipment fouled with a foulant, the method comprising the steps of: (a) treating the foulant with an acidic solution to remove metal ions from the foulant; and (b) basifying the acidic solution thereby contacting the treated foulant with a basic solution to remove at least some of the treated foulant; wherein the acidic solution and/or the basic solution comprise at least one chelant in an amount sufficient to stabilise metal ions in the basic solution.

The present method provides an improved cleaning-in-place (CIP) method which, in some embodiments, results in the removal of foulant (sometimes referred to as soil) more quickly than the traditional CIP procedure undertaken on the equipment cleaned. The method can be used instead of the traditional CIP procedure whenever the traditional CIP procedure would have been employed, for example, mid-run and/or end of a processing run (EOR). The step of first treating the foulant by contacting it with the acidic solution is thought to produce a demineralised or "treated foulant" having some or all of the metal ions removed from it. The treated foulant, having a decreased metal ion content, is more porous, less viscous and less adhered to the surface of the food and/or beverage processing equipment. This is believed to improve the ability of the basic solution to remove at least some of the treated foulant from the equipment.

The metal ions in the foulant come from the mineral content of the food and/or beverage that was processed in the equipment. For example, non-fat solids in milk include ions of calcium, phosphate, magnesium, potassium, sodium, zinc, chloride, iron, copper. Other compounds which can be removed by the acidic solution in addition to metal ions include, for example, carbonates, bicarbonates, citrate, etc. - A -

It is believed that while some protein hydrolysis of the foulant may occur when the foulant is contacted with the acidic solution, most of the hydrolysis occurs when the treated foulant is contacted with the basic solution. However, while the metal ions removed are stable in the acidic solution (i.e. they do not precipitate), they are less stable in the basic solution and therefore have a tendency to precipitate as the pH swings from the acid pH to the basic pH. For example, when cleaning milk processing equipment, calcium phosphate can precipitate upon inversion of the pH. Precipitation can reduce the effectiveness of the action of the basic solution in removing treated foulant and also results in scumming of the processing equipment surfaces, which requires further cleaning steps. In order to reduce the amount of precipitation of metal ions as the pH increases, the acidic and/or the basic solution comprise at least one chelant. The chelant is present in an amount sufficient to stabilise at least some and preferably all of the metal ions leached by the acid as the pH of the solution is inverted to a basic pH. The stabilisation prevents or at least reduces the scumming of the processing equipment following cleaning. This obviates or at least reduces the need for a further acid wash step after the cleaning has been undertaken.

There may be more than one chelant present in solution. Advantageously, the at least one chelant is added with the acid concentrate used to form the acidic solution, so the metal ions leached into solution have already been sequestered by the chelant when the acidic solution is basifϊed. Alternatively, the chelant can be added separately prior to the acidic solution, or it can be added to the acidic solution in the processing equipment. Alternatively or in addition, the chelant can be added with the base concentrate used to form the basic solution to stabilise the metal ions already sequestered.

The chelant(s) should be chosen to be stable and soluble in the acid and base solutions used. Subject to this, at least one of the chelants present can advantageously be selected from a phosphonate, gluconic acid, ethylene diamine tetraacetic acid (EDTA), nitriloacetic acid (NTA), diethylenetriaminepentaacetic acid (DTPA), methylglycinediacetic acid (MGDA), glutamic acid diacetic acid (GLDA), phosphanobutane tricarboxylic acid (PBTC), amino trimethylene phosphonic acid (ATMP) or salts thereof and combinations thereof. In a preferred embodiment, the chelant is a combination of sodium gluconate and amino trimethylene phosphonic acid (ATMP).

The chelant can be acidic and, in a preferred embodiment, the chelant contributes to the acidity of the acidic solution. The chelant should also be able to maintain or exhibit chelating properties following inversion of the pH.

The chelant can be present in the acid concentrate and/or the base solution concentrate in a range of from about 0.1 % w/w to about 20 % w/w, in some embodiments about 0.5 % w/w to about 10 % w/w and in other embodiments about 1 % w/w to about 2 % w/w. If the chelant is added separately an equivalent concentration or amount can be used.

The amount of chelant required will differ depending upon the type of chelant used i.e. how many metal centres the chelant can bind with, the ratio of the surface area of fouled equipment to volume of cleaning solution and the thickness and type of that foulant on the surface. For example, a mineral-rich foulant will require more chelant than a foulant comprised mainly of fats. In a preferred embodiment, the acidic solution contains a sufficient amount of chelant to stabilise the foulant in solution. The amount of chelant that will be required can be determined based on prior calculations and/or it can be estimated by the skilled addressee based on the teaching of the present specification and in the light of prior experience with the process equipment.

In some embodiments, the base concentrate comprises a proportion of the required chelant, which when added to the acidic solution provides the total amount of required chelant. Thus, if the total amount of required chelant is about 20 % w/w, about 10 % w/w could be provided in the acidic solution and about 10 % w/w could be provided in the base concentrate, or combinations of a similar nature provided the total chelant composition equals about 2 % w/w.

In some embodiments, it is preferable to sequester or bind 100 % of the metal ions in the basic solution following inversion of the solution pH and this will be achieved if sufficient chelant with respect to metal ions is provided. However, depending on the nature of the foulant, only a percentage, e.g. at least 95 % or at least 90 % of the metal ions in the basic solution may require sequestration following inversion of the solution pH to avoid or at least reduce scumming of the processing equipment. In other embodiments, only a percentage e.g. 80 % of the metal ions present will need be sequestered following pH inversion because the remaining e.g. 20 % may be incapable of precipitating as scum. This could be determined based on trial and error, and where this is the case, an amount of chelant suitable to sequester the required percentage of metal ions could be used in either or both of the acid and basic solutions. Using the method of the present invention there may be no scumming observed. However, some scumming could perhaps be tolerated depending upon the use to which the processing equipment is directed.

The chelant may advantageously be used together with a dispersant to ensure that removed foulant is unable (or has a decreased ability) to deposit as scum following pH inversion. Examples of dispersants that are suitable for use include maleic/acrylic copolymers, or homopolymers and copolymers of maleic acid and an olefin. Dispersants can be added with the acid solution or added during the acid stage or with the basic concentrate or during the alkali stage of the treatment. Dispersants can also be used in conjunction with any stage leading up to the final flush. The use of dispersants is particularly useful when there is a high foulant load, such as for evaporators.

The process according to the present invention can solubilise mineral components including metal ions, and allow large amounts of protein and fat foulant to be released, unsolubilised, in a short period of time. This is to be contrasted with traditional CIP processes which typically release the foulant slowly and under conditions that allows proteins and fats to solubilise. For this reason, it can be important when cleaning some types of equipment, for example equipment containing separators and other components prone to blockage for a dispersant to be incorporated into the cleaning solution to ensure that fatty and/or proteinaceous foulant does not redeposit on the cleaned surfaces.

It may also be important for the unsolubilised protein/fat foulant to be physically removed from the recirculating cleaning solution, as this will reduce the potential for redeposition or blocking of the process equipment. Separators can achieve the removal of solids by periodically opening small ports in the outer edge which, due to the centrifugal action of the separator, expels any solids that have accumulated. The timing, frequency and duration of the ports opening can be altered to suit particular process and cleaning requirements. Since the process of the present invention is significantly different from traditional CIP processes, it may be necessary to alter the normal opening of the ports, a process known as desludging, to best remove any unsolubilised material and avoid redeposition or blockage. For other processes, it may be necessary to strategically open drain valves to expel excessive foulant during cleaning.

The step of basifying the acidic solution can comprise adding a base concentrate directly into the acidic solution at a sufficient concentration to provide the cleaning solution with a basic pH. In some embodiments, the pH of the acidic solution is basified to be in the range of from about 8 to about 14. In one advantageous embodiment, the pH is adjusted to be in the range of from about 11 to about 14.

The acid solution can comprise one or more inorganic acids, and/or one or more organic acids. Organic acids are advantageous because they are often present in the food and/or beverage that is processed in the equipment being cleaned. For example, in one embodiment, the acidic solution comprises lactic acid which is an acid found naturally in milk. The acid or combination of acids may be selected depending upon, for example, the price and availability of the acid, its ability to form soluble salts (e.g. in the milk industry its ability to form soluble calcium salts) and/or the desired waste water nutrient profile. It is also possible to choose a combination of acid and base that will produce a salt in situ which may be useful in the cleaning process, for example a sanitiser. It is known that sodium lactate acts as a sanitiser. Accordingly if lactic acid is chosen as the acid component and sodium hydroxide chosen as the base it is possible to generate sodium lactate in situ. It is envisaged that sufficient sodium lactate could be generated to have a sanitiser function, thereby reducing bacterial loading in the equipment. The acidic solution is advantageously non-corrosive to the material(s) from which the pipe-work and other components of the food and/or beverage processing equipment are made under the normal cleaning conditions (i.e. the normal cleaning times, concentrations and temperatures). By "non-corrosive", it is meant that the materials are not significantly broken-down by chemical reactions with the acidic solution such that the cleaning process can be used regularly, e.g. daily. It is common for components of food and/or beverage processing equipment to be made from stainless steel and to have rubber seals between some connections. The acidic solution should be one which does not corrode the stainless steel or rubber by a general and uniform removal of material, i.e. by dissolution.

The non-corrosive nature of the acidic solution means that the cleaning process can be used regularly, for example daily, to clean food and/or beverage processing equipment. The regular and effective cleaning regime may reduce the periodic need for alternative cleaning regimes or products.

The pH of the acidic solution that contacts the foulant is advantageously less than 5.5. This increases the likelihood that any calcium trapped in the foulant is removed by the acidic cleaning solution. Preferably, the pH of the acidic cleaning solution circulated in the processing equipment is in the range of from about 1.0 to 5.0. In one advantageous embodiment, the pH of the acidic cleaning solution during use is in the range of from about 1.5 to about 3.5.

The food and/or beverage processing equipment is cleaned in situ. Advantageously, the cleaning solutions pass through the equipment along the same route as that taken by the food or beverage that was processed. This should ensure all fouled surfaces are contacted and cleaned. When the equipment is in use, the food or beverage flows through the pipework and fouling may build up on the internal walls of the pipes or collect on any internal filters or other obstacles therein. In tanks, the foulant may build up on the bottom surface or walls and/or on any impellers or other components used in the tank during processing. In the milk industry, the method can be used to remove foulant from heat exchangers, in particular plate heat exchangers (PHE) which have a large surface area. The PHE can be in series with centrifugal separators used to separate milk into its components. The method can also be used to remove foulant from the separator plates or discs, the separator bowls and any spindles therein.

By "cleaning" or "clean" it is meant that at least some of the foulant is removed from the food and/or beverage processing equipment. The equipment is cleaned "in place" or in situ, which means the components of the processing equipment are not removed from the position they are usually in during normal processing of the food and/or beverage. When the equipment includes pipes and/or vessels such as tanks, cleaning in place may be the only option, or the preferred option, when the alternative is dismantling the processing equipment to gain access to the fouled surfaces.

In some circumstances the process of the present invention can be used in conjunction with a traditional CIP cleaning process, for example by alternating between the process of the invention and a traditional CIP process.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention and other embodiments will now be described with reference to the following drawings, which are intended to be exemplary only, and in which:

Figure 1 is a graph showing the results of cleaning a fouled stainless steel disc;

Figure 2 is a graph showing data obtained from a traditional CIP procedure undertaken on milk processing equipment;

Figure 3 is a graph showing data obtained from a process undertaken in accordance with an embodiment of the present invention on the same milk processing equipment as for Figure 2; and

Figure 4 is a graph of the foulant (soil) turbidity profile from the same process graphed in Figure 3.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION The method of the invention can be used to remove at least some foulant from any type of food and/or beverage processing equipment. For example, the food and/or beverage processing equipment could be for processing red meat, seafood or poultry, fruit and/or vegetables, dairy products, juice, carbonated beverages, alcoholic beverages, confectionary, rice and/or pasta, cereal and/or bread. In particular, the method could be applied to remove at least some foulant from beer and/or wine processing equipment, cheese processing equipment, milk processing equipment, yoghurt processing equipment and/or cream processing equipment. The method is advantageously employed to clean milk fouling from components of a milk processing plant. Embodiments of the invention will be described with particular reference to milk processing equipment, but it is not so limited.

In milk processing equipment, the foulant is likely to include proteinaceous material such as milk proteins, e.g. casein and whey, as well as fats, carbohydrates, minerals (including metal ions) and micro-organisms.

It is believed that most foulants, including milk fouling, form on a surface by first forming a compact sub-layer composed of mineral components and protein. This sub layer provides protuberances to which large protein aggregates may become anchored. β-Lactoglobulin, one example of these large proteins, partially denatures at about 70 ⁰C, a temperature employed during most milk processing. As the protein denatures, disulfide groups are exposed that facilitate bridging between different denatured molecules. The interaction between molecules results in the formation of large polymerised and insoluble protein aggregates, which also bind to the precipitated minerals, creating a porous, spongy foulant.

A traditional CIP method comprises the following steps:

1. Pre-flush the processing equipment with a water to displace residual product; 2. Flush remaining product residue to drain;

3. Add aqueous solution to the processing equipment and increase the temperature of the aqueous solution;

4. Basify the aqueous solution and contact the foulant with the basic solution; 5. Drain the basic solution from the processing equipment;

6. Flush the basic solution from the equipment with water;

7. Add aqueous solution to the processing equipment and increase the temperature of the aqueous solution;

8. Acidify the aqueous solution and contact the foulant with the acidic solution; 9. Drain the aqueous solution from the processing equipment; and

10. Post-flush the processing equipment.

This traditional CIP process can take between 15 minutes and 4 hours depending upon the size of the equipment being cleaned, for example, the length of the pipe-work and/or the size of any silos or tanks.

In the method of the present invention, the foulant is contacted with an acidic solution before being contacted with a basic solution. In one embodiment, the method according to the invention comprises the following steps:

1. Pre-flush the processing equipment with water to displace product;

2. Flush remaining product residue to drain;

3. Add aqueous solution to the processing equipment and increase the temperature of the aqueous solution; 4. Acidify the aqueous solution with an acid concentrate (plus chelants) to provide an acidic solution and contact the foulant with the acidic solution;

5. Basify the acidic solution by addition of a base concentrate to provide a basic solution (plus chelants) and contact the foulant with the basic solution;

6. Drain the processing equipment; and 7. Post-flush the processing equipment. The process of the present invention provides a faster rate of foulant removal compared with the traditional CIP process. The present process can reduce the cleaning time by about 25 % to 50 %. For example, if the traditional CIP process takes 2 hours 30 minutes, the present process could reduce the time to about 1 hour 15 minutes. This faster rate of foulant removal allows shorter overall cleaning times to be employed to clean the processing equipment.

As outlined above, the pH inversion from the acidic solution to basic solution has an effect on the solubility of the metal ions taken up into the acidic solution. Chelant present in the acidic solution bind to the metal ions or otherwise disperse them in solution to especially increase their solubility and to prevent or at least reduce their tendency to precipitate as the solution pH increases. Alternatively, or in addition, chelant present in the basic solution can stabilise the sequestered metal ions to prevent or at least reduce precipitation at the basic pH. The total amount of chelant provided in either or both of the acidic and basic solutions is sufficient to sequester at least some of the metal ions leached during the acid treatment step. The amount of chelant required will depend upon the type of chelant as well as the nature and amount of foulant present.

It is preferable to select a chelant that is phosphorus and nitrogen free, so the waste-water from the process will be free of these elements. In one preferred embodiment, therefore, the chelant includes sodium gluconate. This will reduce the nutrient profile of the effluent and thereby reduce environmental problems associated with disposal of the treated wastewater.

Advantageously, the chelant allows the cleaning process to be undertaken without the need for an acid wash step afterwards to remove scum, which is beneficial to industry in the form of cost and time savings.

However, other steps can be taken if necessary, for example if there is a need to sanitise the equipment with a sanitiser a sanitisation step can be undertaken. Examples of sanitisers which may be suitable for this purpose include peroxyacetic acid (a premixed combination of peroxide and acetic acid) and or other combinations of peroxide with organic acids including citric and lactic acid. It may also be possible to use sodium lactate, which could potentially be generated in situ by reacting lactic acid with sodium hydroxide.

The foulant in the food and/or beverage processing equipment may be contacted with the acidic solution by acidifying an aqueous solution that is in the processing equipment. A concentrated acid could be added to the aqueous solution (to thereby dilute it), or the acidic solution at the desired concentration could be added to displace the aqueous solution. The acidic solution may be an aqueous solution at a concentration of about 0.01 % w/w to about 10 % w/w, in some embodiments about 0.05 % w/w to about 7.5 % w/w, and in other embodiments about 0.1 % w/w to about 5 % w/w.

The acidic solution may also comprise one or more surfactants which can improve the wettability of the foulant. The surfactant should be stable in the acidic solution and also preferably stable in the basic solution. The surfactants used may be anionic, non-ionic, cationic or amphoteric.

Suitable nonionic surfactants that may be used include branched alcohol alkoxylates or end capped alcohol alkoxylates. For example, alkoxylated substituted alcohols which comprise ethylene oxide and optionally propylene oxide and/or butylene oxide. The alkoxylated alcohols can comprise the ethylene oxide, propylene oxide and butylene oxide units in the form of blocks or in random distribution.

The Plurafac LF are also suitable surfactants, particularly the end-capped Plurafac LF grades. Plurafac LF types are low foaming nonionic surfactants which consist of alkoxylated, predominantly unbranched fatty alcohols which contain the higher alkene oxides alongside ethylene oxide. The end-capped Plurafac grades remain stable even in contact with highly concentrated alkali hydroxides, and their antifoam properties are retained. Thus they are ideal antifoaming agents for highly alkaline cleaners and also as additives for alkaline cleaning processes. Other suitable nonionic surfactants include, for example, alkoxylated C8- to C22-alcohols, such as fatty alcohol alkoxylates or oxo alcohol alkoxylates. Examples of suitable nonionic surfactants are also alkylamine alkoxylates or alkylamide ethoxylates and alkylphenol ethoxylates.

A further class of suitable nonionic surfactants may be alkyl polyglucosides with 8 to 22, preferably 10 to 18, carbon atoms in the alkyl chain. These compounds mostly contain 1 to 20 glucoside units. Another class of useful nonionic surfactants may be N- alkylglucamides.

Suitable anionic surfactants may be fatty alcohol sulfates, e.g. lauryl sulfate, cetyl sulfate, myristyl sulfate, palmityl sulfate, stearyl sulfate or tallow fatty alcohol sulfates. Other suitable anionic surfactants include olefinsulfonates and disulfonates, which can also represent mixtures of alkene- and hydroxyalkanesulfonates or -disulfonates, alkyl ester sulfonates, sulfonated polycarboxylic acids, alkyl glycerol sulfonates, fatty acid glycerol ester sulfonates, alkylphenol polyglycol ether sulfates, paraffinsulfonates having about 20 to 50 carbon atoms (based on paraffin obtained from natural sources or paraffin mixtures), alkyl phosphates, acyl isothionates, acyl taurates, acyl methyltaurates, alkylsuccinic acids, alkenylsuccinic acids or monoesters or monoamides thereof, alkylsulfosuccinic acids or amides thereof, mono- and diesters of sulfosuccinic acids, acyl sarcosinates, sulfated alkyl polyglycosides, alkyl polyglycol carboxylates, and hydroxyalkyl sarcosinates.

The anionic surfactants may be added in the form of salts. Suitable salts include alkali metal salts, such as sodium, potassium and lithium and ammonium salts, such as e.g. hydroxethylammonium, di(hydroxyethyl)ammonium and tri(hydroxyethyl)ammonium salts.

Typical examples of amphoteric surfactants may be alkylbetaines, alkylamidobetaines, aminopropionates, aminoglycinates or amphoteric imidazolium compounds. Examples include cocoamphocarboxypropionate, cocoamidocarboxypropionic acid, cocoamphocarboxyglycinate and cocoamphoacetate. Suitable cationic surfactants may be substituted or unsubstituted, straight-chain or branched quaternary ammonium salts, for example C8- to C16-dialkyldimethylammonium halides, dialkoxydimethylammonium halides or imidazolinium salts with a long-chain alkyl radical.

As mentioned above, the acidic solution may also comprise a dispersant. The acidic solution may also further comprise one or more defoamers, which reduce foam production in the equipment and thereby improve cleaning efficiency. One suitable defoamer is an EO/PO block co-polymer. Within each series of block copolymer products, defoaming performance increases as ethylene oxide content decreases and molecular weight increases. The PLURONIC® surfactants are widely used as defoamers and are suitable for use in the present process. The reverse-structure PLURONIC® R surfactants can also be used and are effective in protein-soil defoaming and other defoaming applications.

In one embodiment, the acid concentrate comprises acid in a range of from about 10 % w/w to about 80 % w/w, preferably 20 % w/w to about 60 % w/w; a surfactant in a range of from about 5 to about 15 % w/w; a defoamer in a range of from about 5 to about 15 % w/w and a chelant in a range of from about 1.0 to about 10.0 % w/w with the balance being water.

Advantageously, the pH of the acidic solution is in the range of from about 1.5 to about 3.5 when first added to the processing equipment. If concentrated acid is added directly to an aqueous solution circulating in the equipment, the strength and amount of the concentrated acid added can be calculated to result in an aqueous acidic solution having a pH of from about 1.5 to about 3.5. It is believed that a pH of about 1.5 to about 3.5 assists in demineralising e.g. calcium from the foulant, and may assist in optimally removing other metal ions.

The acidic solution should remain in contact with the foulant for a period of time sufficient to remove at least some metal ions from the foulant thereby providing a treated foulant. This will depend upon the size of the processing equipment, i.e. the amount of time it takes for the cleaning solution to undertake a circuit or lap around the equipment which will depend upon the length of the pipe-work. It is believed that passing the solution through the equipment for 1 to 3 cycles will be sufficient time for acid treatment to occur. However, depending upon the nature and amount of foulant, more or less contact time may be required. This can be determined by the skilled addressee by trial and error. Where the cleaning solution is sprayed into tanks in the equipment, the length of time the spray is in use should be sufficient to allow the acid to remove at least some metal ions from the foulant and this will depend upon the size of the tank.

The acidic solution may consist essentially of an organic acid or an inorganic acid or a combination of the two may be used, any of which solutions can be aqueous. The inorganic acid may be any inorganic acid that is non-corrosive under the cleaning conditions. The acid can be known for use in cleaning food and/or beverage processing equipment. For example, the inorganic acid could include hydrochloric acid, nitric acid, phosphoric acid, sulphuric acid, phosphorous acid, sulphurous acid, or combinations thereof. Preferably, a non-phosphorus and non-nitrogen containing acid is selected to reduce the amount of phosphorus and nitrogen released in the waste-water.

The organic acid may comprise straight chain or branched carboxylic acids including lactic acid, acetic acid, formic acid, ascorbic acid, hydroxymaleic acid, methane sulphonic acid, mandelic acid, glycolic acid, salicylic acid, a pyranosidyl acid such as glucuronic acid or galacturonic acid, citric acid, maleic acid, acrylic acid, tartaric acid, pamoic acid, alginic acid, gentisic acid or lactobionic acid or combinations thereof. In one advantageous embodiment used to clean milk processing plant, the organic acid is lactic acid.

After contacting the foulant in the food and/or beverage processing equipment with an acidic solution, the acidic solution is basified without an interim drain or rinse. This is achieved by treating the acidic solution, which is in contact with the foulant, with a concentrated basic solution. The amount of the concentrated base added should be sufficient to cause a pH swing from acid pH (i.e. pH in the range of 1.5 to 3.5) to a basic pH i.e. to a pH in the range of from about 8 to about 14. In one embodiment, the alkaline pH range is from about 11 to about 14. In some embodiments, the acidic solution is basified by gradually adding concentrated base over a period of time e.g. 5 minutes. The acidic solution is advantageously basified at a speed that ensures that the alkali is thoroughly mixed over the acid and that there are no slugs of either acid or base in the cleaning circuit. This can be predetermined and/or controlled by a Programmable Logic Controller (PLC).

The basic solution is as an aqueous solution at a concentration of about 0.01 % w/w to about 10 % w/w, preferably about 0.05 % w/w to about 7.5 % w/w, and more preferably

0.1 % w/w to 5 % w/w. The basic solution may comprise an alkali metal hydroxide, an alkaline earth hydroxide, a carbonate, a silicate or electrically activated water or any combination thereof. The alkali metal hydroxide could include lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, aluminium hydroxide or calcium hydroxide or combinations thereof. In one embodiment, the basic solution comprises a combination of sodium hydroxide and potassium hydroxide. In a further embodiment, the basic solution comprises only sodium hydroxide.

The basic solution may also comprise one or more surfactants and/or one or more defoamers as described above with respect to the acid solution. The basic solution may also include a dispersant as described above. However, in one embodiment a base concentrate suitable for use in the process comprises base in a range of from about 40 % w/w to about 99 % w/w, preferably, about 90 % w/w to about 99 % w/w and chelant in a range of from about 0.1 to about 10 % w/w with the balance being water.

The basic solution should remain in contact with the foulant for a period of time sufficient to remove at least some of the treated foulant. As described above in relation to the acidic solution, this period of time required will depend upon the size of the processing equipment (i.e. the period of time it takes for the cleaning solution to undergo a lap) and the nature of the foulant. About 1 to 3 laps will be sufficient contact time in most cases, although the skilled addressee will determine this by past experience or trial and error. Some processing equipment includes components that require additional time in contact with the acid and/or basic cleaning solutions, or that require an operation to be undertaken to cause either or both of the cleaning solutions to fully contact the surfaces of that component (i.e. a component may need to be flooded with the cleaning solution to promote contact with the foulant). For example, milk processing equipment includes separators having separator discs that may require flooding with the cleaning solution (particularly the acidic cleaning solution) in order to properly remove foulant. It may also be necessary to open outlet ports or drain valves to release liquid containing sludge or foulant. Such steps, including desludging steps, are also undertaken in the traditional CIP procedure for the same reasons.

The foulant is advantageously contacted with the acidic and/or basic solutions at an elevated temperature i.e. above room temperature. The elevated temperature may assist in denaturing proteinaceous material in the fouling and/or may allow more rapid removal of at least some of the foulant. The temperature of the cleaning solution (i.e. the acidic solution and the basic solution) is advantageously increased to above the temperature at which any protein in the foulant denatures. The acidic and/or basic solutions may be used in the temperature range of from about 30 °C to about 80 °C, in some embodiments 60 °C to 80 °C. In one embodiment, the optimum cleaning temperature is at or about 70 ⁰C. Higher or lower temperatures could be employed, but the cleaning may not be as efficient. If the temperature deviates from the optimum cleaning temperature (which can be predetermined) the foulant may require additional contact time with the cleaning solution and/or mechanical action may be required to improve cleaning and/or the chemical strength of the cleaning solution may need to be increased.

The temperature of the cleaning solution can be increased by heating the solution using the heating means present in the processing equipment. Optionally, a dedicated cleaning solution heat exchanger could be provided. Alternatively, or in addition, the acidic and/or the basic solution could be heated prior to being passed into the equipment, but it should be understood that there would be undesirable heat loss during transfer. Preferably, the minimum concentration of acid and base required to remove foulant is used to clean the food and/or beverage processing equipment. Using a smaller concentration of acid and base reduces costs in terms of the amount of the reagents used, and also reduces waste disposal costs.

It is desirable to remove about 100 % of foulant from the equipment. However, removal of at least about 80 %, or at least about 90 % of the foulant may be acceptable under some circumstances. The amount of foulant left behind following a cleaning process will affect the subsequent processing of the food and/or beverage. For example, foulant retards heat transfer, so any foulant remaining in the equipment will increase the energy required to increase the temperature of the product processed. Residual foulant also adversely affects the cooling efficiency of the equipment and can harbour bacterial growth.

Once the cleaning process of the invention has been undertaken, the food and/or beverage processing equipment cleaned is flushed with water (sometimes referred to as an intermediate rise or final rise) to ensure that any residual chemicals are removed to drain.

The step of basifying the acidic solution provides substantial cost savings through reducing the amount of water used and the time and energy required to perform the procedure. If the acidic solution were drained from the equipment, the time taken to undertake the process can be increased by about 10 to 20 % which is commercially undesirable. Rinsing the pipe-work prior to addition of base also results in more waste-water. If the foulant is to be contacted with the acidic and basic solutions at an elevated temperature, energy and time savings may result if the acidic solution is already at the desired temperature when the basification occurs.

For a better understanding of the invention and to show how it may be performed, embodiments thereof will now be described, by way of non-limiting examples only, with reference to the accompanying drawings. EXAMPLE 1

Fouling of stainless steel discs can be used as a model of the fouling that occurs on a dairy heat exchange surface. The fouling on a stainless steel disc may be weighed, photographed and observed. Moreover, procedures for removing the fouling on the disc may be tested and the rate of protein dissolution may be obtained.

Preparation of Fouled Stainless Steel Discs

A stainless steel disc was heated by oil to approximately 100 ⁰C. Warmed milk was then poured onto the disc and the disc allowed to foul over a one hour period. The disc was removed from the milk and rinsed in distilled water for 10 minutes. The disc was dried and weighed.

In general, discs fouled with approximately 0.2 g of milk foulant were used for experiments. A disc was considered acceptable if it weighed between 0.170 g to 0.240 g and was not fouled in patches. Procedures for removing the foulant from the disc were tested.

General Procedure to Remove the Foulant from the Disc

A fouled disc was immersed into a cleaning solution and spun at 64 rpm. Samples were taken from the cleaning solution every 30 seconds. The aqueous samples having foulant dissolved therein were measured using an ultra-violet(UV)/visible(Vis) spectrophotometer. An absorbance reading was taken at 280 nm. The absorbance at 280 nm is approximately proportional to the amount of protein foulant present in the solution.

Methanesulfonic acid (MSA) and Phosphoric acid

The fouled disc was immersed into an aqueous acidic cleaning solution. The aqueous acidic solution comprised 50 % v/v phosphoric acid (as an 80 % solution) and 3 % v/v methane sulphonic acid (MSA). The solution also included surfactants.

Given that the surface area of the disc is small compared with the volume of cleaning solution used, chelants were not used in this experimental set-up since the effects of scumming were insignificant. However, assuming the experimental procedure was scaled up to clean milk processing equipment fouled with an equivalent thickness of the same type of milk fouling, about 5 % (w/w) of sodium gluconate would be added to the acidic cleaning solution. If calculations or the results reveal that more chelant is required to sequester the mineral/metal ion content of the foulant, more chelant would be added to a subsequent similar cleaning process.

The disc was spun at 64 rpm at 70 °C. Samples were taken every 30 seconds. After 5 minutes, the disc was removed from the acidic solution. The acidic solution was basified by the addition of concentrated NaOH.

The disc was returned to the basified solution and spun at 64 rpm at 70 ⁰C. Samples were taken until the disc was clean.

Figure 1 depicts the data from three separate tests undertaken using the procedure of Example 1. In these three tests, each disc tested was approximately 20 % clean prior to basification, and was more than 95 % clean after a total of about 13 minutes.

EXAMPLE 2

Three cleaning processes were undertaken in accordance with embodiments of the present invention on a module in a Milk Treatment plant. The plant was run for at least 5.5 hours before cleaning. A traditional CIP process was also undertaken for comparison.

In each of the process trials in accordance with embodiments of the invention, the acid concentrate comprised:

78 % w/w lactic acid 1 % w/w Guerbert alcohol ethoxylate (surfactant) 1 % w/w EO/PO block co polymer (defoamer) 1.6 % w/w amino trimethylene phosphonic acid (ATMP) (chelant) balance water.

The acidic concentrate was used as an aqueous solution in an amount ranging from about 0.1 % w/w to about 5 % w/w. The solution was circulated at 70 +/- 10 ⁰C.

In each of the process trials, the basic concentrate comprised:

47 % w/w caustic soda 1.4 % w/w/ sodium gluconate (chelant) balance water

The basic concentrate was used as an aqueous solution in an amount ranging from about 0.1 % w/w to about 5 % w/w. The solution was circulated at 70 +/- 10 ⁰C.

Table 1 shows the data from a traditional CIP procedure undertaken on the milk processing equipment. Table 2 shows the data from the processes embodying the invention undertaken on the same milk processing equipment.

Table 1: results from a traditional CIP procedure

Table 2: results from three trial processes (1) to (3) embodying the process of the invention

When compared with the traditional CIP process, the trial processes achieved an average time saving of 34.5 minutes. There were no detrimental effects on micro and operating parameters during or after trials (1) to (3).

Samples were taken throughout each of the process trials (1) to (3) and during the traditional CIP process to gain an understanding of the type and profile of the foulant (soil) being released into solution. The samples were analysed for the following:

Chemical Oxygen Demand (COD) - measurement of organic loading Calcium (mg/kg) - measurement of mineral/metal ion loading Absorbance (280 nm) - measurement of protein loading

Figure 2 shows that during the traditional CIP cleaning process, the majority of calcium was removed during the acid treatment. There was minimal absorbance at 280 nm detected throughout the CIP, with the highest values during the caustic preflush. Most of the COD loading occurred during the start of the caustic preflush, as expected, and towards the end of the caustic recirculation. Figure 3 shows the results from process trial (2). The graph shows that high levels of calcium and a high COD were detected during the treatment of the foulant with the acidic solution. On addition of the basic solution, the absorbance increased indicating protein removal.

The optional additional acid step undertaken during trial (1) resulted in more calcium (about 20 mg/kg) being removed. The calcium levels present in the acid following the process of the invention are about half the residual compared to the standard CIP.

The foulant/soil (turbidity) profile shown by the graph of Figure 4 clearly demonstrates the magnitude of foulant release when base is added to the acid solution during process trial (2). This data is backed up by the data gained from laboratory analysis of the CIP samples.

EXAMPLE 3 The same cleaning process as described in Example 2 was undertaken on a plant used to process goat's milk. The cleaning processes were undertaken mid-run as well as end of run (EOR). A traditional CIP was also undertaken from comparison. The results are shown in the tables below.

Table 3: the time required for a traditional CIP procedure

Table 4 shows a set of trial results. Process trial (1) was undertaken end of run (EOR), with a traditional CIP undertaken mid-run Process trial (2) was undertaken mid-run and process trial (3) was undertaken at the end of the same run.

Table 4: results from four process trials (1) to (4) embodying the invention

Approximately 37 minutes of time was gained compared with the traditional CIP process. This time saving enables the feed-line and evaporator to be turned around efficiently.

Adenosine Tri-Phosphate (RLU) measurements were taken after the process trials to measure the level of microorganisms present in the plant. ATP levels below 150 RLU are deemed sanitary for dairy. The ATP swab results are as depicted in Table 4 below.

Table 5: ATP results from process trial (4)

The plant was visually and microbiologically clean.

For this equipment, the angle of the concentrate heater on the feedline could be altered to allow flow to run uphill slightly. This would ensure the pipe work is full all the time which may improve heat transfer and also the cleaning performance.

EXAMPLE 4

The process of the present invention can be used to clean processing equipment used in the brewing industry.

Some examples of in place cleaning methods that can be replaced by the CIP method of the present invention include Lauter Tun CIP, Kettle CIP, Whirlpool Separator CIP, Plate Heat Exchanger CIP, Fermenter CIP, Maturation CIP and Maltexo Evaporator CIP, etc.

A typical traditional CIP undertaken in the brewing industry comprises the following steps:

1. Pre-rinse;

2. Caustic circulation, typical concentration in a range of from about 1.5 to about 6.0 % w/w (Rezolv Super^{σM Orica)}) (60 minutes);

3. Intermediate rinse (10 minutes);

4. Acid circulation, typical concentration in a range of from aboutl.O to about 2.0 % w/w (Nitrobrite^{(TM Orica)}) (60 minutes);

5. Second intermediary rinse (25 minutes); 6. Sanitiser circulation, typical concentration in a range of from about 0.13 to about 0.5 % w/w (Perform⁰™ ^Orica)) (20 minutes).

The process of the present invention that could be applied to the equipment used in the brewing industry may comprise the following steps:

1. Pre-rinse; 2. Acid circulation including chelants, typical concentration in a range of from about 0.1 to about 5.0 % w/w acid (25 minutes);

3. Basification by alkali addition to existing acid step;

4. Alkali circulation including chelants, concentration in a range of from about 0.3 to about 2.0 % w/w alkali (40 minutes);

5. Final rinse, (25 minutes);

6. Sanitiser circulation, concentration in a range of from about 0.13 to about 0.5 % w/w (Perform^{(TM Orica)}) (20 minutes if required).

EXAMPLE 5 - formulations

The following acid and base concentrates can be used to prepare cleaning formulations suited to clean particular processing equipment. The acid and base components below are commercially available products containing commercially available concentrations of active ingredient. For example, lactic acid is available as an 88 % solution and sodium hydroxide is available as a 49-50 % solution.

Cleaning formulation - phosphate free

Acid concentrate 50 % w/w lactic acid

10 % w/w methylglycinediacetic acid (MGDA)

20 % w/w Polyacrylic acid

5 % w/w alcohol ethoyxlate

5 % w/w endcapped fatty alcohol ethoxylate balance water

Base concentrate 20 % w/w potassium hydroxide 40 % w/w sodium hydroxide 2 % w/ alkyl glucoside balance water

Cleaning formulation - fast action low foam

Acid concentrate 50 % w/w Methane Sulfonic acid 10 % w/w Phosphonic acid 20 % w/w Polyacrylic acid 5 % w/w alcohol ethoyxlate LF balance water Base concentrate 50 % w/w sodium hydroxide 5 % w/w sodium gluconate 2 % w/w alkyl glucoside

5 % w/w PO/EO block polymer

10 % w/w methylglycinediacetic acid (MGDA) balance water Cleaning formulation - sodium sensitive soil

Acid concentrate 50 % w/w lactic acid 20 % w/w polyacrylic acid 10 % w/w phosphonic acid 10 % w/w gluconic acid 5 % w/w alcohol ethoxylate 5 % w/w EO/PO block polymer

Zføse concentrate 50 % w/w potassium hydroxide 10 % w/w EDTA K4 chelant balance water

Cleaning formulation - high soil load Acid concentrate

50 % w/w Lactic acid

20 % w/w Polyacrylic acid

5 % w/w alcohol ethoyxlate LF

5% w/w Sulfonic acid balance water

Base concentrate 50 % w/w sodium hydroxide 5 % w/w sodium gluconate 10 % w/w methylglycinediacetic acid (MGDA) balance water

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the invention includes all such variations and modifications which fall within the spirit and scope. The invention also includes all of the steps, features, compositions and compounds referred to or indicated in this specification, individually or collectively, and any and all combinations of any two or more of said steps or features.

Claims

THE CLAIMS

1. An in place cleaning method for food and/or beverage processing equipment fouled with a foulant, the method comprising the steps of: (a) treating the foulant with an acidic solution to remove metal ions from the foulant; and

(b) basifying the acidic solution thereby contacting the treated foulant with a basic solution to remove at least some of the treated foulant; wherein the acidic solution and/or the basic solution comprise at least one chelant in an amount sufficient to stabilise metal ions in the basic solution.

2. The method according to claim 1, wherein the acidic and/or basic solutions further include a dispersant.

3. The method according to claim 1 or 2, wherein the at least one chelant is added with an acid concentrate used to provide the acidic solution.

4. The method according to any one of the preceding claims, wherein at least one of the chelants is selected from a phosphonate, gluconic acid, ethylene diamine tetraacetic acid (EDTA), nitriloacetic acid (NTA), diethylenetriaminepentaacetic acid (DTPA), methylglycinediacetic acid (MGDA), glutamic acid diacetic acid , (GLDA), amino trimethylene phosphonic acid (ATMP), phosphanbutane tricarboxylic acid (PBTC) or salts thereof and combinations thereof. In a preferred embodiment, the chelant is a combination of sodium gluconate and amino trimethylene phosphonic acid (ATMP).

5. The method according to any one of the preceding claims, wherein the acidic solution comprises one or more organic acids.

6. The method according to claim 5, wherein the organic acid is selected from glycolic acid, citric acid, lactic acid or methane sulphonic acid or any combination thereof.

7. The method according to claim 5, wherein the organic acid is lactic acid.

8. The method according to any one of the preceding claims, wherein the basic solution comprises an alkali metal hydroxide, an alkaline earth hydroxide or electrically activated water or any combination thereof.

9. The method according to any one of the preceding claims, wherein the temperature of the acidic solution is about 70 ⁰C.

10. The method according to any one of the preceding claims, wherein the temperature of the basic solution is about 70 °C.

11. The method according to any one of the preceding claims, wherein the acidic solution and/or the basic solution further include one or more surfactants.

12. The method according to any one of the preceding claims, wherein the acidic solution and/or the basic solution further include one or more defoamers.

13. The method according to any one of the preceding claims, wherein the foulant is milk fouling.

14. The method according to claim 13, wherein the food or beverage processing equipment cleaned is a component of a milk processing plant.

15. The method according to any one of claims 1 to 12, wherein the food or beverage processing equipment cleaned is a component of a beer processing plant

16. The method substantially as hereinbefore described with reference to the drawings and/or the examples.

17. Acid and/or base concentrate formulation for use in an in place cleaning method for food or beverage processing equipment substantially as hereinbefore described with reference to the drawings and/or the examples.