CIP Handbook v1

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Cleaning Handbook

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Docum ent owner Appr oved Release Date Issue Page

Cecilia Svensson Anders Göransson 2008-11-14 1 1 (83)

Cleaning

Handbook

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1. INTRODUCTION...4

1.1 CIP 1.1 CIP Validation Validation ProcedureProcedure ...5...5

1.2 Glossary & Definitions 1.2 Glossary & Definitions ...5...5

2. HYGIENIC DESIGN OF L INES AND COMPONENTS ...6

2.1 2.1 IntroductionIntroduction...6...6

2.2 Hygienic Design Prerequisites 2.2 Hygienic Design Prerequisites ...6...6

2.3 2.3 Hygienic Hygienic design...design...9...9

2.4 Hygienic Ris 2.4 Hygienic Risk Assessmentk Assessment ...25...25

2.5 Hygienic Design Checklist – Machines and Peripheral Equipment...26

2.6 Hygienic Design Checklist – Process Lines & Plants...27

3. CIP TECHNOLOGY ...29

3.1 Different 3.1 Different Types of Types of SoilSoil ...2929 3.2 Water Chemistry and Quality 3.2 Water Chemistry and Quality ...31...31

3.3 3.3 CIP TheoCIP Theoryry ...33...33

3.4 3.4 Detergent Detergent Chemistry...Chemistry...35...35

Alkalis ...36

Acids ...37

Surfactants (wetting agents)...37

Sequestering Agents (chelating agents) ...38

Oxidation Agents ...39

Overview of Some Cleaners and Disinfectants ...40

3.5 Deterg 3.5 Detergent Concentratient Concentrationon ...43...43

Dosing of Cleaning Agents...44

3.6 3.6 Cleaning Cleaning Temperature...Temperature...46...46

3.7 Cleaning 3.7 Cleaning TimeTime ...48...48

3.8 3.8 Cleaning Cleaning Flow...Flow...49...49

3.9 CIP Sequences 3.9 CIP Sequences for Certain for Certain Products...Products...57...57

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Aseptic Intermediate Cleaning...60

3.10 CIP of Specific Components in a Processing Line 3.10 CIP of Specific Components in a Processing Line ...61...61

Separators...61

Homogenisers ...61

Tank Cleaning...62

3.11 Contro 3.11 Control of l of Cleaning ResultCleaning Result...65...65

3.12 Disinfection/Sterilisation of Equipment...66

Sterilisation ...66

Disinfection...66

3.13 Guidelines for Determining Cleaning Intervals for Sterilisers...67

3.14 3.14 CIP CIP SystemsSystems ...68...68

Design of CIP Systems ...69

Centralised CIP ...70

FURTHER CIP READING...72

Appendix Appendix...73....73

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1. Introd uctio n

Cleaning, in this context, is the removal of deposited soil from processing equipment surfaces, and is an essential operation in food processing. The main reasons for cleaning are to satisfy food safety and regulatory standards, and to increase shelf-life and reduce spoilage rates. It is also compulsory for suppliers of food processing equipment to guarantee that the equipment can be cleaned. The purpose of cleaning is to ensure that processing equipment is physically clean, i.e. all visible soil is

removed.

The principle of cleaning is very easy: the forces that bind the soil to the surface of the equipment have to be overcome. This is achieved by mechanical and/or chemical effects, together with an increase in temperature. A term often used in cleaning is the Zinner circle, which defines the four main parameters governing the cleaning process: cleaning temperature, cleaning flow, detergent concentration and cleaning time. These are all closely related.

Designing and implementing cleaning procedures are both extremely important, but before all else – processing equipment must be designed for hygiene. It must be possible to clean the equipment. A badly designed valve or processing unit will

endanger good hygiene and can not be properly cleaned. Hygienic design is the basis for a good cleaning result, preventing the consumer’s health being put at risk due to hazards that can affect food safety and the quality of processed or packaged food.

The aim of this document is to provide guidelines in hygienic design when integrating process equipment into a process line, and to provide a general overview of the

importance of hygienic design. Furthermore, the document also describes the cleaning-in-place (CIP) state of the art. It briefly describes some of the different detergents used and the parameters of the Zinner circle. In the last section of Chapter 3 various CIP systems are described.

The target groups for this Cleaning Handbook are pre-project leaders, field service engineers, designers, process engineers, development engineers and staff from market companies. However, all those who need to know more about CIP should hopefully find this a useful introduction.

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1.1 CIP Valid atio n Proc edur e

A CIP validation procedure has been developed at Tetra Pak Processing Systems, which is owned by Tetra Pak Dairy & Beverage (document FCDPM 0706-001). The objective of this CIP validation procedure is to verify the effectiveness of the cleaning procedures in Tetra Pak’s processing equipment. The layout of the document is presented in Fig. 1. The following issues are discussed:

• Design qualification • In-house validation

• Installation qualification • Operational qualification and • Performance qualification

For a more detailed description the reader is referred to the CIP validation document. The document also describes a method of assessing cleanliness. It is based on a method of determining the value of ATP on the cleaned surface. A limit is suggested defining clean processing equipment.

Fig. 1.

Fig. 1. The five steps in the CIP validation procedure.

1.2 Glos sary & Definiti ons

The European Hygienic Engineering & Design Group (EHEDG) is an association working in the field of hygiene. They have developed a glossary including some of the most frequently used terms, phrases and expressions in cleaning and hygiene. The EHEDG Glossary is given in the appendix.

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2. Hygi enic De sig n of Lin es and Compo nents

2.1 Introduction

Within Europe, the essential requirements of the Machinery Directive, 98/37/EC, should be met in respect of both safety risks to the operator of the equipment and hygiene risks (Annex 1, paragraph 2.1) to the food (i.e., the product processed by the equipment). The hygienic requirements of the directive can be met by using the C-standard EN 1672-2:2005. The principles for performing a Hygienic Risk Assessment can also be also found in the same standard; see also Tetra Pak Corporate Standard B 2153.05.

Hygienic requirements in the USA are to be found in Food & Drug Administration legislation, FDA CFR Title 21 Food and Drugs, in the Grade “A” Pasteurized Milk Ordinance (PMO) and the USDA Guidelines for the Sanitary Fabrication of Dairy Equipment. Equipment exported to the USA must have a TPV approval according to the 3A-SSI standard. Lubricants must have an NSF class H1 approval.

Other countries have similar legislation, often corresponding to, or referring to, EU or US legislation and standards. However, questions concerning local legal demands and standards must be checked by each Tetra Pak market company.

2.2 Hygienic Design Prerequis ites

The single most important issue in engineering is to consider food safety, i.e. a hygienic design. A design method that eliminates risks to both hygiene and safety should be adopted. If this is not possible, then options safeguarding both hygiene and safety should be employed. If this is not possible, either hygiene or safety should be safeguarded. Where no design or safeguarding options to adequately control both hygiene and safety risks are possible on the engineering level, one of the risks, or both, must be dealt with by other safety measures, including instructions to the user.

The following affect the design and must be considered:;

- Type of product

- Materials in contact with food

- Utilities in contact with food

- Environment Type of product Type of product

The following are presented for guidance and as examples of the range and type of factors that must be considered regarding the process line and the

components/equipment in question when undertaking a risk assessment.

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equipment be used for a wide range of products in many industries (e.g. a pump)? Components are normally tested using water, or liquids with a similar viscosity. The component may therefore not be suitable for soups, sauces, or similar products.

b) The type of product to be processed by the equipment: Will the product be contaminated (e.g. a raw material), or will it be pasteurised or aseptic? Are additives used? A product recipe may call for additives such as starch or stabilisers, or others to increase the fat or protein content, etc. This can cause problems during cleaning and may affect the choice of components and the flow engineering, etc., and must also be considered.

c) The degree of further processing: Will the product processed by the equipment subsequently undergo a further process which acts as a hazard elimination step (e.g. heat treatment), or is the process for which the equipment is intended the final process? The method used for heat treatment, as well as the time/temperature

combination differs depending on the type of product and its properties: such as viscosity, homogeneity, content of fibres or particles, whole berries, etc.

d) Specific application of the product:

1. Is the product to be used by the consumer immediately after processing, or does the product have a shelf-life during which the food safety hazard could increase (e.g. microbial growth)? Use of hygienic zoning must be considered for ESL products, incubation areas, etc.

2. Will the product be used by a specific consumer group to whom the hazard may present a more serious risk (e.g. babies, the elderly or the infirm)? It may be necessary to fulfil specific demands, such as high quality welds,

differentiation of production lines due to allergens in a product, etc.

e) The degree of cleaning, disinfection, pasteurization, sterilization and/or inspection: Is the equipment to be cleaned, disinfected, pasteurized, sterilized and/or inspected after every batch, routinely during the day, every day, or every week, etc.?

f) The use of the equipment: Is the equipment likely to be well maintained or used infrequently? Is it designed for high or continuous use, and is misuse foreseeable? This will affect the use of aseptic and non-aseptic equipment, as well as necessary barriers such as steam, sterile air, nitrogen, etc.

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Materials in contact with food Materials in contact with food

The following are presented for guidance and as examples of the type of factors regarding materials in contact with food that must be considered for the process line and the components/equipment to be used in the various stages in risk assessment.

Under the intended conditions of use, the materials in contact with food shall be: • corrosion resistant

• non-toxic

• inert to the product, i.e. they must

-not absorb material (except when technically or functionally unavoidable)

-not transfer undesirable odours or colours, or taint the food;

-not contribute to the contamination of food, or have any adverse influence on the food.

Detailed legal demands and directives are enforced for plastic, rubber, ceramics, etc. within the EU and the USA, as well as in several other countries, such as Japan. Glass should be avoided in equipment that comes into contact with food, and if used it must be splinter free, and it must be impossible for it to get into the food product. When

necessary, filters are to be installed in the production line to avoid contamination from sacks, etc.

Lubricants used in food production equipment must be of Food Grade, NSF approved, class H1. In the USA 10 mg/l is allowed in the product and in the EU the product must contain no oil.

It is important to take into account the legal demands included in the design criteria in the purchase documentation sent to the suppliers.

Utilities in contact with food Utilities in contact with food

The following examples of utilities are presented for guidance and as examples of the type of factors that must be considered regarding the process line and the

components/equipment to be used.

Steam

Steam must be of a specific quality when used in contact with food. Culinary or clean steam must be used as steam normally contains additives to prevent calcium deposits in the steam-generating system. These additives are toxic and must not come into contact with food.

Water

Water must be of a special quality when used in contact with food. Potable water according to the WHO recommendation must be used. Furthermore, Tetra Pak places specific demands on water quality, for technical reasons, to ensure correct

functionality and to avoid corrosion of components/equipment. The water quality is naturally also of the utmost importance for the results of cleaning, for example, in avoiding re-contamination.

Compressed air

Compressed air must be of a specific quality: dry, clean and oil free, when used in contact with food, for example in ice cream freezers. Additional active carbon filters,

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or corresponding equipment must be used when compressed air is used as sterile air in aseptic applications.

Ventilation:

Ventilation: the flow, temperature and humidity of incoming air must be controlled. Zoning may have to be considered to avoid contamination being spread from a lower zone to a higher one. Special HEPA filters then have to be installed to remove particles.

It is important to address the legal demands included in the design criteria in the purchase documentation sent to the suppliers.

2.3 Hygienic design

General requirements General requirements

Materials must be suitable for the intended use. Surfaces of materials and coatings shall be durable and cleanable and, where required, capable of being disinfected, unflawed, resistant to cracking, chipping, flaking and abrasion, and undesirable matter must not be able to penetrate the surface under the intended use.

Surfaces Surfaces

1. The surface finish shall be suitable for the intended use.

2. Surfaces shall be cleanable and, where required, it must be possible to

disinfect them. For this purpose they must be smooth, unflawed or sealed. The surface design and finish shall be such that the product is prevented, as far as possible, from becoming accidentally separated from the food contact area

and from returning to it, if that return could cause a hazard associated with the processed food.

3. Surfaces shall have a finish such that no product particle can become trapped in small crevices, thus becoming difficult to dislodge and so introduce a contamination hazard.

The above requirements also apply to dismountable parts, which are removable for cleaning.

NOTE: Guidance for measurement of surface finish (roughness specification Rz and/or Ra) can be found in EN ISO 4288. Additional requirements for surface finish can be found in some equipment-specific type C

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Joints Joints

Permanent joints Permanent joints

Joints shall be sealed and hygienic. Recesses, gaps, crevices, protruding ledges, inside shoulders and dead spaces shall be avoided. If technically impossible, adequate design solutions (e.g. cleaning or disinfection instructions, etc.) are to be given.

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Dismountable joints Dismountable joints

Dismountable joints shall exhibit a true and hygienic fit. Gasket compression is to be limited by a mechanical stop.

Fasteners Fasteners

Fasteners such as screws, bolts, rivets, etc., shall be avoided. If technically

impossible, adequate solutions (e.g. cleaning or disinfection instructions, etc.) shall be given.

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Drainage Drainage

a) not drainable 1 concentric reducer 2 centric reducer

The equipment should preferably be self-draining; if this is not possible, it must be easy to remove the residual liquid by other means.

Note:

Note: In our applications piping should normally remain filled with water to prevent contamination and to avoid pitting corrosion which may occur when droplets evaporate.

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Internal angles and corners Internal angles and corners

Internal angles and corners shall be constructed such that they can be cleaned

effectively and, where required, can be disinfected. Internal angles and corners are to comply with the technical requirements given in equipment-specific C standards.

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Dead spaces Dead spaces

Dead spaces are to be avoided unless technically impossible in the design, construction or installation of the equipment. Unavoidable dead spaces shall be constructed in such a way that they are drainable/cleanable and can be disinfected, when required.

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Bearings and shaft entry points Bearings and shaft entry points

Bearings shall either be located outside the food area, except where this is technically unavoidable, or designed for and lubricated with food grade lubricant, cleanable and where required capable of being disinfected.

Shaft seals and moving shafts in the food area shall be self- (or product-) lubricated, or should be designed for and lubricated with food grade lubricant, cleanable and, where required, capable of being disinfected.

Note:

Note: Requirements for equipment used in aseptic processing can be found in specific C standards.

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Instrumentation and sampling devices Instrumentation and sampling devices

Instrumentation and sampling devices shall comply with the relevant design parameters.

Panels, covers, doors Panels, covers, doors

These parts shall be so designed such that they have no adverse influence (e.g. entrance and/or accumulation of soil) and shall be cleanable and, where required, capable of being disinfected.

Control devices Control devices

If there is no manual contact with the food, items or areas of equipment that are handled for control reasons by the operator, shall be considered as non-food areas. In the case of manual contact with the food, where cross-contamination can occur, these

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Splash area Splash area

Splash areas are to be designed and constructed following the same principles as those applicable to the food area. As the product does not return to the food area, the technical design criteria may be less stringent than in the food area in areas such as the following, provided that there is no adverse effect on the food:

• technical requirements for surface finish may allow for higher Rz and/or Ra

values;

• internal angles and corners may be of smaller radius, provided they are still cleanable and, where required, capable of being disinfected

• bearings, seals, moving shafts, etc., located in a splash area, may be lubricated by non-food grade lubricants, provided there is no adverse influence on the

food.

Non-food areas Non-food areas

In addition to the general requirements, exposed surfaces in the non-food area are to be made of corrosion-resistant material or material that is treated (coated or painted) so as to be corrosion resistant. These surfaces shall be cleanable and, where required, capable of being disinfected, and shall not contaminate or have any adverse influence on the food.

Equipment shall be designed and constructed in such a manner as to prevent the retention of moisture, ingress and harbourage of vermin, and accumulation of soil, and to facilitate inspection, servicing, maintenance, cleaning and, where required, disinfection. Tubular framing shall be completely closed or effectively sealed.

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Welding Welding

The best welding method for hygienic welds is TIG, as this has the best performance when welding thin-walled stainless steel tubes. Orbital welding with inert gas ensures high repeatability, resulting in welds of high quality.

Weld defects, such as cracks, porosity, etc., must be avoided to prevent the build-up of residues, minimising the risk of microbiological contamination to the lowest possible level.

The settings on the welding equipment (current, gas, etc.) are important, as well as preparation of the tubes. Misalignment, gaps, etc., should be avoided.

Steel quality: SS-2333, AISI 304 L Welding 2-pulse, O2content shown in ppm

It is important to visually inspect and check all welds. A fibroscope can be used to inspect welds inside tubes. Concavity, convexity, penetration, cracks, cavities, arc strikes and weld bead meandering must be considered in order to ensure a hygienic weld. It is also important to inspect the colour of the weld area as discolouration

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indicates the use of incorrect current or too high an oxygen content. Poor welds must be cut out and replaced by an approved weld.

Hygienic zoning Hygienic zoning

Zoning is understood as the physical segregation of different unit operations or activities including the use of physical barriers in regards to the hygiene level. Zoning is also used to control the movement of personnel, equipment and materials, as well as the circulation of ambient air.

Preventing the contamination of a product involves protecting the product, not only in the vicinity of, for example, a filling line, but also in the entire process area, or zone. Therefore, zones are defined according to the level of cleanliness and hygienic classification, to protect different types of products from, for example, various vectors carrying microorganisms (cross-contamination), pests and odours srcinating from the factory environment and its surroundings.

Hygienic zones are normally defined in two or three levels of hygiene, such as the ‘Basic Hygiene Zone’, ‘Medium Hygiene Zone’ and ‘High Hygiene Zone’.

Basic hygienic zones

Basic hygienic zones require Good Manufacturing Practice (GMP) and can be used to separate the area from outside areas. Typical basic hygiene zones are in the warehouse or incoming material reception areas. The milk reception area is also a basic hygiene zone. Personnel in this zone are not required to wear special clothing, but their clothing must be clean at all times. There should be no open product

handling in this area.

Medium hygiene zones

Medium hygiene zones also require GMP. Examples are process areas where products are made for consumer groups that are not especially sensitive, or products

in which no further microbiological growth is possible in the final product. Areas in which closed equipment with much higher internal hygienic requirements is operated (e.g. most of Tetra Pak Processing and Filling equipment), are often defined as medium hygienic zones. Personnel clothing must be clean, and white coats and protective headwear (hairnets) must be worn. Changing of shoes for operators or shoe

covers for visitors may be recommended, but are rarely essential. Filtered and conditioned air at an overpressure is recommended for certain applications.

High hygiene zones

High hygiene zones are those in which processed products are exposed and are vulnerable to recontamination. This classification is typical for open processes or operations in which the highest level of hygienic precautions must be adopted. This zone should be limited in size, and the layout should be as simple as possible.

Supplementary equipment such as fans, pumps, power supplies, etc., should be placed outside the area. Special rules are applied in such zones, for example, restricted movement of personnel and materials. Protective clothing, changing of shoes, etc., is

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essential before entering. Filtered (HEPA filter) and conditioned air at an overpressure is essential to minimise possible sources of contamination. Dry or controlled wet cleaning procedures are normally required for such areas. High hygiene zones are never subject to wet cleaning.

Note:

Note: Zoning should be used as a preventive measure, as part of the total hygiene concept. Zoning alone does not prevent contamination if the surfaces in contact with, or very close to, the product are not properly cleaned and maintained.

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Flow systems Flow systems

It is of the utmost importance to avoid the mixing of cleaning solution and product, or heat-treated and non-heat-treated product. In order to avoid this, different flow solutions can be used, such as swing bend plates, mix-proof valves or separation by valves and a drainable pipes. The three examples below show recommended flow solutions.

Examples of mix-proof arrangements

Valve arrangements for tanks - Filling and emptying from the bottom of the Valve arrangements for tanks - Filling and emptying from the bottom of the tank

tank

When filling and emptying a tank with a single bottom connection, a valve arrangement such as that shown in Fig. 2 can be used.

Fig. 2.

Fig. 2. Valve arrangement

V1 = Change-over valve, 3 gates for connection of CIP pressure V2 = Stop valve

V3 = Change-over valve, 4 gates to separate tank cleaning, pipe cleaning V4 = Change over valve, 3 gates for connection of CIP return

V5 = Change-over valve, 3 gates for bypass during pipe cleaning V6 = Change-over valve, 3 gates for bypass during pipe cleaning

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Cleaning of tank with mix-proof valves Cleaning of tank with mix-proof valves

Fig. 3.

Fig. 3. Cleaning of tank with mix-proof valves.

Cleaning of inlet/outlet backwards with pressure Note:

Note: It is possible to clean the inlet or outlet line with product in the tank.

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Cecili a Svenss on And ers Görans son 2008-11-14 1 24 (83)

Common tank bottom inlet/outlet LKB/SBP Common tank bottom inlet/outlet LKB/SBP

Fig. 4.

Fig. 4. Common tank bottom inlet/outlet LKB/SBP.

Application Application

This design shows the arrangement of the connection of a tank to CIP and production using a swing bend panel.

Functions during production Functions during production

When running the transport to the tank the swing bend must be in the horizontal position, as shown on the diagram.

Cleaning the tank Cleaning the tank

When cleaning the tank the swing bend must be in the vertical position. CIP return is on the right side of the swing bend panel. The valve in the bottom of the tank is to be flipped without pressure during certain steps in the CIP sequence.

Cleaning the inlet/outlet pipe Cleaning the inlet/outlet pipe

When cleaning the inlet/outlet pipe the swing bend must be in the vertical position. CIP return is on the left side of the swing bend panel.

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Instruction handbook Instruction handbook

An instruction handbook shall be provided by the manufacturer, which must meet several requirements including the requirement set out in EN ISO 12100-2:2003. Specific information related to the hygienic design is to be provided, in particular:

• Space required for operation and maintenance, for example, measures to be taken when installing equipment. Care shall be taken to ensure that there is adequate access for servicing the equipment and for cleaning service systems and their adjacent areas, so that the required level of hygiene can be

maintained.

• Acceptable environmental operating conditions and, where required, measures to be taken to ensure that the food is not adversely influenced by, for example, air currents, dust or liquids derived from leakage, condensation or aerosols.

• Dismantling (if necessary), cleaning, disinfection, rinsing and inspection for control of cleanliness. The method and frequency of cleaning various surfaces, including dismountable parts, are, however, dependent on the food

product being processed and the associated/relevant hazard(s). • Recommended cleaning and disinfecting agents and instructions for

dismantling (if necessary), cleaning, disinfection, rinsing and inspection to ensure cleanliness.

• The method and frequency of cleaning various surfaces, including

dismountable parts, are dependent on the food product being processed and the associated/relevant hazard(s).

• A scheme describing the measures required to ensure that the necessary level of hygiene of food equipment is maintained within specified intervals. • If food grade lubricants are required, this must be specified.

2.4 Hygienic Risk Ass essment

Performing a hygienic risk assessment of the design will indicate the relative significance and the need for higher levels of protection (i.e. safeguarding). Hazards are to be eliminated, or the associated risks reduced by ensuring that the equipment is properly designed and constructed, and capable of being properly installed, operated, cleaned and maintained. The hygiene requirements of the different parts of the equipment depend on their function, the type of food to be processed, and the nature of the hazards to the food. The primary objective of applying design and construction criteria is to eliminate or reduce the risks to an acceptable level. The mandatory hygiene risk assessment at Tetra Pak follows the methodology described in Tetra Pak Corporate Standard, document No. KA 2153.05, which is based on the methodology described in EN 1672-2:2005.

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2.5 Hygienic Design Checkl ist – Machin es and Peripheral

Equipment

CE marking

- hygienic design, possible to clean (MD 98/37/EC, Annex 1, paragraph 2.1)

- HRA performed according to EN 1672-2:2005

- withstand product pressure/volume (PED 97/23/EC) Suitable materials for product contact surfaces

- stainless steel (and other metals): quality suitable for the food to be processed

- elastomers and plastics: quality suitable for the food to be processed

- appropriate surface finish (USA & EHEDG 0.8μm)

Lubricants

- NSF-approved food grade lubricant: zero content in food in the EU, in USA < 0.1 mg/l is permissible

Joints

- permanent joints shall be sealed; crevices, inside shoulders, dead spaces, etc. are to be avoided

- dismountable joints shall exhibit a true and hygienic fit Drainage

- the equipment should preferably be self-draining Internal angles and corners

- shall be cleanable and, where required, capable of being disinfected, Rmin = 3 mm

Dead ends

- shall be avoided unless technically impossible in the design, max recommended length 1.5 x diameter

- if unavoidable, they shall be drainable/cleanable and capable of being disinfected

Fasteners

- screws, bolts, rivet, etc., shall be avoided Hygienic welds

- approved certified welder

- suitable welding method with correct parameter settings

- orbital welding preferred: tungsten electrodes and inert gas, recommended O2

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- inspection and approval of welds (use appropriate method; visual, video scope, X-ray, etc.)

Bearing and shaft entry points

- preferably located outside the food area, unless technically unavoidable

- shaft seals and moving shafts in the food area shall be self- (or product-) lubricated

- if technically impossible, they must be lubricated with food grade lubricant

- shall be cleanable and, where required, capable of being disinfected Panels, covers, doors

- must be designed to avoid any adverse effects, to be cleanable and, where required, capable of being disinfected

- control devices can normally be considered as non-food areas Splash area

- designed and constructed following the same principles as for the food area Non-food area

- corrosion-resistant material or material that is inert (i.e. has no influence on food) and cleanable

2.6 Hygienic Design Checkl ist – Proc ess Lin es & Plants

CE marking

- hygienic design, possible to clean (MD 98/37/EC, Annex 1, paragraph 2.1)

- HRA performed according to EN 1672-2:2005 or EN ISO 14159:2002

- withstand product pressure/volume (PED 97/23/EC) Suitable materials for surfaces in contact with food

- stainless steel (and other metals): quality suitable for the food to be processed

- elastomers and plastics: quality suitable for the food to be processed, EU reg. 1935/2004 or FDA

- correct surface finish (USA & EHEDG 0.8μm)

Lubricants

- NSF-approved food grade lubricant is to be used; in EU no presence in food, in USA < 0.1 mg/l

Suitable components for the food to be processed

- material approved for food contact

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- positive pumps cleanable (by-pass valve)

- masking of feedback signals, forced control, etc. (control system must not affect hygienic design)

- instrumentation and sampling devices must comply with the relevant design parameters

Hygienic welds

- approved certified welder

- suitable welding method with correct parameter settings

- orbital welding preferred: tungsten electrodes and inert gas, recommended O2

level 40 – 50 ppm

- pipe alignment

- inspection and approval of welds (visual, videoscope) Cleaning circuits

- number of objects -fouling of cleaning solution

- number of circulations (reuse) before reject

- flow rate of cleaning solution >1.5 m/s

- no mixing of product and cleaning solution possible, drainability

- no simultaneous upper and lower flip on Unique valves Pipe support

- pipe slope rec. 3%

- expansion aid used to avoid risk of tension

- valve clusters not used to support pipes, risk of tension – intercrystalline corrosion

Positioning/layout

- building and other premises acc. to Codex principles

- hygiene zones with transfer barriers (air pressure, air filter quality, PPE, etc.)

- possible to inspect and maintain equipment

- possible to clean equipment externally (non-food area)

- insulation properly mounted and suitably sealed Utilities

- culinary steam quality in food contact

- potable water quality in food contact and for cleaning purposes

- sanitary compressed air in food contact (filter quality, oil- and condensation-free)

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3. CIP Techn ol og y

The result of cleaning depends on a range of factors, including the type of product being processed, the quality of the raw material/product, the configuration of the

equipment, running time before CIP, type of cleaning solution, detergent

concentration, water quality, cleaning time, cleaning temperature, and flow rate of CIP solutions.

Factor Consequences

High quality of raw product Improved protein stability Type and configuration of equipment Running time restriction

Type of product Type of soil (mineral/fat/protein)

Running time before cleaning Thickness of soil layer Type of detergent Alkali, acid and additives

Detergent concentration Water quality

Cleaning time Cleaning result Cleaning temperature

Flow rate

3.1 Diff erent Types of Soil

It is important to know the composition of the soil when designing a CIP sequence. The composition of soil will vary depending on the type of product being processed. Simply changing the fat content of milk can result in a change in the composition of the soil, which makes it more difficult to remove. Tetra Pak process equipment is used for different food applications, ranging from juices to prepared food such as rice pudding and Béchamel sauce. Table 1 shows a schematic overview of the different types of soil that need to be removed from equipment surfaces during CIP.

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Table 1.

Table 1. Different types of soil (according to Guthrie, 1972). From the Handbook of Hygiene Control in the Food Industry (Ed. Lelieveld, H. L. M., Mostert, M. A. & Holah, J., CRC Press, 2005)

Type

Type of of soil soil Solubility Solubility Ease Ease of of removalremoval Low/medium

pasteurisation

High

pasteurisation/UHT Sugar Soluble in water Easy Caramelisation,

more difficult to clean

Fat Not soluble in water, soluble in alkali

Difficult Film formation, more difficult to clean

Protein Not soluble in water, soluble in alkali, slightly soluble in acid

Very difficult Very difficult

Mineral salts Solubility in water varies, most salts soluble in acid

Varies Varies

Starch Soluble in water and alkali

Easy to moderate Glue-like

formation, difficult to remove

Two examples are given below of the fouling that can be found in Tetra Pak processing equipment, srcinating from milk production and tomato paste production. Both products represent typical soil situations, but also serve to

illustrate the differences in the CIP cycles.

Milk fouling

During the processing of milk, either pasteurised or UHT milk, the heating equipment is fouled. There are two main types of fouling (see Table 2). Low-temperature pasteurisation (maximum Low-temperature 72-75 °C) creates a kind of fouling with a high content of protein, mainly β-lactoglobulin. This type of fouling is denoted type A, and is dominant in the temperature range 70 to 105 °C. During the production of UHT milk, another type of fouling besides type A fouling, denoted type B, arises. Type B fouling is created in the high-temperature range starting at 110 °C. This type of fouling contains a higher level of minerals than type A fouling, mainly calcium phosphate.

Table 2.

Table 2. Composition of soil in dairy applications. Type

Type of of fouling fouling (Type (Type A)A) % % (Type B) (Type B) % % Protein 50-60 15-20

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Tomato paste fouling

When cleaning a protein deposit, e.g. milk fouling, the detergent solution will cause swelling of the soil. Deposits resulting from the processing of tomato paste are cohesive, and can be removed in large chunks by hydration of the deposit–substrate interface. Fouling deposits form as a result of both adhesion of material to the equipment surface and cohesion between elements of the material.

3.2 Water Chemistry and Quality

Two main issues are of importance regarding water quality, namely microbiological status and water hardness. The microbiological status is the more important one in food processing. The other issue, water hardness, concerns the amount of metal ions in the water. Water hardness and inadequate pre-rinsing are two major factors causing failure in CIP operations, apart from inadequate flow rates. Calcium and magnesium ions are considered in the context of water hardness, but other polyvalent cations may also be of importance. The European standard for water

hardness is German degrees (°dH).

Three problems causing failure of CIP: • water hardness

• inadequate pre-rinsing • too low flow rate (Sect. 3.8)

Water hardness can be discussed in terms of carbonate hardness (temporary hardness) or non-carbonate hardness (permanent hardness). The salts causing permanent hardness are Ca and Mg sulphates or chlorides. Temporary hardness is

remedied by heating the water. The total water hardness is defined as the sum of the calcium and magnesium concentrations, expressed as equivalent calcium carbonate, according to:

mg equivalent CaCO3/l = 2.4797 ⋅ [Ca, mg/l] + 4.118 ⋅ [Mg, mg/l]

When referring to water hardness, it is essential to make it clear whether one is referring to temporary, permanent or total hardness.

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Table 3.

Table 3. Water hardness according to The Orange Book. Hardness CaCO Hardness CaCO33 mg/l (ppm) mg/l (ppm) German German dH dH Milliequivalent/l Milliequivalent/l meq/l meq/l Very soft <50 2.8 1 Soft 50-100 2.8-5.6 1-2 Moderately hard 100-200 5.6-11 2-4 Hard 200-400 11-22 4-8 Very hard >400 >22 >8 Table 4.

Table 4. Conversion table for water hardness units (The Orange Book). 1 °dH = 17.9 mg CaCO3 / l

1 meq/l = 50.0 mg CaCO3 / l

1 °f = 10.0 mg CaCO3 / l

1 ° Clark = 14.3 mg CaCO3 / l

1 grain/US gal = 17.1 mg CaCO3_{/ l}

Water quality can vary depending not only on the source, but also the time of day. Some naturally soft water can cause corrosion due to its acidic pH. Mineral salts make water more basic (pH above 7) and corrosion increases, leading to a high risk of damage to pipelines, heat exchangers and boilers.

Table 5.

Table 5. Water quality recommendations for minimum corrosion (ppm or mg/l). Hardness 4 – 7 °dH Alkalinity > 0.6 meq/l Chloride ions < 30 ppm Cl -Chlorine < 0.2 ppm Cl2 pH 7.0 – 8.5 Sulphate ions < 100 ppm Aluminium < 0.1 ppm Iron < 0.2 ppm Manganese < 0.05 ppm KMnOconsumption 4 < 20

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3.3 CIP Theor y

Cleaning of processing equipment is a necessity for all food producers. CIP should be planned in such way that it intrudes as little as possible on production time. In

order to reduce CIP times it is important to consider the process as a whole. Cleaning is not an isolated event, and product recovery preceding CIP can be performed in an intelligent way. In many UHT applications, production starts

immediately after cleaning, and thus the sterilisation of the process equipment must also be considered as part of the cleaning cycle.

The factors influencing the cleaning of processing plants are mechanical design, process design and cleaning process. The interrelationships between these is

illustrated in the figure below (Fig. 5). It can be seen how the process design is related to the cleaning process through the type and amount of fouling on the equipment surface. The type of detergent and concentration must be chosen so as to be appropriate for the type of fouling. The mechanical design then governs both the process design and the cleaning process. Designing and managing cleaning

processes is extremely important, but before all else – processing equipment must be designed for hygiene.

Mechanical design

- materials, surface finish

- equipment design and installation

- geometry

Process design

- quantity and type of soiling

- age/moisture of soiling

- composition of soiling

Cleaning process

- detergent type and concentration

- temperature

- flow rate

- water hardness

Fig. 5.

Fig. 5. The relations between the factors affecting the cleaning of a food processing plant.

Designing and managing cleaning processes is extremely important, but before all else – processing equipment must be designed for hygiene.

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The cleaning steps after pre-rinsing can be described in the following steps, which are illustrated schematically in Fig. 6.

1. The cleaning solution is transported to the fouling layer by the fluid flow (turbulence).

2. The detergent reacts with the surface of the fouling layer and the chemicals start to penetrate the layer. Proteinaceous fouling starts to swell.

3. The dissolved fouling layer is then transferred to the bulk solution. It is possible to prevent the soil from aggregating and re-attaching to the fouling

layer by using additives.

Fig. 6.

Fig. 6. Illustration of the cleaning mechanism. (from Jeurnink and Brinkman)

.

Rinsing water

Alkaline cleaning solution

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Fig. 7 illustrates Zinner’s circle consisting of the four main process parameters that can be controlled during CIP: the concentration of the cleaning agent, temperature, time and flow. Zinner’s circle is surrounded by a circle representing the production time. A longer production time usually results in a longer cleaning period. This in turn may result in a longer down time. Therefore, production time must be considered as well as the specific product being processed.

Fig. 7.

Fig. 7. The parameters that affect the cleaning result. Time

Flow

Concentration

Temperature

It is important to know which of these four parameters is the most important. In order to reduce costs and energy consumption it is important to optimise the CIP sequence. The cost of the energy required to heat the CIP solutions, the energy needed to pump the CIP solutions and the price of the CIP solutions should thus be compared. In the broader perspective CIP must be included in the total production scenario.

In the following sections the different aspects of cleaning will be considered in more detail, starting with the chemistry of cleaning.

3.4 Detergent Chemistry

Many dairy producers today use lye (sodium hydroxide solution) and an acid as cleaning agents. This is sufficient for many applications and results in adequate

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chelating agents and acids, and it is important to choose the most suitable component or components based on:

• the kind of fouling to be removed • the detergent

• the concentration, temperature and contact time • the quality of the water

The function and effectiveness of various detergent compounds are summarised in Table 6, on a scale from 1 to 5, where 5 indicates excellent functionality.

Table 6.

Table 6. The effectiveness of various cleaning compounds (from the Handbook of Hygiene Control in the Food Industry, Ed. Lelieveld, H. L. M., Mostert, M. A. & Holah, J., CRC Press, 2005) Cleaning Cleaning function function Strong Strong alkalis alkalis Mild Mild alkalis alkalis Polyphosphates Polyphosphates (sequestering (sequestering agents) agents) Weak Weak acids acids Strong Strong acids acids Surfactants Surfactants Chelation 1 2 5 1 1 1 Saponification 5 4 4 4 4 2 Wetting 2 3 2 2 1 5 Peptising 5 4 2 3 4 1 Emulsification 2 3 3 1 1 5 Dispersion 3 4 2 4 1 4 Rinsing 4 4 3 2 1 5 Corrosion 5 3 1 3 5 1 Alkalis

If the fouling consists of proteins an alkali is the best cleaning agent. The most frequently used alkali detergents are sodium hydroxide (NaOH), potassium hydroxide (KOH) and sodium carbonate (Na2CO3). Alkalis cause the proteins to

swell, facilitating their removal. In order to reduce the cleaning time the pH of alkali solutions should be between 12 and 13 (Table 7).

Fat is also removed by alkali. At high temperatures fat is saponified, i.e. soap is formed. Soaps also lower the surface tension of solutions thus improving the emulsification of fat and the wetting effect.

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Sodium hydroxide (NaOH) has excellent detergent properties but corrodes

aluminium, galvanised metal and tin. Its rinsing and wetting properties are poor, and divalent metal ions (Ca2+ and Mg2+) are precipitated in alkaline solutions. If hard water is used for rinsing and/or preparation of the cleaning solutions, this will add to the mineral-based fouling of the equipment.

Table 7.

Table 7. pH as a function of concentration for two alkali detergents. Concentration

Concentration 0.25 0.25 0.5 0.5 1.0 1.0 2.02.0

NaOH 12.5 12.8 13.0 13.3

Na2CO3 11.3 11.4 11.6 11.7

The use of NaOH with hard water will add to the mineral-based fouling of the processing equipment.

Acids

The hydrogen ion (H+) in acids reacts with the fouling causing it to break down and dissolve. The most frequently used inorganic acids are nitric acid (HNO3) and

phosphoric acid (H3PO4). The former is most frequently used in Europe, while the

latter is the first choice in the USA. Nitric acid is a stronger acid, having a higher coefficient of dissociation than phosphoric acid, and is thus more efficient, but it is also more corrosive to stainless steel. Among the organic acids, acetic acid, lactic acid, citric acid and gluconic acid are the most frequently used. These acids are weaker than, and not as corrosive as, nitric acid but expensive compared with the above mentioned inorganic acids. Hydrochloric acid (HCl) must not be used due to its corrosive properties on stainless steel. However, chlorine detergents are

commonly used in membrane cleaning applications due to their high oxidising capability.

In many applications alkali CIP is followed by acid CIP. However, inorganic acids have strong dissolving effects on protein fouling and can thus be used before alkali CIP in order to facilitate cleaning with an alkali detergent. Due to the passivating effect of acids on stainless steel, acid detergents are used after alkali CIP. In the cleaning of UHT milk processing equipment, especially in high-temperature parts of the steriliser, minerals and the white deposit called milk stone are removed by acid cleaners.

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thus making cleaning more efficient. They also prevent re-deposition of fouling material on the surface through electrostatic interactions or steric hindrance.

As can be seen in Table 6, the function of these compounds in CIP detergents is to improve the physical dispersion, emulsification, foaming and wetting of the fouling layer. Surfactants may be ionic or non-ionic. The ionic surfactants are divided into three sub-classes: anionic (negatively charged in water), cationic (positively charged in water) and amphoteric (charge is pH dependent). Amphoteric surfactants are cationic under acidic conditions and anionic under alkaline conditions. The active components in these substances are tensides, which means they have a hydrophilic part (from the Greek for water-loving) and a hydrophobic part (from the Greek

water-rejecting). This enables them to act as a binder between the hydrophilic water and the hydrophobic fat.

Ionic surfactants

Anionic wetting agents can be classified into five groups: sulphated alcohols, sulphated hydrocarbons, aryl alkyl polyether sulphates, sulphonated amides and alkyl aryl sulphonates, which have good to excellent detergency. Both the removed foulant and the equipment surface become negatively charged, thus preventing re-deposition. However, in the presence of Ca2+ or Mg2+ ions the effect will be the opposite, and therefore sequestering agents should be added to these detergent solutions.

Cationic wetting agents consist of quaternary ammonium compounds. This group of wetting agents exhibits lower cleaning efficiency than anionic and non-ionic wetting agents, and is not used for the cleaning of food processing equipment.

Amphoteric wetting agents act by loosening and softening protein- and carbohydrate-rich soil, and are widely used in the food processing industry.

Non-ionic surfactants

These surfactants are best employed when removing soil consisting of oil, and are affected little by water hardness. The working principle is to sterically prevent the removed soil from returning to the equipment surface or aggregating in the bulk solution.

Sequestering Agents (chelating agents)

The function of sequestering agents is to bind to calcium and magnesium ions in order to soften water. The ions are bound so securely that they can no longer react to form so-called milk stone or calcium soaps. Common sequestering agents are orthophosphate, orthosilicate and phosphates. It is important to bear in mind that the waste water evacuated to the drain contains phosphates, which can be an

environmental problem.

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molecule in contrast to sequestering agents, which can bind to a number of metal ions. The most common complex-forming agents are EDTA (ethylene diamine tetra acetic acid), NTA (nitrilo-tri acetic acid), IDS (imido-disuccinic acid) and

gluconate.

Oxidation Agents

Formulated alkaline detergents produced by detergent manufacturers can contain oxidation agents to boost their cleaning effects. Examples of such substances are oxygen-releasing agents, active chlorine or active-chlorine carriers. These may be in a liquid form, such as sodium hypochlorite, hydrogen peroxide or potassium

hypochlorite, or in powder form, such as sodium perborate or sodium percarbonate.

They are added in a stabilised form, and active oxygen is cleaved off over a certain period of time. They create new sites for detergents to act.

Summary of the different detergents used in food Summary of the different detergents used in food equipment cleaning: equipment cleaning: Alkalis Alkalis - NaOH - KOH - Na2CO3 Acids Acids - HNO3 - H3PO4 Wetting agents Wetting agents

- Ionic (anionic, cationic and amphoteric)

- Non-ionic Sequestering agents Sequestering agents - EDTA - NTA - IDS - Gluconate Oxidation agents Oxidation agents - Sodium hypochlorite - Hydrogen peroxide

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Overview of Some Cleaners and Disinfectants

Below follows an overview of acid descalers and cleaners, neutral cleaners, alkaline cleaners and disinfectants.

Table 8.

Table 8. Acid descalers and cleaners (from the Handbook of Hygiene Control in the Food Industry).

Ingredient

Ingredient Substance Substance FunctionFunction

Inorganic acids Nitric acid Owing to its oxidising properties at high concentrations nitric acid cannot be used in complex formulations, e.g. with surfactants. Its use is limited to descalers for removing inorganic residues such as water scale and milk stone from surfaces.

Phosphoric acid Sulphonic acids Sulphuric acid

These acids can be combined with surfactants, defoamers and other components in cleaning agents, and may be used in formulations designed to simultaneously remove inorganic and organic residues from food contact surfaces . Organic acids Formic acid

Citric acid Lactic acid Gluconic acid Sulphamic acid

See phosphoric acid

Inhibitors Phosphonic acids Protect materials against chemical attack. Surfactants Non-ionic and

anionic surfactants

Improve cleaning efficacy regarding organic soil; enhance scale-removing properties and are the choice for removing fat residues.

Defoamers Hydrophobic

non-ionic substances

Suppress foam arising from formula components and/or removed soil.

Stabilisers Hydrotrophic substances

Stabilise liquid formulations at high and/or low temperatures.

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Table 9.

Table 9. Neutral cleaners (from the Handbook of Hygiene Control in the Food Industry).

Ingredient

Builders Phosphates

Phosphonates Citrates

Enhance soil-removal and suspension properties as well as the effects of surfactants.

Surfactants Non-ionic and anionic surfactants

Allow soil penetration and emulsification, and provide better surface wetting.

Defoamers Hydrophobic non-ionic substances

Enzymes Proteases Improve protein removal at around neutral pH from sensitive surfaces.

Lipases Improve fat removal without using surfactants.

Specific enzymes Improve removal of recalcitrant substances from surfaces without using aggressive chemicals.

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Table 10.

Table 10. Alkaline cleaners (from the Handbook of Hygiene Control in the Food Industry).

Ingredient

Bases Sodium hydroxide

Potassium hydroxide

Solve, peptise, soften or decompose organic soil.

Chelates EDTA

NTA IDS Gluconate

Chelates not only reduce the negative effect of water hardness on cleaning efficacy and provide scale prevention, they can also remove fresh, thin layers of

inorganic deposits, attack inorganic soil and help in removing organic soil when combined with inorganic scale.

Builders Phosphates

Phosphonates Citrates Silicates

By chemical nature most of the builders are chelates. They enhance soil-removal and suspension properties as well as the effects of surfactants.

Surfactants Non-ionic and anionic

Improve soil penetration and emulsification, as well as surface wetting.

Sequestering agents

Polyphosphates Phosphonates

Prevent scaling, especially in rinsing stages.

Corrosion inhibitors

Silicates Protection of soft metals against chemical attack.

Oxidising cleaning boosters

Hypochlorites Assist in removal of recalcitrant and insoluble soil. They can break down larger molecules into smaller fractions by means of oxidation, or render soil soluble by introducing functional groups.

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Table 11.

Table 11. Disinfectants (from the Handbook of Hygiene Control in the Food Industry).

Ingredient

Ingredient Substance Substance FunctionFunction Disinfectants Hypochlorites Peroxides Quaternary ammonium compounds Ampholytes

To kill microorganisms by complex reactions on either the outside or inside of the microbial cell.

pH-regulators, buffers

Bases Acids Salts

To provide optimum pH for the active biocide, stabilise the pH during application, e.g. to reduce the risk of corrosion

with oxidising disinfectants, or to provide product stability in solution or in concentrated form.

Surfactants Non-ionic and anionic surfactants

To improve wetting, enhance biocidal efficacy and enable foam applications.

To control foaming during cleaning Stabilisers Hydrotrophic

substances

To stabilise liquid formulations at high and/or low temperatures.

3.5 Detergent Concentration

When cleaning fails the natural reaction is to increase the concentration of the detergent. However, this may be counterproductive. A number of investigations into milk fouling in the pasteurisation temperature range have indicated an optimum NaOH concentration in the range 0.5-1% (w/w) (see Fig. 8). This can be explained by the fact that an increase in the NaOH concentration does not increase the

cleaning rate, but instead results in a glassy surface on the soil, preventing the cleaning solution from penetrating it.

The cleaning procedures used in the dairy industry involve a higher lye

concentration than that mentioned above (0.5-1%). The reason for this is that these plants are more heavily soiled and lye is consumed during cleaning.

However, it is important to bear in mind that increasing the detergent concentration may not solve cleaning problems. Many investigations have shown that there is an optimum detergent concentration and that increasing it will lead to less effective cleaning. The optimal concentration varies depending on the type of detergent, e.g. pure NaOH, NaOH with additives or formulated detergents from a detergent

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0 0,2 0,4 0,6 0,8 1

Lye concentr ation / %

C l e a n i n g t i m e / a . u . Fig. 8.

Fig. 8. A number of investigations of milk fouling in the pasteurisation temperature range have indicated an optimum in NaOH concentration in the range 0.5-1% (w/w). The optimal concentration varies with the type of detergent.

The solution might not be to increase the detergent concentration when encountering cleaning problems. Consider other cleaning parameters, such as flow rate, temperature and cleaning time.

Dosing of Cleaning Agents

The goal is to obtain an even distribution of the cleaning agent throughout the whole equipment. Cleaning agents can be dosed directly or in-line. The advantage of using in-line dosing is that the correct detergent concentration will be obtained for that particular piece of equipment or plant. To obtain the best effect with in-line dosing, both the flow and the dosing frequency should be high, making the distribution

more even.

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Fig. 9.

Fig. 9. The principle of in-line dosing. (From the Handbook of Hygiene Control in the Food Industry.) Top left: high flow velocity and low dosing frequency, resulting in a poor distribution of the detergent. Top right: changing the dosing volume will not result in a better distribution. Bottom: the best alternative is to maintain a high flow velocity and increase the dosing frequency.

When using in-line dosing high demands are placed on measuring and controlling the detergent concentration. This is normally achieved by measuring the

conductivity in-line. Table 12 gives the conductivity for various solutions at 20 °C. It is important to remember that the conductivity is strongly dependent on

temperature, as is shown in Fig. 10. The conductivity sensors used today are temperature calibrated.

Table 12.

Table 12. Conductivity of different solutions at 20 °C (from the Handbook of Hygiene Control in the Food Industry).

Solution

Solution Conductivity Conductivity @ @ 20 20 C C (mS/cm)(mS/cm)

Tap water, soft 0.18 Tap water, hard 0.46 Tap water, saline 0.75

Brackish water 2

NaOH 1 % w/w 47.5 NaOH 2 % w/w 90.0 NaOH 3 % w/w 127.0

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0 50 100 150 200 250 300 350 10 20 30 40 50 60 70 80 90 Temperature (C) C o n d u c t i v i t y ( m S / c m ) 1.0% w/w NaOH 2.0% w/w NaOH 3.0% w/w NaOH Fig. 10.

Fig. 10. Conductivity vs. temperature for three NaOH concentrations (from the Handbook of Hygiene Control in the Food Industry).

3.6 Cleanin g Temperatu re

Chemical reactions generally proceed faster at higher temperatures. This is also the case when cleaning solutions react with foulants. It is generally said that the effectiveness of an alkali solution will double for every 8 °C increase in

temperature. This has been demonstrated for the removal of proteinaceous deposits at cleaning temperatures up to 80 °C, but is probably also true for higher

temperatures. It can clearly be seen in Fig. 11 that increasing the cleaning temperature when removing protein fouling from a pasteuriser increases the cleaning rate.

It is important to remember that the production temperature must not be exceeded when cleaning the processing equipment, especially when removing proteinaceous foulants. If this temperature is exceeded, the proteins may be denatured, making the deposit more difficult to remove.

Guideline Guideline

Do not exceed the production temperature during CIP since proteins may be denatured, making the deposit more difficult to remove.

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60 70 80 90 Temperature / C T i m e t o c l e a n / a . u . Fig. 11.

Fig. 11. The influence of temperature on cleaning time.

Table 13 gives some general guidelines for choosing CIP temperatures for some typical cleaning objects in a dairy process line.

Table 13.

Table 13.Suitable cleaning temperatures for the cleaning of equipment in the dairy industry (from the Handbook of Hygiene Control in the Food Industry).

Type of Type of detergent detergent Temperature Temperature (( C)C) Equipment to be cleaned Equipment to be cleaned

HNO3 60-65 Tanks, pipes, milk pasteurisers

80-85 UHT plants

NaOH 60-80 Milk collection tankers, milk tanks, cream tanks, quarg and yoghurt tanks, filling machines

70-90 Milk pasteurisers

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3.7 Cleaning Time

Cleaning time is the most interesting parameter from the production perspective. The cleaning time places the focus on the fact that cleaning is to a large extent an optimisation issue. The milk producer does not want to clean longer than necessary, but the soil must be removed to ensure food safety. The cleaning time is correlated

to the specific equipment to be cleaned, thus it is of vital importance to characterise every piece of equipment when optimising the CIP sequence in order to identify the equipment that requires the longest cleaning time.

Another factor that must be taken into consideration when designing CIP sequences is the length of production time preceding cleaning, which is illustrated in Fig. 7. A longer production time will probably result in the need for a longer cleaning period. The third factor that affects the cleaning time is the type of product that has been processed, chocolate milk being harder to remove than normal milk, for example.

Several steps are included in the cleaning process that do not involve the use of cleaning solutions, such as pre-rinsing, inter-rinsing and final rinsing. The cleaning steps involving detergent require enough time for the solutions to dissolve the soil, swell it, saponificate it, disperse it and finally remove it. The detergent must be in contact with the foulant long enough to ensure that it is completely removed from the surface of the equipment.

Cleaning time depends on:

- the kind of equipment to be cleaned

- the production period prior to cleaning