Important Instructions and Precautions for Cip System

1) Use of “Material Safety Data Sheet (MSDS)” provided by the manufacturers is very important as every detergent and sanitizers has its specific handling requirement depending upon their reactive nature with handling personnel,equipment and surrounding atmosphere. In order to prevent unwanted harm one should read carefully the safety instructions given about the chemical and necessary application techniques. Most preferably these MSDS should be displayed near the place of use.

2) The washing machines are designed by keeping certain types of detergent/sanitizer characteristics in mind and hence manufacture’s recommendations must be looked into while selecting the detergent and sanitizers.

3) The milk lines should be isolated from the CIP circuit to prevent danger of contamination of milk with the detergent/acid solutions. Special care is required during circulating acid in the CIP system. Leakage of acid solution through defective, open valves may curdle the milk. The CIP line of the vessels/equipment containing milk should be preferably completely plugged off with he help of
proper size blanks.

4) Interlocking arrangement is also done for protection against intermixing of products and intermixing of products with cleaning solutions during CIP operations. Interlock circuits may have any desired condition mandatory prior to establishment of product transfer or CIP cleaning operation.

5) Other controls like level (high and low) control, temperature control are to be calibrated to ensure protection against unsafe operations.

6) Specially designed balls used for spay of detergent solutions in CIP process should be fitted properly and inspected for clogging of holes. Periodical cleaning ensures effective spray and cleaning.

sanitization in Cip Process

Sanitization process of equipment and containers is done after cleaning operation.The detail process and requirements is discussed in the unit-13: “Methods of cleaning and sanitization”. After cleaning is over, surfaces are properly rinsed and then according to the requirement sanitization is done. Where hot water sterilization is required, the heated water at about 80 to 85°C is passed through and circulated for 15 to 20 minutes. In other type of system, sanitizer solution of required concentration(depending upon the chemical used and level of sanitary condition is desired) is passed through and drained.

Features of Cip System

Following features are noteworthy in CIP systems:

 

i. The heating arrangements

Usually steam at 2 to 3 Kg/sq.cm. pressure is used for heating the CIP tanks. For this steam is supplied in the coils in the tank or jacket of the tank. It has been observed that steam heating provision in tanks results in water evaporation and creates unhygienic conditions and as such results excessive loss of heat. At the same time due to loss of temperature during supply from tanks to place of cleaning,there are chances of non-achievement of desired temperature in for the CIP of equipment. This problem is corrected in the modified CIP system, in which various solutions are heated to the required temperature in a plate heat exchanger placed nearer to processing equipment/vessel. This type of arrangement is not only energy efficient but on the other hand results effective cleaning due to better control over the temperature of cleaning solutions.

 

ii. The preparation of solutions

Following steps are taken for preparing various solutions in the tanks of CIP system:

•  Drain the dirty solution from the tanks and clean thoroughly.
•  Feed the tanks with required quantity of water by opening water line valves
•  Dose various detergent/acid/sanitizers in measured quantity in the respective tanks to get proper concentrations.
•  Open steam valve in the water tank, if hot water is required, otherwise not.
•  Heat the alkali and acid tank to achieve required temperatures.
•  Alternatively in the modified system where plate heat exchanger (PHE) is used for heating the solutions, pass the particular solution through the PHE and re-circulate till required temperature is achieved. Now forward the heated solution for the purpose of cleaning.

iii. Operation techniques of CIP system

The CIP system is operated with following three techniques, in which the solutions are taken from tanks, heated to a particular temperature and circulated for cleaning for desired period.

Manual System: In this type of system all the valves, pumps are operated manually by a trained operator.

Semi Automatic CIP System: This type of system are provided with pneumatic valves and operated through skilled operator and/or time/temperature control relays known as timer.

Automatic CIP System: In this type of CIP system all operations including maintenance of concentration, selection of tanks, cleaning equipment, duration and temperature of solution is done automatically as per the set cleaning programme of the plant. Since cleaning of milk equipment, process circuit and vessels are the repetitive in nature; hence use of automatic system demands application of automation. This type of system makes mandatory the application of two principles;namely, 1) proper engineering of the product piping system and a CIP supply-return system, and 2) the installation of a permanently located recirculating unit. The automatic system consist of a) program sequence controller to time all portions of the cleaning cycle, b) adjustable set-point temperature controls to provide variable supply-line solution temperature, c) air-operated solution flow-control valves, and d)detergent feed equipment to transfer chemicals automatically into the system as required for the cleaning processes.

 

 iv. Standalone type cleaning-in-Place system

There are number of dairy equipment in which centralized CIP system is not used and other special type of CIP arrangements are inbuilt or provided during installation.Milk/cream pasteurizer, milk evaporator/condensing plant are some such most prominent examples. In this type of process equipment similar process as discussed above is carried out. However, these equipment are cleaned by their own flow circuit. The balance tank is used for taking water, dosing chemicals and feed pump to circulated the desired solutions of required concentration for certain period. The heating system of the equipment is used for heating the solution. One of the CIP circuit of milk pasteurizer (PHE) is depicted in the Figure.

CIP Circuit of Milk Pasteurizer

LEGENDS: C stands for chilling section, 1 stands for Regeneration-I, 2 stands for regeneration-II, H stands for Heating section,
Represents Cooling medium line, which is shut off during CIP, & Represents heating medium line (steam or hot water heating).

The solution after heating to required temperature in heating section goes to holding and then passes through FDV.

The CIP of milk pasteurizer is done mainly in three flow patterns; viz: a) by using regular product supply and discharge line, b) simple method of using split flow with few changes, and c) providing highest holding tube velocity.In the split flow technique,

In the split flow technique, various section of PHE have circulation of solution without production of excessive pressures and prevent excessive leakage through gaskets. In this about three times solution is forced through the plates as compared to the regular flow path, causing better filling of plate and air purging. However this requires high capacity of pump to force larger volume and need special size of inlet and outlets.

Procedure of Cleaning in Place of Process

The CIP process may be applied to process circuit (piping systems) and associated process equipment by re-circulating rinse, detergent, and sanitizing solutions through circuits comprising of re-circulating unit consisting of pump(s), valve(s) and supply tanks to perform series of above operations. The cleaning-in-place operation is usually done in the following manner:

•  Take clean and soft water of required quantity in each CIP tank (cool /hot water, detergent, acid and sanitizer tanks). Maintain the concentration and temperature of each tank. For this the tank should be fitted with temperature and pH indicators.
•  As soon as processing is over, flush the equipment/container/process circuit with clean and soft cool water so that residual milk/milk product comes out.
•  After flushing is over pre-rinse with clean water at normal ambient temperature for 10 minutes to loosen the adhered milk/milk product comes out.
•  Now circulate detergent solution of 0.5 to 1.0% concentration and maintain recirculation at 70 to 75°C for 25 to 30 minutes or as desired in the CIP design.
•  Now circulate hot water maintained at 80°C for 10 minutes.
•  If required to remove water scale and milk stone by circulating acid solution of 0.5 to 1.0 or as decided in the CIP programme of dairy at 65-70°C for 25 to 30 minutes. Usually acid circulation is done at certain set intervals (say one week or fortnight period) and therefore skip this step in the daily/routine CIP.
•  If acid is circulated then rinse by circulating water at ambient temperature for 10 minutes and then again circulate the detergent solution for 25 to 30 minutes as described in the previous step.
•  Flush with water for 10 minutes.
•  Circulate hot water maintained at 80o to 85°C for 15 to 20 minutes to get sterilization of the surface.

Cleaning in place (CIP)

Milk processing and handling equipment/containers are desired to be clean, dry and sanitized to prevent cross contamination of milk/milk product during handling & processing operations. Small and simple construction equipment could be manually cleaned with hand brushes and detergents. Some times these equipment/containers are dismantled and their parts are cleaned/sanitized individually. Some of this type of containers could also be cleaned through specially designed washing machines like can/crate washers. However there are number of other equipment, containers and processing circuits, which have very compact design and not possible to clean manually or they are so larger in size that unsuitable for cleaning in washing machines. This type of equipment and containers are preferably cleaned by special cleaning procedure termed as “Cleaning-In-Place or CIP”.

In the CIP process number of cleaning operations are performed on the equipment/container/processing circuits one by one in certain sequence according to the plant hygiene programme. In this way instead of taking equipment/containers to the detergent solution or washing machine for cleaning/sanitizing, the flushing/cleaning/sanitizing solutions are taken to them through specially designed cleaning system.

The experiments and industry experiences have shown highly effective result from the CIP system along with several other benefits in terms of saving of manpower,time and chemicals. The effectiveness of CIP system is largely dependant on factors like time,temperature, detergency and physical action involved The equipment susceptible to this technique of cleaning are said to be of CIP design. Most significant CIP design dairy process equipment include: milk chiller,milk pasteurizer, milk tanks/silo, evaporator/dryer, milk process line, milk tankers,etc.

Types of Can Washers

Many types of can washers have been developed and are commercially available for washing milk cans of different shapes and sizes. Popularly, following types could be observed in the dairy industry:

i. Can scrubber
ii. Can Steaming Block
iii. Rotary can washer
iv. Straight-through can washer

 

i. Can Scrubber

Design and Operator: These are very simple type of can washing machines. As shown in the Fig. one nylon fibre hard brush “A” of cylindrical shape revolves about its axis which is driven by small rating (usually 0.5 to 0.75 HP) electrical motor. Another brush “B” is driven with the connected gear. One stationary brush “C” to suit the shape of can is fitted at one sidewall of the scrubbing machine. The arrangement of these brushes are shown in the following schematic diagram (Fig)

Schematic Diagram of Can Scrubber

Following procedure is usually employed for washing cans in the scrubber:

•  Fill the washer and put the required quantity of detergent.
•  Heat the solution up to 45 to 50Oc.
•  Now start the motor of can scrubber to rotate the brushes.
•  Collect can from drip saver and insert it into the scrubber brush “A” from the free end side.
•  Hold the can for enough time to loose the deposited materials.
•  The brush “A” will scrub the inside surface of can, and rotating brush “B” and;stationary side brush of special shape will scrub the external surface of can.
•  Take out the cans and rinse with cold water.
•  Check the cleaning status with clean fingers.

Precautions: Major precautions required for effective operation of a can scrubber are:

Proper temperature, concentration of solution and enough holding/scrubbing time are important factors for effective washing. Being manually operated, low-temperature, concentration and holding time are kept at low levels to prevent irritation to the operator. For safety reasons operators should be provided with protective hand gloves. Condition of brush requires regular monitoring so that worn out set of brushes are replaced in time. The brushes after some period of operation either gets worn out or becomes of reduced diameter/thickness due to de-shaping/compression of fibers. With such worn out condition, brushes are not able to touch and scrub the surfaces leading to ineffective cleaning of cans.Care should be taken in adopting right procedure of charging the can scrubber.The clean/soft water is filled up to required level and then measured quantity of detergent is added followed by opening of the steam valve slowly to warm up the detergent solution.Concentration of the detergent solution is checked at desired interval of operation. If required, additional quantity of detergent is charged.The solution is drained after every 150 can washing and then recharged freshly.However, the interval could be changed after observing the practical requirements.

Maintenance: Apart from above routine precautionary measures following maintenance aspects need serious considerations:

•  Draining of dirty detergent solution and washing properly to keep the trough clean.
•  Checking all the brushes for proper alignment, tightening and condition of fibers. If found not proper set right properly. Change worn out brushes.
•  Checking motor and motion/power transmission system including chain/belt and sprocket/pulley for wear - tear and alignment.
•  Providing grease/oiling over the chain/gears
•  Checking glands to prevent loss of detergent solution.
•  Checking the drain plug to prevent leakage through it.

 ii. Can Steaming Block

After manual cleaning of cans, the sterilization is done either by spraying cold sanitizer solution or steam sanitization through steaming blocks (Fig).

Design and Operation: This equipment is specially designed for holding can in the inverted position. Paddle operated steam and water jets are used to rinse the washed can with cold water and sterilize by injecting live steam till the can becomes hot.

Schematic Diagram of Steaming Block

Precautions: Main precautions required in operating steaming block are to ensure steam opening and working of rinse/steam injection valve. The safety of operator who is holding the hot can need to be ensured to avoid burn. Some times, operator holds cans for less time which may result in an ineffective operation. In order to avoid accident from hot water spray, the can should be positioned and then rinse or steam valve is opened. Steam pressure of 2 to 3 kg/sq. cm is enough to get the effect.

Maintenance

•  Check and clean holes of jet regularly.
•  Check and adjust spring tension of paddle-operated valve.
•  Clear the drain water holes and maintain cleanliness.

  iii. Rotary Can Washer

These are semi-automatic or automatic can washing machines, in which cans are rinsed, cleaned and sterilized very effectively. The details of the machine are described below.

Design: The cans are carried on a large rotating table or carrier (Fig);this type of washer is very simple in construction. Deshaped cans are also cleaned without any problem of falling. These are built in various sizes for handling low to medium number of cans and are very compact machines.

Rotary Can Washer

Operation

•  The detergent tank is charged.
•  Temperatures of rinse water, detergent solution, heating air is set in the automatic type washer. In the semi automatic machine valves are opened to heat the liquid and temperature is monitored.
•  Start the machine to revolve the table, to operate pumps and to heat with the steam.
• Empty cans after draining milk at the drip saver are placed one by one manually or automatically on the revolving carrier/table of washer from the entry door
•  Cleaned and sterilized cans will come out from the unloading door.

Precautions: Check the effectiveness of cleaning. In case of dented cans or heavy soiled can, scrub the can in the can scrubber before loading in the rotary can washer.

Maintenance:

•  Like other can washer, pumps and nozzles are to be checked timely.
•  Lubricate the moving parts daily or as per the manufacture’s instructions.
•  Check and attend the gland/oil seal/water seal
•  Keep all the doors closed except entry and exit.

 iv. Straight-through Can Washer

Design and operation : The washer has rinsing, detergent spraying, hot water rinsing, steaming and air-drying sections (Fig.). The cans are moving from entry door over the steel or plastic chains of special design to hold the can and carry towards the exit door. In other type of moving arrangements cans are carried forward through a ratchet from one position to the next. Can moves forward from entry door in inverted position to rinsing section, where warm water is injected from bottom and other sides removing loosen soils and some part of dirt. Then these cans move to detergent section, in which hot detergent solution of 0.5 to 1% concentration is sprayed inside and out side surface of cans to remove the soil completely. These cans move to hot water rinsing section where the traces of detergent and soils are removed. Now, the cans are effectively clean and move to steaming section for sterilization. Finally the hot cans are dried into the air-drying section. Before reaching to exit door, by suitable attachment, inverted cans are brought to the normal position with mouth upside.

Two types of steam injection are presolent i.e. intermittent and continuous. The intermittent type jets give economy of saving steam.The cleaning operation can be accomplished in semi-automatically or automatically in the machine depending upon the technique employed.

Precautions

•  Steam jets should be cleaned regularly for proper injection of steam.
•  Damaged cans should not be used, as they often fall inside the washer and interrupt the washing operation.
•  Use steam and air at enough pressure & temperature.
•  Ensure that proper quantity of water is available to can washer.
•  Keep door closed while washing is in progress.

Maintenance: The following maintenance is required in straight through can washer to carryout the washing operation smoothly:

•   Check the steam nozzle before and after the washing operation. Clean the blocked nozzle.
•  Can conveying chain should be checked, loose link should be repaired/ replaced.
•  Clean all the tanks (water/detergent/hot water).
•  Inspect the oil seal/water gland of pumps.
• Check the door gaskets and replaced if found damaged.
•  Check ratchets movement and do needful adjustment, if required.

Working of Can Washers

Though manufacturers may use special arrangement of treatment for getting effective can washing but certain operational activities as discussed below will result good cleaning:

•  Draining out milk or cream residue before feeding cans in the washing machine preferably over drip saver.
•  Rinse thoroughly with clean, cool water for removing the loosely adhered milk/milk solids layer (Fig. Tank-A).
•  Use warm and high velocity/turbulent detergent water/solution to loose and dislodge materials adhered to the can (Fig. Tank-B). Drain the solution after an effective period.
•  Rinse with clean warm/cool water by circulation for.desired period (Fig. Tank-C), and/or
•  Follow by a clean, hot rinse by circulating hot water to remove all traces of washing solution (Fig. Tank-D). Drain at the end.
•  Follow by steaming with dry saturated steam to sterilize the surface (Fig. section-E).
•  Follow by treatment with a hot air blast to remove the remaining moisture(section-F of Fig.).

Progressive Cleaning & Sanitization Operations in Can Washer
Straight Through Can washer

The above procedure is usually followed in straight-through can washer and similar process is used in rotary type can washers. However, some changes in the above cycle could be made to suit the specific requirement depending upon the design of container, availability of steam or design features of can washer.

In the simple can washing machine popularly known as can scrubbers, the emptied milk can after draining of milk, is scrubbed with the brushes submerged in detergent solution maintained at 45 to 50OC temperature. Later on the can is rinsed with clean water followed by sterilization in the steaming block.

Types of can Washers and Their Operational Details

Raw milk from producers/suppliers is brought to the chilling center or dairy plant in milk cans. Initially, the cans were only made of aluminium or galvanized mild steel but presently stainless steel or plastic coated cans are also emerging. Cleaning of cans is an important feature of a dairy plant. Small numbers of cans are mostly cleaned manually, whereas it is not practicable in large dairy plant or chilling/collection centers. A large number of cans are used for collection of milk from primary collection centers. Manual cleaning takes lot of time and involves huge manpower.

To cope with a heavy load, machine cleaning is preferred for effective washing and sanitization of cans. Better cleanliness through can washer not only helps in preventing quality deterioration of raw milk by good hygiene of cans, but at the same time, this promotes the mind set of dairy about maintenance of overall hygiene practices in the system. The effect slowly and steadily promotes clean milk production in the milk-shed area.

Economical designs of milk cans are available in the market and can be had depending on the scale of operation and financial capability of organization. Periodical review of cleaning and sanitization effectiveness keeps alarmed about the working of washers for taking preventive maintenance action.

Assessment of Effectiveness of Cleaning and Sanitization

Methods of assessment: The presence of foreign matters on the surface can be detected by either of the following methods:
 

Visual inspection: In large tanks/silo proper light arrangement is made to inspect cleanliness status. Remote places could be inspected by focussing powerful light over the surface.

Touching: Touching the cleaned surface with clean & sanitized fingers shall help in knowing the presence of physical/chemical matters. Detergent residue gives whitish appearance over the fingers, whereas presence of milk fat gives oily impression.

Drop test: When clean water is dropped over the inclined/vertical surface, it gives specific flow pattern depending upon the extent of cleanliness. Excessive water-liner breaks could be observed on improperly cleaned surface.

pH test: The most of detergents are alkaline and their presence after rinsing could be detected by checking the pH of the surface. More than 7pH will indicate presence of traces of detergents.

Indicator test: The presence of detergent could also be noticed by applying phenolphthalein indicator over the cleaned/rinsed surface. The trace of detergent will change the colour of the indicator into pink.The sanitary conditions of the cleaned and sanitized surfaces are assessed by the following methods.

Rinse method: The sterilized surfaces are rinsed with distilled water. The result is presented to know the microbial load as colony per litre of rinse. From the rinse collected, a sample of known quantity is tested for counting the colony and the count is multiplied with the either factors of the rinse quantity. Rinse quantity has two factors, one is the sample quantity and other is the quotient of rinse quantity and sample quantity.

Norms for assessing the effectiveness:
 

Swab method: The sanitized surface is wiped with a clean and sanitized cotton and rinsed with the distilled water of known volume. A representative area is properly wiped and rinse is prepared, which is tested for determining microbial load in terms of colonies present in the sample. Actual quantity present in the known rinse will be calculated to find out colony per 900 sq.cm area.

Norms for assessing the effectiveness:

Always neutralize the effect of chlorine in the sample of rinse water by adding 0.05% of sodium thiosulphate to avoid any lethal effects on the viable microorganism.When quaternary ammonium compounds are used as sanitizing chemicals may be neutralized by adding 0.4% lecithin and 1% Tween 20.

Adinosine-triphosphate (ATP) tests provide an indication of viable micro-organism within few seconds and assess the effectiveness of sanitization. This test is useful in correcting the cleaning/sanitizing process well before the commencement of production.

Important Instructions for Use of Detergents and Sanitizers

Use of “Material Safety Data Sheet (MSDS)”: Every detergent and sanitizer has its specific handling requirement, depending upon their reactive nature to users,handling equipment and surrounding atmosphere. In order to prevent harmful effect and inconveniences, one should read carefully and go with safety instructions about the chemicals and its necessary application techniques. Most preferably, these MSDS should be displayed near the place of use and storage.

Selection of effective chemicals: The washing machines are designed by keeping certain types of detergent/sanitizer characteristics in mind and hence, manufacture’s recommendations must be looked into while selecting the detergent & sanitizers.

Safe storage: Following attention is required for warehousing the chemicals to be used for cleaning and sanitizing.

•  Proper labelling of containers of detergents and sanitizers
•  Specifically earmarked space at safe distance from processing areas to prevent cross-contamination of milk and milk products.
•  Availability of proper chemical handling means like hand gloves, safety shoes etc. in the storage vicinity.
• Adequate training to personnel handling these chemicals.
•  The containers of these chemicals should be placed over pallets of suitable materials like plastic.
•  Enough lights should be provided in the storage area.
•  Proper display of precautions in handling.

Sanitization Methods,Factors and Applications

The aim of sanitization or disinfection in dairy plant is to reduce the number of living microorganisms to a level which is considered safe for dairy processing operation.Usually sanitization does not kill bacterial spores.

 

i. Methods

An effective disinfection/sanitization method requires thorough pre-cleaning. The following sanitization methods are generally used:

Heating by Live steam or hot water: The surface is heated by hot water or steam to inactivate the microorganisms. High temperature will denature protein residues and take them on the surface of equipment so, it is important to remove all debris by initial cleaning. Steam is found highly effective due to high penetration power to reach difficult surfaces. It also takes less time to heat the surface and easy to carry to various places like corners, end places (without use of pump). The high temperature helps in fast drying of equipment surface and achieving extra mileage for reducing water activity. This type of sanitization process requires proper time – temperature combination for better results. The steam is directly exposed to the cleaned surface, whereas hot water is filtered before spraying or circulated over the surface. 

By applying chemical solutions: This method is used where heat sanitizing is not practicable particularly to heat sensitive surfaces/processes. It has been also observed that continual use of a particular sanitizer may lead to the development of resistivity in microorganisms and therefore, it should be changed after some time. Following types of chemicals are used depending upon their suitability.

•  Chlorine & chlorine based products: These are generally used in the form of liquid hypochlorite.
•  Idophors
•  Quaternary Ammonium Compound
•  Amphoteric Surfactants

Application of radiation like Ultra Violet rays: This type of application is getting attention day by day for disinfection of packing machine and materials, air required in the processing for ice-creams manufacture and drying products like peda, kalakand, milk cake etc.

 

ii. Sanitization Effectiveness Factors

Following factors need to be considered while using a sanitizer:

•  The concentration of the chemical sanitizer.
•  The temperature.
•  The contact time required to reduce bacteria to a safe level. The time of surface exposure to disinfectant solution – general wet exposure time of no less than 10 minutes.
•  Condition of surface as sanitizers work best on soil free surfaces.
•  Extent of pre-cleaning. Pre-cleaning removes soil which harbours and protects microbes. Once this protection is removed, microbes are more venerable to chemical sanitizers which can kill or inactivate microbes.

 iii. Sanitizer Application

Application of sanitizers depends upon the method of sanitization and characteristics of sanitizers are discussed below:

•  Flooding: Surfaces requiring sanitization are flooded with sanitizer solutions through circulating solution or dipping the container/machine parts in to the sanitizer solution of desired concentration for desired contact time.
•  Fogging: Fogging of suitable chemicals is done over the place requiring sanitization to inactivate the microorganisms.
•  Spraying: Sanitizer solutions of desired concentration are sprayed over the surface by means of sprayer jets.
•  Effectively exposing the surfaces to the live steam through suitably designed nozzles for killing the microorganisms.
•  Use of radiation for inactivation of microbes. The use of radiation waves placed suitably creates sanitization effect in the close vicinity.

Cleaning Methods and Considerations

i. Methods

The following methods may be employed for cleaning of dairy equipment and containers:

Manual Cleaning: It is the removal of soil by scrubbing manually with detergent solution followed by water rinsing.

In-place cleaning: In-place cleaning is most popularly known as C.I.P.( Cleaning-in-place).It is the cleaning of equipment including that of pipe lines, with water and detergent solution without dismantling. A minimum fluid velocity of 1.5 meter per second with turbulent flow is required for effective cleaning of pipelines. Wherever possible, parts of equipments which can’t be satisfactorily cleaned by this method should be identified and should be dismantled and cleaned manually to prevent the possible build up of contaminants.

Low pressure high volume spray: In this method of cleaning, water and/or detergent solution is applied in large volume at pressures up to approximately 6.8 bar or Kg/sq.cm. (100 psi).

High pressure low volume spray: It is the application of water and/or detergent solution in low volume at high pressure, i.e. up to 68 bar or Kg/sq.cm (1,000 psi).

Foam cleaning: Detergent solution in the form of foam is applied and remained in contact for 15-20 minutes over the surface and then it is rinsed off with a water spray.

Washing machines: There are containers like milk cans, crates and bottles etc.,which are commonly used, in the dairy industry. The large in number and smaller in sizes make manual cleaning of these items quite expensive, labour oriented,tiresome and involving huge manpower. These containers could be easily and effectively cleaned by special designed washing machines. The machine performs cleaning procedures as above with the addition of disinfection by hot water rinse at the completion of the cleaning cycle.

In dairy plants following type of washing machines are used:a) can washer, b) bottle washer, and c) crate washer

In all type of washing machines, the cleaning method incorporates rinsing, application of detergent, washing and rinsing with water followed by sterilization with steam/hot water or chemical sanitizers. The solutions are applied by soaking or jet arrangements.

  

ii. Considerations for effective cleaning and sanitization 

 

Milk handling and processing equipments are normally fabricated from highly corrosion resistant materials like stainless steel to provide very good hygienic conditions.Cleaning and sanitization process, by the use of proper system, chemicals and cleaning parameters, should support this feature. In this context, some of the aspects are discussed below:

a) Soap or detergent solutions of effective concentration remove soilings like grease and dirt due to their good wetting and penetrating capabilities and hold them in suspension. Thorough washing with a water rinse is followed by complete drying
.
b) Neutral or general purpose detergents of pH between 7 to 9 are useful for light to moderate heavy foaming type cleanings. These detergents foam well in water and are safe to use on most surfaces.

c) Removal of tightly deposited milk solids/milk stone, atmospheric stains, oils/grease and other light discoloration is carried out with alkaline detergent solutions without using much manual scrubbing. Strong alkaline solutions may be useful in cleaning of heavy greased surfaces. Weak alkaline cleaning agents can be used on most surfaces, however care should be taken to ensure they do not damage the surface.

d) Removal of water scale and milk stone is usually done by acid type detergent solutions, having pH less than 7. Acid detergents are used specially for the removal of mineral scale from metal surfaces of dishwashers and hot water runs.

e) Abrasive cleaning processes use grains/granules, available in the form of a paste, cream or powder, to remove soiling from the hard surfaces. However,use of ordinary steel wool or brushes should be avoided to save surface from damage. As far as possible, spongy or soft fibrous materials like cloth pads should be used.

f) For cleaning of newly installed equipment, soldering flux should be first neutralized with a 5-10% sodium carbonate solution or ammonia water and then, rinsed or washed and dried.

g) Prolonged contact of sanitizers containing chlorine, iodine etc. should be avoided to prevent rusting of surfaces.

h) Stain spots caused due to excessive heating should be removed by scouring with powder.

Cleaning and Sanitization

Definition: Cleaning is the process in which unwanted matters including food poisoning and spoilage microorganisms are removed to prevent contamination of products. Sanitization reduces the microbial load of cleaned surface to a level,which is considered to be safe for handling and processing of dairy and food products. Cleaning without sanitization is meaningless. Both terms are complementary and supplementary to each other.

Unwanted matter or soil: It consists mainly of milk or milk products residues which may be some what altered by processing or by interaction with water,cleaning materials, dust and dirt.

Milk stone: It is the deposition of milk solids, water hardness compounds and washing solutions on the surface due to heating. It normally consists of precipitated,coagulated and heat dried milk proteins and insoluble calcium salts from water and detergent solutions.

 

i. Clean Surface

• Cleaning should result in a clean surface, which may be characterized by:
•  free from visible film or soil,
•  non-emittance of any objectionable odour,
•  non-greasy or rough feeling,
•  non-discolouration of a new white facial tissue wiped several times over the surface,
•  not showing any signs of excessive water break while water is draining it, and
•  not contaminating food products in contact with it.

 

ii. Cleaning Schedule

For effective hygiene program, there should be properly planned cleaning schedule,which should include:

•   cleaning and disinfection of the equipment/tool used for cleaning;
•  allocate responsibility to a person(s) for cleaning tasks;
•  detail necessary safety precautions for the use of detergent and disinfectants;and
•  cleaning procedures that have been designed to meet the particular needs of the process and product concerned
• provision for adequate supervision by management to ensure compliance to procedures

 

iii. Standards and Steps

There are two standards of cleanliness used in the

•  Visual cleanliness: This refers to removal of gross debris (dirt, grime and surface residues) from a surface. Detergents and water are used for the cleaning.
•  Microbial cleanliness: This relates to microscopic cleaning to achieve a low bacterial count i.e. reduce bacteria to a safe level. Chemical sanitizers and/or very hot water/steam is used for this purpose.

There are basically four procedural steps in cleaning and sanitization:

•  Removal of gross debris by brushing, vacuuming, scraping of deposits or other methods whatever necessary, followed by the application of water.
•  The temperature of water used will depend upon the type of soil to be removed and surface to be cleaned.
•  Application of detergent solution to loose the soil and bacterial film and hold them there in solution or suspension.
•  Rinsing with water to remove loosened soil and residues of detergent.
•  Disinfection of the surface.

Methods of Cleaning and Sanitization

The equipment and containers are desired to be physically clean, dry, smooth surface and free from dirt and unsafe bacterial load to prevent occurrence of any sort of food and health hazard in milk and its products during handling and processing.Execution of cleaning and sanitization by using improper methods, material and frequency may result hazardous because of the presence of residual foreign matter,chemicals/ detergents, oil/grease and excessive microbial load in food. The particularity of selection of methods and chemicals depends upon the various considerations like effectiveness, cost, safety in handling, cleaning time, compactness,provision for dismantling and shape/size of equipment/container.

As a standard preparatory step, each and every equipments and container to be used in processing and handling operations need cleaning and sanitization before hand. This is also customary to follow the cleaning & sanitizing after flushing of emptied container/completed process. This reduces cleaning efforts as residues get loosened quickly.

Food hygiene and safety defined, as “all measures necessary to ensure the safety, soundness and wholesomeness of food at all stages from beginning to its final consumption.”

Safe Food may be defines as “a product, which is free of microbial, chemical or physical hazards”

Above definitions inter-relate food hygiene and safety aspects. The food safety is the legal, moral and economic responsibility of manufacturer. It gives a good business by creating reliability and faith in the market. Effective cleaning and sanitization reduce the chances of physical, chemical and microbiological contamination and as such considered to be very essential preliminary process in the dairy plant.

Factors Affecting Efficacy of Sanitizers

i. Physical Factors

Surface Characteristics : All equipment surfaces must be thoroughly clean prior to sanitization. Since the effectiveness of sanitization requires direct contact with the microorganisms, the surface should be free of cracks, pits, or services, which can harbor microorganisms. Surfaces which contain biofilms (films formed by the ability of microorganisms to attach and grow on food and food-contact surfaces under favorable conditions) cannot be effectively sanitized.

Exposure Time : In general, the longer time a sanitizer chemical is in contact with the equipment surface, the more effective the sanitization effect; intimate contact is as important as prolonged contact.

Temperature : Temperature is positively related to microbial destruction by a chemical sanitizer. Owing to the corrosive nature of most chemical sanitizers, high temperatures (about 55° C) should be avoided.

Concentration : Although the activity of a sanitizer increases with the increased concentration in general, it is always best to study the properties of the chemical before using it. Employing sanitizer concentrations above recommendations can be corrosive to equipment and in the long run lead to less cleanliness.

Soil : The presence of organic matter dramatically reduces the activity of sanitizers and may, in fact, totally inactivate them.

 

ii. Chemical Factors

pH : Sanitizers are affected by the pH of the solution. Many chlorine sanitizers,for example, are almost ineffective at pH values above 7.5.

Water properties : Certain detergent residues contain inactivators that react chemically with sanitizers giving rise to non-germicidal products. Thus, it is important that surfaces be rinsed prior to sanitization.

 

iii. Biological Factors

The microbiological load can affect sanitizer activity. The type of microorganisms present can also influence the effectiveness of sanitizer. Sanitizers also vary in their effectiveness against yeasts, mold, fungi and viruses. Certain sanitizers are more active against gram positive than gram-negative microorganisms and vice versa.Spores are more resistant than vegetative cells.

Chemical Sanitizers

The chemical sanitizer, as the name suggests is a chemical substance used at specific conditions to achieve the desired sanitizing effect. An ideal chemical sanitizer should have following characteristics:

•  approved for food contact surface application,
•  inexpensive,
•  low in toxicity and corrosiveness,
•  readily solubilized and possess some detergency,
•  stable under all types of conditions,
•  tolerant of a broad range of environmental conditions,
•  destroy microorganisms rapidly, and
•  have a wide range or scope of activity.

As no available sanitizer meets all of the above criteria, it is important to evaluate the properties, advantages, and disadvantages of available sanitizer for each specific application.The chemical sanitizers used in a dairy are normally used as rinses, sprayed on to surfaces or circulated through equipment in CIP operations. Their major groups are discussed below.

 

i. Chlorine and its compounds

Chlorine, in its various forms, is the most commonly used sanitizer in any food processing plant. Chlorine compounds that are employed include liquid chlorine,hypochlorites, inorganic and organic chloramines. These are broad-spectrum germicides, which destroy microbes by the following means:

•  acting on microbial membranes
•  having a lethal effect on DNA
•  inhibiting cellular enzymes involved in glucose metabolism and
•  oxidizing cellular protein.

The maximum level of application is 200 ppm available chlorine, but recommended usage levels vary. For hypochlorites, an exposure time of 1 min at a minimum concentration of 50 ppm and a temperature of 24° C are recommended. For each 10° C drop in temperature, double the exposure time is suggested. For chloramines,200 ppm for 1 min is recommended.Chlorine has activity at a low temperature, is relatively cheap and leaves minimal residue or film on surfaces. The activity of chlorine is affected by pH, temperature and organic load. However, chlorine is less affected by water hardness when compared to other sanitizers (especially the quaternary ammonium compounds).

The major disadvantage to chlorine compound is corrosiveness to many metal surfaces (especially at higher temperature). Health and safety concerns can occur due to skin irritation and mucous membrane damage in confined areas. At low pH(below 4.0), deadly Cl2 (mustard gas) can form. In recent years, concerns have also been raised about the role of chlorine in the formation of potential carcinogens and therefore, its use as a disinfectant in drinking water.Chlorine dioxide (ClO2), being more environmental-friendly is currently being considered as a replacement for chlorine. ClO2 has 2.5 times the oxidizing power of chlorine and thus, less chemical (1 to 10 ppm typically) is required. It has the disadvantage of being toxic and hazardous. Its highly concentrated gases can be
explosive at risks higher than that for chlorine. As ClO2 decomposes readily in the presence of light or at temperatures greater than 50°C, making it on the factory premises rather than procuring it from outside is recommended.The methods of application of chlorine compounds include

•  circulation with 200 ppm for 5 min through pumps and pipelines,
•  immersion in a 200 ppm solution for 5 min,
•  spraying large open vats with 300 ppm solutions for 5min contact time,
•  fogging closed vats and tankers with 500 ppm solutions with atomizing devices, and
•  brushing cheese vat surfaces, agitators, weighing vats and similar open vessels with 400 ppm solution.

 

ii. Iodine and its derivatives

Iodine has been used as an antimicrobial agent since the 1800s. It is normally marketed in combination with a surfactant as a carrier. These mixtures are termed as iodophors. Generally recommended usage for iodophors is 12.5 to 25 ppm for 1 min. The antibacterial activity of iodine is dependent on

It is generally thought that the bactericidal activity of iodine is due to

•  cell wall damage,
•  destruction of microbial enzyme activity, and
•  direct halogenation of proteins.

Iodophors, like chlorine compounds have a very broad spectrum of activity, being active against bacteria, viruses, yeasts, molds, fungi and protozoa. As iodine is highly temperature-dependent (vaporizes at 49° C), it is suitable for lower temperature applications. The most active, but less stable form is the dissociated free iodine,prevalent at low pH. The amount of dissociation from the surfactant depends on the type of surfactant. The degree to which iodophors are effective depends on properties of the surfactant used in the formulation. Iodine has limited solubility in water. Organic matter and water hardness generally affect iodophors less than chlorine. Although iodine has been used since long in treating wounds, ingestion of iodine gas involves the risk of toxicity in closed environments. Iodine also leads to staining on some surfaces (especially plastics).

 

iii. Quaternary Ammonium Compounds (QACs)

Quaternary ammonium compounds (QACs) are a class of compounds, which are used widely in dairy and food sanitation operations. Since QACs are positively charged cations, their mode of action is related to their attraction to negatively charged materials such as bacterial proteins. It is generally accepted that the mode of action is at the membrane function.These are non-irritant to skin and possess antibacterial and surfactant properties.They should be used with soft water. They are active and stable over a broad temperature range. QACs generally have higher activity at alkaline pH. QACs form deposits that are hard to remove on rinsing glass surfaces. An advantage of QACs in some applications is that they leave a residual antimicrobial film. However,this would be a disadvantage in operations such as cultured dairy products and cheeses, where microbial starter cultures are used.Many QAC formulations can cause foaming problems in CIP applications. Under recommended usage and precautions, QACs pose little toxicity or safety risks.Thus, they are in common use as environmental fogs and as room deodorizers.However care should be exercised in handling concentrated solutions or use as environmental fogging agents.

 

iv. Acid Anionic Sanitizers

These formulations include an inorganic acid plus a surfactant, and are often used for the dual function of acid rinse and sanitization. Unlike QACs, they are negatively charged. Their activity is moderately affected by water hardness. Their low use pH, detergency, stability, low odor potential, and non-corrosiveness make them highly desirable in some applications. Disadvantages include relatively high cost, a closely defined pH range of activity (pH 2 to 3), low activity on molds and yeasts,excessive foaming in CIP systems and incompatibility with cationic surfactant detergents.

 

v. Fatty Acid Sanitizers

Fatty acid or carboxylic acid sanitizers have been in use since the 1980s. Typical formulations include fatty acids plus other acids such as phosphoric or organic acids. These agents also have the dual function of acid rinse and sanitization. The major advantage these offer over anionic-acid sanitizers is lower foaming potential.Fatty acid sanitizers have a broad range of activity, are highly stable in dilute form,are stable to organic matter and also to high temperature applications. They have low activity above pH 3.5-4.0, are not very effective against yeasts and molds and some formulations lose activity at temperatures below 10° C. They are corrosive to soft metals and can degrade certain plastics and rubber.

Radiation

Radiation is a non-conventional form of sanitizers used in the dairy where heat sensitive parts are to be sanitized. Radiation in the form of ultra violet (UV), high-energy cathode or gamma rays rapidly destroys microorganisms. UV radiations may be used on surfaces such as flexible packing materials for contact time in excess of 2 minutes to effectively destroy microbes.

sanitation in Dairy Plants

Sanitizers are used as a part of the cleaning process, to reduce the load of microbial contaminants that may be present on milk/food contact surfaces. Most dairy sanitizers,when used appropriately, destroy a broad spectrum of microorganisms. Sanitation procedures should be performed after washing and immediately before processing.Most chemical sanitizers are inactivated by organic matter and are, therefore,ineffective on poorly cleaned surfaces. Dairy sanitizers should be non-toxic, non-corrosive, quick acting, be easily applied and economic. Sanitizers commonly used in the dairy industry may be classified as 1) thermal 2) radiation or 3) chemical Sanitizers.

 

 i. Thermal Sanitizers

The effectiveness of thermal sanitizing depends on a number of factors including:microbial contamination load, humidity, pH, temperature and time.

Steam: The use of steam as sanitizer has limited application, as it is relatively expensive. It is also difficult to regulate and monitor contact temperature and time.Besides these, the by-products of steam condensation may hamper cleaning operations.

Hot Water: This is commonly used in many dairy plants. It involves circulating water of at least 77° C (determined at the outlet) for at least 5 minutes. Applying higher temperatures (>85° C) for longer times (10-15 minutes) are recommended to allow heat penetration into areas that are hard to reach. Hot water treatments should be followed by a cooling chemical sanitizer rinse. Hot water will often provide greater destruction and longer milk shelf-life than can be achieved with chemical sanitizers alone.

The main advantages of hot-water sanitization are as follow:

•  easy to apply,
•  penetrates into cracks and crevices,
•  readily available,
•  relatively inexpensive,
•  relatively non-corrosive, and
•  very effective over a broad range of microorganisms.

It also has a few limitations, namely:

•  forms films or (or contributes to their formation), thereby shortening the life of equipment or their parts,
•  high-energy costs,
•  safety concerns for employees, and
•  slow process which requires come-up and cool-down time.

Cleaning Agents

The entire class of cleaning compounds may be divided into two groups: a) the alkaline cleaners and b) the acid cleaners in addition to wetting, sequestering agents and surfactants.

 

i. Alkaline Cleaners

This group comprises of the basic alkalis, polyphosphates and the wetting agents.As none of these groups alone can fulfill all the functions of a cleaning agent,blends of their mixtures are generally used.

Basic Alkalis : Basic alkalis, such as soda ash, caustic soda, tri-sodium phosphate and sodium metasilicate are the ingredients in most of the common dairy cleaners.Two or more of them are used in combination as a rule to give the needed properties to the blended product. In addition to providing alkalinity for the cleaning process, they have other properties that affect the cleaning process in various ways. Some of these are detailed below.

a) Caustic soda (Sodium hydroxide, NaOH)

•  High germicidal action
•  Dissolves milk proteins
•  Lacks deflocculating & emulsifying power
•  Most corrosive on hands & metals

b) Soda ash (Sodium carbonate, Na2CO3)

•  Most inexpensive
• Good buffering capacity. The good buffering capacity of soda ash makes it useful in solutions that are used over extended periods, as in hand bottle washing.
•  Poor water softener
•  Only fair deflocculating & emulsifying action
•  Not suitable for hard water. When soda ash is used in hard water, calcium carbonate is precipitated and this pre-cipitate causes hard water spotting and helps develop milk stone deposits on dairy equipment. This may be prevented by using along with soda ash, higher phosphates in quantities large enough to sequester or tie up the water hardness.

c) Trisodium phosphate (Na3PO4)

•  High solubility, deflocculating & emulsifying powers
•  Fairly expensive
•  Fair water softening capacity owing to the flocculent character and insolubility of the calcium and magnesium phosphates formed.
•  Relatively corrosive on tin. Corrosive action can be reduced by adding meta-silicate as a protective agent in the mixture.
•  Limited levels permitted. Concentrations are limited to 0.5 – 1.5% today to minimize phosphate levels in wastewater.

d) Sodium metasilicate (Na2SiO3. 5H2O)

•  High active alkalinity
•  Excellent deflocculating & emulsifying properties
•  Relatively non-corrosive despite strong alkalinity, protects metals from other corroding alkalis
•  Good suspending abilities. Very effective in holding the soil in suspension during the washing operation so that complete cleaning is possible.
• Only a fair water softener. Fair water softening capacity because the calcium and magnesium silicates formed in hard water are floccu-lent and insoluble in solutions.

e) Modified sodas

• These are mixtures of soda ash and sodium bicarbonate. They are useful for manual washing operations, as they do not cause skin irritation.

ii. Acid Cleaners

Acid cleaners are used in dairy plants mostly to remove milk stones. They are also vastly employed in the cleaning of high-temperature processing machines. Equipment such as plate heat exchangers (pasteurizers), tubular heaters etc. are normally cleaned in two phases, the first phase with alkali and in the second phase, with acids. Acid type cleaners are also used in can washing.The acids used in the dairy industry are blends of organic acids, inorganic acids,or acid salts usually with the addition of a suitable wetting agent. To be effective,an acid type detergent at the point of use should be at a pH of 2.5 or below. To be effective, it should work well in hard as well as soft water and should show a minimum of corrosion on dairy metals. The characteristics of acids normally used are listed below.

(i) Inorganic (mineral): muriatic acid, sulfuric acid, nitric acid, phosphoric acid)

•  Corrosive, dangerous to metals
•  High concentrations dangerous to handle
•  Injurious to clothing
•  Irritating to skin
•  Low pH due to high degree of ionization
•  Strong
•  Under certain conditions some inorganic acids will precipitate insoluble salts

(a) Nitric acid (HNO3): This inorganic acid is very good for removing milk stones and hard water scale. Although it attacks tin readily, it is suitable for aluminium and stainless steel (SS). Nitric acid is hazardous on the skin. It is widely used at strengths of 60% in automatic cleaning of plants (CIP – Cleaning-in-Place).

(b) Phosphoric acid (H3PO4): This is a mildly strong acid that replaces nitric acid in many dairy cleaning operations.

(ii) Organic (generally vegetable acids): acetic acid, lactic acid, hydroxyacetic acid, citric acid, levulinic acid, tartaric acid)

• Acid reaction tends to prevent and remove deposits of calcium and magnesium salts derived from either milk or water
•  Can be combined with wetting agents, hence penetration
•  Mild, stable, less corrosive
•  Safe, gentle, harmless to hands in use-dilutions

  iii. Wetting Agents

Water and most other aqueous solutions wet metal surfaces with difficulty unless these surfaces are free from fats and oils. Wetting or surface acting agents thus help to improve the wetting of surfaces. They also aid in penetration of the solution into capillary pores and minute spaces between the equipment surface and soil particles. The three groups of surfactant solutions are anionic (e.g. sulphosoaps,sulphated alcohols, alkyl aryl sulphonates), non-ionic (e.g. condensation products between ethylene oxide and an alkyl phenol) and cationic (e.g. quaternary ammonium compounds - QACs). Even at concentrations as low as 0.15% they reduce the surface tension of water to half. Increasing the concentration does not affect the degree of lowering of surface tension, and therefore, the amounts used in cleaners are usually small.

 

iv. Sequestering Agents

Sequestering and chelating agents prevent precipitation of salts formed due to hardness of water. There are three main classes of such agents.

a) Ethylene diamine tetra-acetic acid (EDTA) or its sodium salts

•  Heat stable
•  Compatible with Quarternary Ammonium Compounds (QACs)
•  Bacteriostatic property
•  Prevents redeposition

b) Sodium salts of gluconic and heptonic acids

•  Stronger than EDTA in chelating action of Ca and Mg
•  Requires high concentration of NaOH (~ 2.5%) for effectiveness

c) Polyphosphates (sodium tripolyphosphate, sodium pyrophosphate)

• Not heat stable
•  Limited levels permitted. Environmental regulations limiting the levels of phosphates in waste waters, many cleaning compounds have removed or reduced phosphates, using chelating agents to eliminate the effects of water hardness. Concentrations may be limited to 0.5 to 1.5%.

  v. Enzymes

Proteolytic enzymes are utilized, generally in combination with alkali and surfactants to increase the cleaning efficiency of equipment heavily soiled with protein.They have been especially useful in the cleaning of membrane processing plants.Lipases have been used also in a few cases to improve the removal of fat from surfaces.

 

vi. Chlorine

Chlorine increases the effectiveness of alkaline components tremendously (50-200/ml chlorine increases the peptizing efficiency). As removal of protein films lessens the development of mineral milk stone deposits, it also reduces the build--up of mineral deposits. Chlorinated trisodium phosphate, hypochlorides and chloro-isocuranic are the commonly utilized chlorine compounds. The chlorine compound has to be compatible with the alkaline reagent, or else, it will result in the development of white deposits upon the equipment. Chlorinated alkalis do not function as bactericidal agents because of their high pH. The high pH also minimizes the corrosive activity of the chlorine component.

 

vii. Inhibitors and Antifoaming Agents

Inhibitors such as sodium sulphite are used to minimize the effect of acids and alkalis on metals. Sodium sulphite protects tinned surfaces, whereas sodium silicates protect aluminium and its alloys from mild alkalis. Antifoaming agents reduce the  foam in detergent solutions. This, in turn, decreases the need for water.

Cleaning Process

i. Steps Involved

The modern cleaning agents used in a food processing plant are complex combinations of chemicals mixed in order to achieve specific functions. Four fundamental steps involved in any cleaning process are:

• Dislocating the solid and liquid soils from the surface to be cleaned by saponifying the fat, peptizing the proteins and dissolving the minerals;
   Scattering the soil in the solvent by dispersion, deflocculation or emulsification; and
•  Preventing re-deposition of the dispersed soil back onto the clean surface by providing good rinsing properties.
• Bringing the detergent solution into close contact with the soil to be removed by means of good wetting and penetrating properties;

ii. Qualities of a Good Detergent

In addition to achieving these essential steps, a good cleaner should:

•  Soften the water adequately;
•  Dissolve quickly and completely;
•  Be non-corrosive;
•  Be non-toxic;
•  Be economical
•  Remain stable upon storage and
•  Be non-caking and non-dusting.

It is obvious that no single chemical can satisfy all these criteria. Therefore, a cleaning solution is generally made up of several ingredients, each one having one or more of these properties. The selection of the compounds to be blended into a good cleaner requires highly specialized knowledge. The different ingredients of cleaning compounds are combined in such a manner so as to assure the following functions:

Deflocculation: Breaking up of soil flocs on surfaces to improve removal of the soil.

Dispersion: The power to scatter and flocculate so that mineral films are not redeposited on the surface from which they are removed.

Dissolving: The ability to dissolve both inorganic and/or organic solids so as to speed their transfer into solution.Emulsifying,

suspending: The power to emulsify fat and suspend other solids in solutions.

Peptizing power: The ability to attack and disperse protein by hydrolyzing it.

Rinsing power: The ability to separate dirt/soil from the surface to which it has been adhering when fresh water is flushed over the surface.

Saponifying power: The capacity to turn fats into soaps.

Sequestering: The ability to prevent deposition of undesirable mineral salts on surfaces being cleaned.

Wetting: The capacity to lower the surface tension of the water medium so as to increase its ability to penetrate soil/dirt.

 

iii. Classification of Detergents

The chemicals used as cleaning compounds can be grouped into five basic classes:Alkalis, complex (or poly) phosphates, surfactants, chelating compounds and acids.Their general functions are listed in below  Table 

Classification of cleaning compounds and their major functions

The different classes of cleaning compounds vary in the efficiency of their actions,as listed in Table

Relative efficiency of the different classes of cleaning compounds