Cleaning and Sanitizing of Containers and Equipment

"The product contact surfaces of all multi-use containers, utensils, and equipment used in the transportation, processing, handling, and storage of milk or milk products shall be effectively cleaned and shall be sanitized before each use. Provided, that piping, equipment and containers used to process, conduct or package aseptically processed milk and milk products beyond the final heat treatment process shall be sterilized before any aseptically processed milk or milk product is packaged and shall be re-sterilized whenever any unsterile product has contaminated it."


This item requires that all milk contact surfaces be effectively cleaned and sanitized before each use. The only exception to this is the Ordinance provision that milk storage tanks be emptied and cleaned at least every 72 hours and raw milk and heat treated milk storage tanks use to store products longer than 24 hours and all raw milk silo tanks be equipped with a 7-day temperature recording device.

This recorder shall have a scale span of not less than 50 F, be accurate to plus or minus 2 F, include the normal storage temperatures plus and minus 5 F, with 2 F minimum scale divisions not less than 0.040 inch apart and time scale divisions of not more than 1 hour. The recording chart of these devices must be capable of recording temperatures up to 180 F.

Computer generated temperature recorders which provide a printout which is readily discernible and meets the intent of the Ordinance are acceptable as are devices equipped with multiple sensors or recording pens.

Records are a significant part of the cleaning and sanitizing process. All CIP charts are to be retained by the plant for a minimum of three (3) months. This includes records for cleaning and sanitizing of all plant product processing equipment.

It is also recommended that log records are maintained of manual cleaning operations. This will enable plant quality control staff and the regulatory agency to validate plant cleaning/sanitizing operations.

The Ordinance requires that the regulatory agency review and initial CIP charts during each inspection.

Milk tank trucks shall be tagged or log book records maintained to verify each time the tanker is cleaned and sanitized. The wash tags shall only be removed at the plant or receiving station where the tanker is next cleaned and sanitized. These records shall be retained for 15 days for regulatory review.

Note: Cultured product storage/processing vessels may not have to meet the 24 hour emptying and cleaning requirements if their process demands extended periods of storage, however, a plant should package cultured product within 24 hours of breaking the curd.

Note: Cultured product storage/processing vessels may not have to meet the 24 hour emptying and cleaning requirements if their process demands extended periods of storage, however, a plant should package cultured product within 24 hours of breaking the curd.

Recent changes in the PMO permit the restricted use of condensing water from milk evaporators and water reclaimed from milk or milk products as follows:

  1. Pre-rinsing of the product surfaces where pre-rinses will not be used in food products, and
  2. Cleaning solution make-up water; provided that for EITHER USE, ITEMS #3-11 OF APPENDIX D, V OF THE PMO 1 ARE MET..AND..
    • There is no carry-over water from one day to the next OR,
    • The temperature of all water in the storage and distribution system is maintained at 63o C (145o F) or higher by automatic means, or
    • The water is treated with a suitable, approved chemical to suppress bacterial growth by automatic methods prior to entering the storage tank, AND
    • Distribution lines and hose stations are clearly identified as "limited use reclaimed water", AND
    • Water handling practices and guidelines are clearly described and prominently displayed at appropriate locations within the plant, AND
    • These water lines are not permanently connected to product vessels, without a break to the atmosphere and sufficient automatic controls, to prevent the inadvertent addition of this water to product streams. NOTE: Recovered water may be used as boiler feedwater for boilers not used for generating culinary steam or in a thick, double walled, enclosed heat exchanger.
  3. Appendix D, V requires in Items 3 - 11, among other things a turbidity meter, chemical OD test, monitoring devices too automatically divert, organoleptic quality including weekly samples and records, allows addition of approved bacterial suppressants, and adequately constructed and protected storage vessels.

CLEAN-IN-PLACE (CIP) The recommended steps in a clean in place (CIP) operation may involve the following:

  1. Remove those items that require manual cleaning such as fill tubes, manhole gaskets, plug valves, etc.
  2. Provide physical breaks between any circuits or tanks containing product.
  3. Pre-rinse or flush thoroughly with cool water not to exceed 80oF.
  4. Discard pre-rinse water, flushing until relatively clear.
  5. Circulate an effective detergent solution throughout the circuit for the period of time necessary to remove the residues in the circuit.
  6. Circulate a rinsing water.
  7. Circulate an acid detergent when needed followed by another rinse.
  8. Sanitize immediately before use.

Most modern plants have installed clean-in-place systems throughout the plant. Prior to this, plants cleaned all their processing equipment, including tanks, vats, pumps and lines manually which involved complete disassembly, manually brushing with a cleaning solution, rinsing, reassembly and finally sanitizing. This was of course all highly labor intensive.

In the early 1950's, companies such as Tri-Clover, Cherry-Burrell, and Alloy Products Corporation developed special CIP joint/gasket assemblies which were conducive to CIP methods.

In the mid 1960's, clean in place systems led to the use of all-welded product piping systems, automatic (air operated) valving systems, large milk storage tanks or silos designed to be cleaned mechanically, and the installation of properly supported and self draining product lines (recommended minimum of 1/16 inch per foot slope).

The process of circulation cleaning, which was first applied in the dairy industry in the 1940's, involves the continuous pumping of rinse (and often times pre-rinse) and wash solutions throughout the milk product circuits for the purpose of the removal of milk and milk residues rendering the inner surface clean to sight and smell.

Now however, there may be separate CIP circuits for different processes, product lines, or product integrities. (raw vs.. pasteurized) and many plants have installed modern computer controls to monitor their cleaning processes.

The CIP cycle begins at the "make-up" tank containing either a clean water rinse or dairy detergent wash solution. Both chlorinated alkaline and "hot acid" cleaners or caustics are used in the cleaning solution.

The solution is circulated by using relatively higher velocity pumps capable of circulating the solution throughout the circuit, then returning it to the cleaning reservoir.

Systems are monitored for temperature which is required under the Ordinance. Many modern systems also are monitoring , controlling and recording the levels of, pH concentration of cleaning detergent and sometimes flow rates.

Temperatures shall be measured and recorded in the return solution line near the make up tank, however other means of measuring, monitoring, and recording CIP solutions may be used if reviewed by the FDA and found acceptable by the local regulatory agency.

Product storage tanks (except silo tanks) cleaned using circulation from the tank outlet through a pump which returns the solution to the tank spray ball would not have to be equipped with a recorder, providing there are no product lines or other attached CIP circuits involved.

Special attention must be given to the adequate venting of large milk storage tanks including milk silo tanks.

One process engineer has stated that the provision of two, unobstructed three inch openings will adequately vent any tank (horizontal or vertical) using temperatures of <150o F. This is not a hard and fast rule but can be used as a guideline in considering adequate venting of CIP operations for tanks.

Before beginning a CIP of larger tanks and silos, the proper CIP venting door device should be installed in the manhole opening to provide adequate space for air movement resulting from extreme differentials in temperatures.

The basic components of any CIP system will include the following:

  1. Permanently installed product piping and air operated valves
  2. CIP solution make-up tanks
  3. CIP pumps
  4. CIP supply and return solution piping
  5. Spray devices(either permanently mounted or drop- type)
  6. Solution collection manifolds
  7. Chemical feed systems and equipment
  8. The CIP control/monitoring systems and necessary recorders. CIP temperature recorders must meet all requirements as listed in Appendix H, page 207 of the Ordinance.


Water hardness is the term applied to water supplies characterized by either a high mineral content, usually high in calcium or magnesium bicarbonates, or magnesium chlorides, and sulfates. Generally water hardness is precipitated by most alkaline materials but not by heat.

Some plants may need to condition their water by either selecting the proper detergents or in more severe hard water cases may need to install ion exchangers to remedy the problem.

Water over 100ppm hardness apply in the latter cases and usually softeners are required for boiler water or cooling tower feed water supplies.

The 3-A Accepted Practices for Permanently Installed Sanitary Product Pipelines and Cleaning Systems require that "All connections between the solutions circuit and the product circuit shall be constructed as to positively prevent the commingling of the product and solution during processing".

Cleaning efficiencies may be enhanced by introducing pressurized air into the system and most systems are fitted with a method to eliminate entrapped air.

Some systems are designed to recover sanitizing solutions for use as a system pre-rinse on the following CIP cycle.

Vertical or silo tanks are cleaned not by sprays but rely on introduction of the cleaning solution at the top of the tank onto a diversion disc or plate which deflects the solution to make contact with the interior tank surfaces.

Also, the tank must be so fabricated and installed to be self draining and to have a fast flushing action across the bottom of the tank.

No matter how sophisticated the CIP system may be, there will always be a need to clean those portions of the equipment not exposed to the cleaning process. Examples of this would be the agitator paddles in silo tanks, air blow fittings, plug type valves, tank venting devices, etc.

Clean Out of Place (COP)

This is the term used for those cleaning operations involving the removal of small sections of piping, valve parts, filler parts, and other small appurtenances that are not normally cleaned in place and placing them into a cleaning vat. The vat is equipped with a heat source, adequate dairy cleaner or caustic, normally steam injection, and a recirculating pump. Recording devices are not required on these units, although many plants have installed them to provide cleaning records as a part of their overall quality program.

Manual Cleaning Operations

Regardless of the automation and engineering built into a plants operation, there is usually a need to manually clean the contact surfaces of the many small parts used in a normal days operation.

This may include filler parts, valves, filler surfaces (mandrels, shields, guides, etc.), small vats, cultured product packaging equipment appurtenances, tanker pumps, fittings, and valves, culture room product handling utensils and equipment (processing vats, curd cutting knives, whey drainers, steam cookers, curd movers and stirrers, etc.).

Manually washed fillers require hand brush washing of the filler bowl, gaskets, the product supply line, ells, and bushings.

Since brushes are used in manual washing operations, they must be of the non-absorbent, nylon or plastic bristled type and designed to not retain soil (not recommended to use hollow body or handled type) and be quick to dry. Brush integrity must be maintained so that brushes used for floor drains or similar surfaces are not used on contact surfaces. This may be accomplished by color coding, marking, etc.

Utensils should be cleaned using a two compartment wash and rinse sink. Sanitizing with chemicals must be accomplished using a third treatment vat, unless heat is used for sanitizing.

The use of absorbent items, such as rags and sponges should be eliminated to reduce the potential of spreading microorganisms throughout the plant environment.

Separate brushes should be used for product and not-product surfaces and the use of wooden handled brushes, tools, paddles, etc. should not be used in production areas.

Particular attention must be given to cleaning underneath gaskets, "o-rings", and other small orifices in which residue and bacteria may accumulate.

Special emphasis should be given to the following when evaluating the effective cleaning of milk contact surfaces:

  • AUP air blow devices/fittings;
  • Storage tank agitator blades, shafts, fill inlets, vents, gaskets, shaft "O" rings;
  • Filler valves, tanks, small parts (springs, screens, gaskets and "O" rings, vents, drain valve and lines, underside of shielding,);
  • Plug valves, "butterfly valves";
  • Fruit feed pumps, (varigators), fruit pumps;
  • Homogenizer stand pipes;
  • Reclaimed product surge tanks, milk cans, lines;
  • Silo manhole doors (inside surfaces, sampling cocks, tank surface on inside below door opening);
  • Silo vent caps (mold, slime);
  • Liquefier (powder mixing tanks) outlet valve and connecting piping;
  • Raw receiving lines and fittings;
  • Product pumps ("O" rings, back plates, covers);
  • Filter housings, springs, gaskets in raw receiving area;
  • Air eliminators in receiving areas, air "burps" on product and CIP lines;
  • Pasteurizer regenerator plates (points of greatest temperature differential);
  • vacuum breakers, single stem flow diversion valves;
  • Tank fill goose necks; and In-door sample valves.



Used to neutralize, break-up, and suspend soil in the cleaning solution. Alkalines have been termed the "guts" of the dairy cleaners and are usually termed generically as "caustics" and or alkaline chlorinated cleaners.. Chemically they are sodium hydroxide (NaOH, OR CAUSTIC SODA), potassium hydroxide (caustic potash), sodium carbonate (soda ash) or sodium hypochloride (NaOCL) and sodium silicates and have a pH higher than 7. They attack the fat and protein residues on all types of dairy processing equipment.

They are generally combined with a water conditioning additive such as liquid phosphate under hard water conditions and usually contain surfactants or wetting agents which enhances the cleaning action.

The water properties must be considered, since most cleaning solutions are made up of 99% water and the amount of neutralizers used should be customized to meet the individual demands. These detergents condition the water to prevent scum formation, and help to prevent saponification (the chemical reaction which converts the actions of alkali and fats into soap and glycerin) during the cleaning cycle.

Most alkaline detergents contain chlorine which also breaks down the fats and proteins.


Acid detergents are those with a pH of lower than 7 and react with mineral deposits which have accumulated on milk contact surfaces. These acid cleaners may contain either nitric, phosphoric or a mixture of both acids; however phosphoric acid based cleaners are the most widely used in the U.S.

Milk and water mineral deposits (termed milk stone) become hardened and layered on the equipment surfaces and provide excellent surfaces on which "biofilms", which are adherent macro-colonies of bacteria, may thrive. Milk stone may consist of milk solids, calcium, magnesium, iron, sulfates, etc.

Acid based detergents (or rinses) do not saponify. They do, however, tend to neutralize any alkalinity and react with the milk minerals which are then carried away in the rinse cycles. Acid rinses will usually provide a bacteriostatic condition, however the equipment must be effectively cleaned with an chlorinated alkaline based detergent prior to using the acid rinse.

Using an acid detergent without first removing the fats and proteins with a chlorinated alkaline detergent will result in fixing the protein soil to the surface. Acid rinses may also tend to protect against corrosion and when used in proper strengths will not attack rubber parts.

MILKSTONE White to yellow Minerals from milk Acid wash Regular and proper cleaning procedures coupled w/ acidified rinse FAT/ GREASE Hanging water droplets Greasy (white) appearance 1. Low water temperatures 2. Improper detergent concentration 3. Regular use of acids in place of alkaline detergent 1. Proper water temperature 2. Correct concentration of alkaline detergent Regular and proper cleaning procedures coupled w/ acidified rinse MINERAL (Calcium, Magnesium) White (water- stone) chalky to gray 1. Rinse too hot, drop-out of minerals from water supply 2. Failure to use acid detergents 3. No acidified rinse 4. Alkaline detergent used cannot handle hard water at present concentration Acid wash 1. Acid wash 2. Alkaline detergent used has good water conditioning 3. Water softener or treatment
Residue Description / Appearance Cause Removal Prevention
PROTEIN Blue rainbow hue varnish like, "apple sauce" 1. Using non-chlorinated cleaner
2. Inadequate pre-rinse
3. Improper cleaning
Chlorinated alkaline detergent 1. Adequate pre-rinse
2. Proper cleaning w/ proper use dilution after each usage
3. Chlorinated alkaline detergent


The following is a list of terms commonly used when referring to the properties of detergents used in the food industry.

  1. Emulsification - The spontaneous dispersion of substances (proteins, gross soil particles, etc.) when brought in contact with water.
  2. Peptize - The mechanical action combined with a surfactant which results in two immiscible liquids to form a stabilized colloid.
  3. Saponification - The combination of fatty acids and oils with alkali to produce soap.
  4. Sequestering and Chelating - The prevention of precipitation of hard water constituents by keeping them in suspension as stable and solid compounds.
  5. Wetting - Lowering of surface tension which permits cleaners to break the bond between the soil and surfaces.

The Ordinance requires that cleaned milk contact surfaces of equipment be sanitized before each use and that aseptic processing equipment shall be sterilized before use and re-sanitized or re-sterilized in all instances whenever contaminated.


For our purposes only conventional milk processing sanitizing will be addressed in this section.

All multi-use containers, equipment, and utensils must be sanitized before use. The method of sanitization may be either by chemicals or the heat method.

Adequate sanitization may be accomplished by using one of the methods as described in the following table.

Chemical Sanitizers: General Information

GENERAL INFORMATION - The Code of Federal Regulations (CFR's), Title 21, Part 178, Section 1010, Page 316-323, lists all the acceptable sanitizers available for use in food plants. This section list the chemistry and general guidelines for use for each sanitizer, including the recommended strengths. Federal codes also prohibit the use of any chemical in a strength higher than that recommended to accomplish its intended purpose in an effort to reduce the possibilities of harmful chemical residues in food products.


Chlorine is the most common chemical sanitizing agent used in the milk industry. One of the more common forms of chlorine is sodium hypochlorite which is the soluble salt of hypochlorous acid combined with sodium chloride. This is the stable form of a liquid chlorine solution however has a limited shelf life.

Granular chlorine sanitizers are based upon the salts of an organic carrier which contains releasable chlorine ions. When blended with water, sodium hypochlorite is released and the hypochlorous acid is the active antimicrobial for all chlorine sanitizers.

The killing rate of chlorine is greatly influenced by the pH of the solution. For instance at a solution of 25 ppm chlorine will deactivate organisms at pH 4 in 15 seconds, while a pH level of 10 would take up to 10 minutes. Temperatures of the solution also play an important role in chlorine effectiveness rates. Optimum temperatures of chlorine range from 75o F - 100o F.

Chlorine solutions deactivate the microorganisms by affecting the cell wall transport mechanisms, causing the formation of chloramines with the amino acids of proteins. This denatures the proteins within the enzymes causing intracellular damage and destroys the microbe.

Chlorine sanitizers are generally used in recirculated cleaning systems for cleaning small parts, milk tank trucks and environmental surfaces.


Iodine sanitizers used in milk plants are usually in the form of iodophors. Iodophors are simply iodine which are combined with non-ionic wetting agents (surfactants). Iodophors, when diluted for use in the proper concentrations, have a low pH value (pH 2.6 - 5.0) which enhances their germicidal qualities. This along with increased temperatures (up to 120o F) makes them a popular sanitizer for use in milk plants.

Iodine interferes with the intracellular protein in a similar manner to that of chlorine, with the sulfhydryl, amino or carbonyl protein groups being affected.

Iodine sanitizers are used extensively in filling/packaging machines and areas, culture processing equipment, drop hoses and hand dipping stations.


These sanitizer agents are commonly known as "Quats" and are highly effective in the denaturing of cell (bacteria) proteins which leads to their destruction.

Bacterial cells walls are electrically charged and can possess a net positive or negative charge largely depending on the acidity of the solution in which they are found. Moreover, each type of bacteria have a different cell wall composition. Generally bacteria grow in the optimum pH range of 6.0 to 8.0, and are generally negatively charged at this growth range. The cationic sanitizer, having a positive charge, attracting their opposite charge (negative). This interaction between the opposite charges tends to produce drastic effects upon the cell wall and will cause fluid leakage and eventually cellular rupture. In concentrations of 50 -100 ppm cationic surfactants will not only denature the cells proteins, but also totally inactivate the enzyme and actually alter the cell wall permeability.

Quats are generally used in case washing areas and other environmental surfaces, but are rarely used in CIP and plant equipment sanitization where culture processes may be damaged.


This chemical sanitizer has become more widely used in the dairy industry, predominately in the sanitizing of environmental surfaces of equipment, floor drains, and other areas to greatly reduce the microbial load in these area. Recommended (CFR) effective uses of this sanitizer for contact surfaces must not exceed 200ppm and a recommended strength of 100-200ppm has been established. The CFR describes the formulation for this sanitizer by either metering a concentrated chlorine dioxide solution into potable water or by acidification of an aqueous alkaline solution of the oxychloro species.


Aqueous solutions containing one or several of the acceptable acid sanitizers has been effective in the deactivation of microbes. The active acid ingredient may be sulfonic, phosphoric, de-cationic, cyanuric or a blend of the above to provide not more than 100ppm of available halogen.

Note: Trichoromelamine based sanitizers are not approved for use on milk contact surfaces.

Acid sanitizers are used primarily for large (silo) milk storage tanks, milk tankers and other large milk storage vessels within the plant.


"After cleaning, all multi-use milk or milk product containers, utensils, and equipment shall be transported and stored to assure complete drainage, and shall be protected from contamination before use".

Once the milk processing equipment has been properly cleaned special care must be taken to prevent contamination prior to the next use. Cleaned equipment and/or utensils must be stored to be protected from splash, dust, insects, overhead dripping, condensation, unnecessary handling, or any other possible source of contamination.

Multi-use utensils, containers and equipment must be stored above the floor on clean racks or other storage devices, inverted for protection and drainage. Care must be taken not to contaminate the clean equipment or utensils by splash from floor, wall or ceiling cleaning operations.

Portable packaging machines must be stored in areas where contamination is less likely, preferable in processing equivalent rooms or acceptable dry storage rooms and should be protected in some manner such as covering with clean plastic sheeting, etc.

Clean equipment must never be stored on dock areas, in machinery areas (boiler or sweet water rooms), or in out-buildings which are not vermin proof or otherwise unsuitable for food processing equipment storage.


  1. Economical
  2. Effective against most bacteria, spores, phages
  3. Readily available in liquid or granular form
  4. Not affected by hard water salts
  5. Test kits available
  1. Corrosive
  2. Effectiveness is pH dependent
  3. Strength dissipates under storage, heat or light
  4. Skin irritant, objectionable odor
  5. Hard on rubber parts
  1. Color indicative of strength
  2. Activity less affected by organics
  3. Effective against wide variety of non-sporeformers
  4. Solution not affected by hard water salts
  5. Not a skin irritant
  6. Stable, long shelf life
  7. Non-corrosive
  8. Test kit available
  1. Effectiveness decreases with increased pH
  2. May discolor equipment
  3. Less effective against spores
  4. Should be used above 120o F.
  5. May cause product off flavors
  1. Active against wide range of organisms, especially gram positive slime-formers, thermodurics
  2. Low toxicity, odorless, colorless
  3. Non-corrosive
  4. Stability excellent
  5. Heat stable, long lasting
  6. Less affected by pH
  7. Non-irritant to skin
  1. Undesirable in cultured dairy product applications
  2. Low activity against gram negative and coliform organisms
  3. Loses effectiveness with anionic detergent contamination.
  1. Non-corrosive
  2. Unaffected by hard water, temperature, or organic contaminants
  3. Rapid activity
  4. Effective on wide range of microbes(thermodurics, phages, and yeasts)
  5. Controls milk-stone
  1. Increase in pH level decreases effectiveness
  2. Cannot be used with alkaline detergents
  3. Is less effective against thermo- durics, spores, psychrophils
  4. Relatively expensive
  5. Leaves foam residual in CIP applications

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