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Dairy processing: Evaluation of dairy processing equipment

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The follow information may assist dairy processors in evaluating the array of equipment they use in their establishments. It provides general guidelines applicable to all dairy equipment as well as additional guidelines for specific types of equipment. Dairy processors can use this in conjunction with their maintenance and sanitation control measures to evaluate equipment and components which may affect the safety of dairy products.

General criteria for evaluating dairy processing equipment

There are two major properties of sanitary equipment design:

  1. Cleanable
  2. Protects the food from contamination

To determine if a piece of equipment is cleanable, evaluate the construction material, accessibility of product contact surfaces and equipment design. The possibility of product contamination due to accumulation of food residues, microorganisms and other contaminants is greatly affected by these factors.

Construction material

Equipment design

The effectiveness of cleaning is dependent on the design. Inadequately rounded corners, sharp angles and dead ends are impediments to good cleaning. Other design features that have the potential for creating spots where food residues can accumulate are the locations of monitoring, control and recording devices. These include thermometer wells, pH probes and sampling ports.

  1. Facilitate cleaning, sanitizing and maintenance.
    • Ensure that the equipment is easily dismantled to allow access to the product contact surfaces for manual cleaning and subsequent inspection
    • Clean enclosed equipment that can't be dismantled by clean-in-place (CIP) methods
      • The use of CIP techniques may reduce the potential for human error that can be associated with manual cleaning.
    • Ensure product contact surfaces:
      • Are self-draining
      • Have no dead ends
      • Are free of impediments to product flow and sites where contamination may build up
      • Are in contact with circulating cleaning solutions
      • Are visible for inspection when assembled or readily disassembled
      • Allows CIP where possible
      • Has adequate space within and around equipment
  2. The piece of equipment protects the food from contamination from outside or within the food equipment.

    Throughout the processing steps, it is necessary to protect the product from environmental and other contaminants. For example, condensate from overhead pipes may drip into an open vat. Covers are installed over tanks, hoppers, flumes, conveyors, and other open equipment to prevent debris from entering the system. Closed systems are best but points where the food enters and exits the system are still vulnerable.

    • Ensure covers are close fitting and have a downward lip
    • Have protection from draining or dripping
    • Ensure there are no open gratings or stairs over processing equipment
  3. Specific areas of interest:
    • Seams and joints have permanent welds; are smooth; flush; resistant to stress
    • Seals and gaskets are removable or bonded; non-toxic; non-absorbent; non-extruding
    • CIP spray balls are designed to allow inspection and removal of debris
    • Conveyor belt is endless; no metal stitching or lacing


Specific criteria for evaluating dairy processing equipment

For specific dairy processing equipment, there are additional criteria in addition to the general criteria.

Butter equipment


Conventional churns:

Continuous churns:

Large continuous churns have product contact components of such size, weight and complexity that complete disassembly is a major undertaking. Therefore, cleaning reliance is placed on CIP procedures which are recommended by the churn manufacturer.

Buttermilk equipment

Buttermilk, the by-product of butter churning, may be sold for animal feed or receive further processing and be used for human consumption (for example, buttermilk powder, blending with fluid milk for use in other products).


Butter is wrapped in a continuous process using automatic printer-wrappers. There are various types of printers in use including pound, microprint and 25 kg. The butter is extruded through a die in the proper shape and cut off at the desired length.

Reworker (butter or cheese operations)

A reworker is used to prepare blocks of tempered butter for moulding and packaging in a print operation. Essentially it is an auger conveyor that makes the butter malleable as it travels to the print machine. It is important that the rework operation be carried out at the proper temperature to ensure good textural properties. Poor reworking that disrupts the butter emulsion will result in free water. These water droplets facilitate the activity of microorganisms and consequently the deterioration of butter.

Another example where reworkers are used would be during the processing of pasta filata type cheeses such as mozzarella cheese


When making butter from cream that needs neutralizing, the term "forewarmer" is used to designate a coil type vat for warming the cream for neutralization. The cream is then pumped out to the High Temperature Short Time (HTST) system or vats for batch pasteurization. When cream is neutralized and pasteurized in the same vat, evaluate the forewarmer using the criteria in Batch pasteurization.

Cheese equipment

Cheese vats

Curd knives

Cutting the cheese into uniform size cubes is important for proper cooking, salting and composition control. The knives used in open vats may be mechanically or manually operated. These knives are subject to a substantial amount of repair work due to their construction; the wires can be quite fragile.

Drain tables

Typically the drain table is a long rectangle with a central drain trough, covered by perforated or slotted drain plates. Some drain tables have gasketed, liquid tight end doors. In use, the curd/whey mixture is run from the curd vat into the tank.

Curd screens and sifters

Curd screens and curd sifters are used to remove curd particles from the whey. Due to the small holes in the screens, they are usually difficult to clean and should be carefully examined.

Agitator carriages

Curd mill

Most curd mills for cheddar cheese are rotary type, but Mozzarella cheese requires a dicer type unit that uses a plunger to force the curd through sturdy knives.

Wash water tank and filter

Following the cooking process, the cheese curd is washed.

Hoop filler

The hoop filler is used to direct cheese curd into cheese hoops.

Cheese hoops and moulds

Hoop and rack washer

Cleaning hoops and racks can be accomplished in a variety of ways, ranging from soaking them in cleaning solutions to automatic washing equipment. This activity produces high moisture conditions which are optimal for microbial growth.

If high pressure washing systems are used, aerosols are likely to form and pose microbiological risks. It is recommended that these systems be located outside of processing areas. If it is not possible to locate these pressure washer systems outside of processing areas, they can still be used to wash hoops and racks provided precautions are taken to ensure control of aerosols and other airborne contaminants.


The press compresses the cheese after it has been placed in the hoops. This aids the expulsion of whey and the development of a compacted cheese. Because the pressing step may be done under a vacuum it also assists in cooling the curd.

Press cloths

Press cloths are used in the pressing operation to aid in the development of a smooth rind. Traditional materials have been replaced with textured synthetic cloths; as well, finely perforated stainless steel moulds have eliminated the need for cloths.

Moisture probes

Moisture probes are used when making cheese in large styles, such as barrels, 640 pound blocks, etc. It uses vacuum probe equipment to withdraw whey from the cheese.

Chill tank

Moulded cheese is to be cooled before it is placed in the brine tank. Since chilling is a post pasteurization step, it is important that the water used be potable and the tank be in good condition.

Moulding equipment

The Pasta Filata category of cheeses includes such varieties as Mozzarella and Provolone. The curd produced in the manufacture of these cheeses is allowed to develop into a curd mass. This curd mass (plastic curds) is then kneaded and formed mechanically into moulds or shaped by hand. Although the curds can be manipulated by hand, the kneading process is generally done by machine.

Vacuum chamber

The pressing time of cheese blocks can be reduced by using vacuum to remove air from the curd and give a more compact cheese. It is important that this process does not contaminate the cheese. In particular, the contamination of the outer surface of the cheese with anything that is liable to modify the development of the surface flora (inhibitors or activators) should be prevented.

Brine tanks

Brine tanks can be constructed from a variety of materials which include concrete, glazed ceramic, fibreglass (acceptable food contact surface) and plastic. When choosing a brine tank it is important to consider the corrosive effect of salt and its impact on the external surfaces of the tank.

Draining racks

Draining racks are used in the manufacture of specialty cheeses. These racks are considered product contact surfaces.

Cutting equipment

Cutting equipment is used to cut blocks of cheese prior to packaging or for trimming before processing into process cheese.

Waxing tank

Varieties of cheese, such as Gouda, Danbo and Elbo may be coated with wax or plastic resins. Some cheese may be waxed over a bandage. The bandage should be dry so that the wax coat does not peel away. Waxes of different melting points are available. They range from 49°C to 82°C. The wax is to be applied at the correct temperature. If the wax is applied at too high a temperature there is a chance that steam pockets may develop and the wax will not adhere to the cheese. These steam pockets may also negate the mould growth inhibition provided by waxing. If the wax is applied at too low temperatures, the wax will also not adhere to cheese.

Cheese smokehouse

Smokehouses are used to impart a wood smoke flavour in the manufacture of cheese. They may be equipped with an indicating thermometer and recording chart.

Dry products equipment

Surge tank

Surge tanks may be located between the evaporator and dryer or a holding tank prior to a fluid milk filling machine. Because the product in the surge tank is pasteurized it is important that re-contamination of the product does not occur.

Whey crystallizing tank

Sweet whey contains approximately 5% lactose. In the range of 7-10°C this lactose will crystallize out of the whey. This crystallization process is done prior to drying to reduce the level of hygroscopicity. This minimizes the caking and lumping in the final powder. For successful crystallization agitation and temperature need to be well controlled.

High pressure pump

The high pressure pump is used to push the concentrated milk at high pressure into the spray dryer.

Drying chamber

The drying chamber may be used for drying milks and by-products or cheese to make cheese powder.

Cleaning procedures varies depending on the construction of the equipment. Many drying chambers are of the cone or tube type, and they are cleaned daily by dry methods. The frequency of wet cleaning is determined by the condition of the dryer chamber. Clean thoroughly to prevent the build-up of caked powder.

Although the main drying chamber of some dryers is routinely wet cleaned, the collectors, coolers and conveying systems are wet cleaned less frequently. It is important to prevent vapours from penetrating into these dry areas during wet cleaning of the main chamber. This can be achieved with valves, shut off plates on ducts, or making a complete disconnect by using polyethylene liners over openings etc.


Collector equipment includes bag type filters, cyclone type collectors, and wet scrubbers.

Collectors are used in the drying systems to separate the powder from the air. There are basically two dry types: bag filters or various modifications of the centrifugal cyclone principle. Bag filters are usually employed as a secondary collector (after the cyclone collector). Inspection is usually done by opening the drying systems inspection port or manhole and the condition of the bags is checked from the outside. It is not necessary to have bags removed for additional inspection. When the dryer is wet cleaned or when it is idle, it is imperative that the bag filters are protected against moisture pick-up.

Inspection ports or manholes on cyclone type collectors should be opened for inspection of interior surfaces. Some cyclone collectors are CIP cleaned. In this case check for proper cleaning of the interior surfaces.

In wet collectors or scrubbers, liquid milk or water scrubs the air from the cyclones by bubbling it through the liquid. The fines are removed from the air and the air is cooled prior to being exhausted. The scrubbing liquid is recirculated and periodically removed. The liquid containing the fines may be redried or disposed of. The conditions in a wet collector are ideal for microbial growth; thermophilic bacteria are a serious problem in the foam. Incorporation of these collected fines into the product going for drying is an acceptable practice if the fines are properly collected and handled.


Redryers are used to further dry partially dried product and for instantizing systems. In these redryers heated air is used so it is important to evaluate the quality of air going into this dryer.

Powder cooling system

Cooling of dry powder in most systems is accomplished by introducing the hot product into a stream of moving cold air. The mixture is then separated in cyclones and powder is discharged through an air lock device.

The air quality, the cooling equipment and moisture condensation does not pose contamination risk to the dried powders.

Since the cooling system handles only dried product, the related piping, cyclone, and fan usually do not require frequent cleaning. When the rest of the dryer system is wet washed, there should be segregation of the cooling components to protect them from water splashing and humid air.

In order to improve the efficiency of a powder cooling system, sometimes provision is made for water or mechanical refrigeration cooling of the air before the powder pickup point. Air drawn for cooling should be properly filtered. Most of these cooling units are of fin and coil construction and are difficult to clean. The presence of accumulated powder in these units results in unpleasant odours and poor sanitation conditions.

Some dry powders are cooled with jacketed equipment. Ensure that this is properly constructed and operated to prevent moisture condensation on product contact surfaces.

Storage bins

Frequent cleaning is usually not necessary if the storage bin is kept closed and in dry condition. Wet cleaning frequency will depend on actual need conditions.

A storage bin is usually equipped with a top vent to allow air escape and entrance during filling and emptying operations. Such vent openings are equipped with a suitable filter. This filter will prevent escape of product dust and filter air entering the bin. Usually the filters are sock type or cartridge units.

Exhaust stack

Exhaust stacks are part of the spray drying systems from where dryer or cyclone air is exhausted to the atmosphere. Some dryers have two or more exhaust stacks. It is important that exhaust stacks have self-closing doors to prevent environmental contamination from entering the drying system.

Cooling tower

Non-potable water is sometimes used in evaporators with open or closed condensers. Such water might be recirculated on cooling towers to cool it. Cooling towers are usually located on the roof and are often the cause of roof deterioration.

Vacuum cleaner

Dry cleaning is applicable in situations in which the soil is dry and relatively fine and where wetting this soil could hydrate it to the point where microbial growth could occur. Dry milk powder establishments use dry cleaning techniques in the drying and packaging areas. Brooms and hand sweepers which can be used for this purpose usually create dust problems and redistribution of the dust material. Vacuum cleaners are the best alternative for this purpose.

Vibrating sifter and screen

Milk powder is sifted to produce a finished product of the desired granule size. Like other parts of equipment within the drying process, routine dry cleaning (vacuuming) is performed, with wet cleaning when needed. The effectiveness of dry cleaning may be reduced when drying hygroscopic products such as lactose or protein powders.

Stainless steel mesh is most commonly used for screening surfaces; others used include cotton, linen, silk or synthetic fibres.


Hoppers need to be monitored to ensure they do not retain product for excessive periods of time, creating a risk of microbiological contamination.


Agglomeration is the process of sticking smaller particles together to make larger particles so that a dried product is easier to reconstitute. This is also referred to as "instantizing".

Sizing rolls

This equipment is used in the instantization process and is usually located after the redryer.

Shaker table

The Shaker table is used after the redryers in the drying process to remove the "tailings" from the dried product.

Evaporated products equipment


Hotwells are tanks located upstream of the evaporator used for product preheating. Preheating reduces the microbial flora, increases the effectiveness of the evaporation process and stabilizes the proteins.


Evaporators may be of different types: for example rising or falling film, or plate type. Evaporators usually have multiple effects; newly designed evaporators have multiple tubular passes instead of multiple effects.

Fluid milk products equipment

Case washing room

This area potentially poses a microbiological contamination risk because of the high humidity conditions.

Ensure that returned cases are gathered in an area that is physically separated from the processing area to reduce the risk of contamination of the processing environment.

Case condition and handling

Plastic cases are used in the transporting of fluid milk and other dairy products.

Frozen products equipment

Liquid sugar tank

Flavour tanks


The freezer includes the barrels (there may be numerous ones in one freezer), blades, pressure dials, air intake freezer pump, and pipes.

Mixing vat

This applies to vats used for mixing previously pasteurized or microbiologically safe components with subsequent hygienic handling.

Fruit feeders

Fruit feeders inject fruit and nuts into the finished ice cream as it is discharged from the freezing chamber and may also be used to add fruit to vat set style yogurts as they are packaged or into the yogurt cup during the filling operation.

Ripple pump and equipment

This includes the ripple tank, positive pump, ripple tube and ripple head.

Novelty equipment

Novelty machines form, freeze and package items as a complete process. Due to their design, these machines are inherently difficult to clean properly. Most product contact surfaces (moulds, extrusion nozzles) are designed to be cleaned out of place. Keeping the non product contact surfaces, such as the housing and drive units, clean can be much more difficult. For example, product may seep into the drive unit and the undercarriage as a result of the equipment jamming.

Generally, rotary and line types of equipment are used to make the stick novelties. The moulds of stick novelties are submerged in a refrigerant (brine or glycol) and the product is added in a liquid or semi-liquid state. The sticks are inserted, the product is extracted and coatings, nuts, etc. may then be applied before packaging. Other machine types may have enclosed cooling medium systems.

Extrusion equipment includes a product extruder, cookie dispenser, nut dispenser, enrober (adds coating), wrapper and in some cases a stick inserter. For this type of novelty, cold-air hardening is employed.

Process cheese equipment

Grinders / graters

Grinders/graters are used to convert cheeses into small pieces or filaments or even to a fine powder. This ground product may be used as an ingredient in other foods, made into a processed cheese product or sold as a grated cheese. Grating the cheese also facilitates the heating process.

The grating process increases the exposed surface area of product and thus increases the likelihood of bacterial contamination. Proper maintenance is required to ensure that foreign matter is not incorporated in the grated cheese mass. Ensure that metal detecting devices are incorporated with this equipment.

Weigh tank

This includes the containers or weigh scales used for weighing, measuring or metering liquid products used as ingredients.

Premix equipment

Premix equipment may be used for the incorporation of herbs, nuts and other flavourings with cheese curd prior to moulding and pressing. As well, in process cheese manufacture they are used for the blending of batches of cheese prior to cooking. As ingredients are being added to the vat, it is imperative that extraneous matter is not allowed to get into the tank.


An extruder is a piece of equipment used to shape products.

Vacuum treatment equipment

The vacreation process is used to remove volatile substances that are responsible for unpleasant flavours and odours in milk based products. It is a steam distillation process where pressurized steam is mixed with, for example cream, and the condensed vapour plus volatiles are removed by flash evaporation under partial vacuum.

Raw receiving equipment

Milk metering system

This includes all major components of the system and includes the deaerator, air eliminator, the meter itself and the filters. Since these systems may be used for payment or claim purpose it is important that the system is mechanically in good condition. Type A or E (depending upon provincial requirements) systems are used for this purpose. The accuracy of the meter is directly related to the physical condition of the impeller (ebonite) and the gasket.

Mechanical sampler

Samples for microbial and composition analysis are taken as the raw milk enters the plant. Sampling devices tend to be made up of small parts and thus may become plugged with milk.


Stainless steel cans and plastic (20 L) pails are sometimes used within the establishment to move products and prepare starter culture.

Can washer and steamer

In mechanical can washing, the can is usually passed over a succession of jets emitting water, cleaner solution, hot water, steam and air. Temperatures usually used for wash solutions range from 55 - 60oC and for final rinses are 88oC or higher.

Universal equipment

Indicating thermometer

This covers thermometers used to monitor temperatures in hotwells, etc. For indicating thermometers used in critical processes, refer to the criteria in High temperature short time (HTST), Batch pasteurization, Aseptic processing and packaging systems, Non-thermal processing (starter vats section) and Retorting (canning).

Recording thermometer

This is the instrument which automatically records the temperature of the product on a chart thereby providing a record of the process.

Storage tanks

Storage tanks are used to hold cooled milk that is received at the plant, as well as process milk-based products such as ice cream mix. These tanks may be either horizontal or vertical. The latter, generally large silos, are located at the exterior of the establishment.

The walls of the tanks are insulated. Ideally, the temperature of the product should not increase more than 2°C (4°F) in a 24-hour period. If the product is to be held more than one day, refrigeration on tank walls may be required.

Agitation in storage tanks prevents fat separation and in the case of refrigerated tanks, aids in temperature control. Agitation may be mechanical or by air. Air may be used for agitation.


Pump design is a critical feature with respect to ease of cleaning. Proper cleaning will aid in the prevention of contamination of milk based products that come in contact with the pump.

Pipelines and valves

If they are not kept clean, pipelines and valves pose a contamination risk at product contact surfaces. This includes the interior of the pipes, the junctions between pipes, and certain parts of the valve.


The separator/clarifier is a piece of auxiliary equipment that mechanically separates milk into fat and skim milk by centrifugation. Self-cleaning separators also provide a clarifying function by regularly desludging the somatic cells, leucocytes and other inedible materials.

Refer to High temperature short time (HTST) pasteurization for more information on the use of separator/clarifiers in these types of systems.


Packaging and sealing equipment

Packaging protects the product from contamination and ensures the integrity of quality factors such as flavour and moisture content. There are two potential risks:

  1. Contamination that can be carried into or onto the food itself by the packaging and sealing process.
  2. Contamination that might occur if the package or seal barrier is broken or compromised in some way.

Packaging and/or sealing may be done by the equipment alone or by means of vacuum, heat, hot water or gas flushing.


Automated fillers are used to full containers with milk or milk products (soft cheeses, ice cream, process cheese, and yogurt).


Blenders are used to blend dry ingredients such as milk powders and other dry ingredients to the fluid milk portion of milk-based products (for example starter culture fermentation base). This evaluation covers industrial blenders, blender horn assemblies and tanks used to blend or mix dry ingredients. It also covers similar equipment used to melt and/or texturize the product (for example for processed cheese processing).

Conveying equipment

Conveying equipment is used to move product from one area of the operation to another. Examples of conveyor types include augers, belts, rollers, chains, bucket elevators, pneumatic systems and carts.

The risk of product contamination is dependent on the degree of direct contact with the product and the type of conveying equipment.

Salting equipment

This equipment is used to add salt to butter and cheese (including processed cheese).

There are various salt addition techniques, ranging from simple manual methods to automated equipment.

Supplementary utensils

This covers all the various small tools and equipment used in the establishment.

Packaging tables

Packing tables are contamination risk because they are a direct product contact surface.


This refers to the filtration of dairy products such as cream, evaporated milk, and hot processed cheese.

These filters are used to remove foreign particles (for example gaskets, brush particles, etc.). Cream filters are required when cream is transported from establishment to establishment or if the cream is vat pasteurized. If a closed HTST system is used it is desirable but not necessary to filter the cream prior to churning.


This refers to scales used in the processing area as well as those used for bulk and retail sales. It does not include analytical balances in the laboratory.

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