• Food processing equipment is an umbrella term referring to

the components, processing machines, and systems used to

handle, prepare, cook, store, and package food and food
products.
• Although this equipment is primarily aimed toward the
transformation—i.e., increasing the palatability,
consumability, and digestibility—or preservation—i.e.,
extending the shelf life—of food, some pieces of equipment
are also employed to perform preliminary or auxiliary
functions, such as handling, preparation, and packaging.
• Sizing
• There are several factors which help determine the optimal
size for food processing equipment, but ultimately, the goal is
to balance the material and resources used for each unit
operation and the required production output.
• Typically, processing equipment is oversized between 10–20%
to compensate for potential operational issues, such as
equipment breakdown or demand fluctuation, or
environmental conditions, such as temperature or humidity
changes.
• However, depending on the production requirements of the
particular facility, multiple, small-sized equipment can also be
employed to allow for greater operational flexibility.
• Cost
• While it is necessary to choose equipment which effectively
fulfills the requirements of the food processing application, it is
also important to consider the overall costs to better determine
whether the particular selection is worth the investment. Some
factors to consider when doing a cost-benefit analysis include:
• Construction Material: The majority of the cost of processing
equipment can be attributed to the construction materials as
the raw materials typically used (e.g., carbon steel, stainless
steel, aluminum, etc.) can range between a couple hundred to
a couple thousand USD per ton. The materials chosen can also
influence the cost of the actual construction process, as
different materials may have different handling and fabricating
requirements such as treatment procedures or higher precision
machining.
• Standard vs. Custom Equipment: As expected, custom-
designed equipment is more expensive than standard, off-the-
shelf equipment. Therefore, if possible and suitable, industry
professionals and procurement agents should opt for the
latter type, especially for processing products such as pumps,
heat exchangers, valves, evaporators, distillation columns, and
centrifuges.
 Materials of construction
• Materials of construction are usually selected based on their strength,
elasticity, hardness, toughness, sensitivity to wear, corrosion and
fatigue resistance, ease of fabrication, availability and cost price.
• However, in the construction of food processing equipment and
services, the hygienic properties of materials of construction, such as
sensitivity to fouling, cleanability and inertness in contact with the
food produced, are as important.
• To select the most appropriate materials of construction for use in
either the food contact, either the non-food contact area, the
equipment manufacturer must have knowledge of the physical,
chemical and thermal behaviour of an as large as possible range of
market available materials of construction, must be familiar with their
hygiene characteristics, and must have insight in the laws, regulations,
standards and guidelines applicable to the materials of construction
used in the design and manufacturing of food processing equipment
 General recommendations
• Materials of construction for food processing equipment,
process piping and utilities should be :
• homogeneous, hygienic (smooth, nonporous, non-absorbent,
nontoxic, easy cleanable, impervious and non-mould
supporting),
• inert (non-reactive to oil, fat, salt, etc.; may not adulterate
the food by imparting deleterious substances to it, nor affect
its organoleptic characteristics),
• chemical resistant (corrosion proof; non-degrading and
maintaining its original surface finish after sustained contact
with product, process chemicals, cleaning agents and
disinfectants)
• physically durable and mechanical stable (resistant to steam,
moisture, cold, heat; resistant to impact, stress and fatigue;
resistant to wear, abrasion, erosion and chipping; not prone to
cracks, crevices, scratches and pits; unbreakable) and easily to
maintain
• Copper
 The best known applications of copper are vessels, traditionally used in
many breweries and distilleries.
 Copper is largely applied in the non-product contact area, with as main
application the tubes in evaporators installed in refrigerators and
freezers, electrical wiring, water pipes, etc.
 According to recent research, copper has shown to restrict bacterial
growth.
 Copper does not really constitute a food safety problem but it is
recommended to avoid direct food contact with copper utensils, as it
can cause unacceptable organoleptic effects.
 Moreover, copper can be quickly and severely affected by strong
alkaline detergents, sodium hypochlorite, acid and salty food, making it
not really suitable in the food contact zone.
 The rate of attack is slow enough that alkaline detergents can be used
for the cleaning of copper vessels. As copper ions may leach from the
copper metal, its surface roughness may increase. Oxidation of copper
gives rise to the formation of toxic copper (II) oxide
• Aluminium
 For food contact purposes, anodized aluminium should be used because
uncoated aluminium is attacked by acid food and alkaline detergents.
 The use of silicates, however, prevents alkaline attack of aluminium. The
use of uncoated aluminium utensils should be limited, even if the
exposure to aluminium is usually not harmful.
 When coated, this coating must be resistant to alkaline detergents,
chlorine containing bleach, and acid and salty food.
 Anodizing is an electrolytic passivation process used to increase the
thickness of the natural oxide layer on the surface of the aluminium.
 Aluminium anodized coatings are resistant to many inorganic chemicals in
a range between pH 4 and 8.5 but are subjected to pitting in aerated
chloride solutions.
 An optimum resistance to corrosion is obtained if the coating is in the
thickness range of 18-30 µm.
 The corrosion resistance of anodized coatings can be further enhanced by
sealing the pores of the coating and incorporating inhibitors. However,
dichromate coatings containing hexavalent Cr(VI) shall not be used for
that purpose as it is toxic
• Mild steel
• Mild steel (also called carbon steel) is made from iron and
carbon (< 1%) without addition of other “alloying elements”.
Carbon steel will quickly corrode on exposure to moisture and
atmospheric air.
• It is also sensitive to acids, salt water and chlorine containing
bleach, but fairly good resistant to neutral and alkaline liquids
(high pH).
• Due to its corrosion sensitivity it cannot be used in the food
contact area, but it is often used in the construction of valves
for non-food applications
• Stainless steels
 The main elements in all stainless steels are iron, chromium,
molybdenum and nickel, with none of them being harmful to consumer
health.
 Especially the austenitic chrome-nickel or chrome-nickel-molybdenum
steels are used for the construction of equipment and services in the
food industry.
 Stainless steel AISI SS 304(L) can be used for the construction of food
processing equipment and service systems in applications with low
chloride levels (up to 50 mg/L [ppm]), near neutral pH (between 6.5
and 8) and low temperatures (up to 25 0 C).
 Due to its sensitivity to sodium hypochlorite and salt that is usually
present in food in high contents, the use of stainless steel AISI SS 304(L)
should be limited to exterior equipment surfaces, motor and electrical
cabinets, etc.
 Susceptibility to chloride attack is especially high if the water has an
acidic pH, and can be further accelerated in the presence of oxidizing
agents.
 The small additional cost of using AISI SS 316(L) rather than AISI SS
304(L) makes that stainless steel AISI SS 316(L) is commonly used
as construction material for food processing equipment.
 If the stainless steel is provided with a coating, that coating must
be inert, chemical resistant, physically durable and easy to clean.
 However, as temperatures approach 150 C, even AISI SS 316
stainless steels may suffer from stress-corrosion cracking in
regions of high stress and exposed to high levels of chloride.
 Therefore, other stainless steel types were developed to
overcome that problem (e.g., duplex steel).
 Duplex stainless steel has higher strength and toughness, higher
corrosion resistance (it remains intact in contact with aggressive
foodstuffs and saline solutions at high temperatures), and
excellent resistance to stress corrosion cracking and corrosion
fatigue.
 Other stainless steel types are the super-austenitic grades, which
are used in similar applications and also for steam heating systems
 Plastics–Rubber Plastics
• Plastics–Rubber Plastics are usually resistant to corrosion, but
their mechanical strength is limited.
• Furthermore, their strength depends strongly on the
temperature of the material. The upper temperature application
limit of most temperature-resistant plastics lies at 250 C.
• Therefore, in food processing equipment, plastics are mainly
used for coating and parts that are not under high and
continuous stress (e.g., parts of ventilators and pumps, pipes,
fittings, small tanks, covers of vessels, filters, gaskets).
• In all cases, plastics must fulfill the requirements concerning the
interaction of materials with food. This is especially important
for plasticizers, which are added to influence the properties of
the plastics and which are generally undesirable in the food
system.
• Plastics, as construction materials, can be divided into two main
categories: thermoplastic and thermosetting materials.
• Examples of commonly used thermoplastics are poly(vinyl
chloride) (PVC), polyethylene, and poly (tetrafluoroethylene)
(PTFE; Teflon).
• Depending on the plasticizers added, plastics could become
softer or harder. Polyethylene, for example, can be distinguished
into low- and high-density material.
• The tensile strength of low-density polyethylene is 15 MPa,
while that of the high-density material is about double. Low-
density polyethylene can be used at temperatures up to 100 C,
while the high-density material can be applied at temperatures
up to 130 C.
• The thermal conductivity of both materials is 0.334 W/m K.
PTFE has relatively low mechanical strength but it is used when
high temperatures prevail, as it withstands temperatures up to
250 C
• Examples of thermosetting materials are polyester and the
epoxy resins.
• The tensile strength for polyester is 40–100 MPa and, for epoxy
resins, it may reach 200 MPa.
• The thermal conductivity of polyester is 0.13–0.26 W/m K.
• Epoxy resins are also used as adhesive of plastic or even metal
equipment parts.
• However, in this case, the application temperature should not
exceed 100–180 C .
• Rubber is used as part of equipment or machines coming
directly in contact with food (e.g., gaskets, filters), as parts that
must withstand friction (e.g., pumps), and in coating of metals.
Rubber must be as pure as possible.
• Hard rubber has a tensile strength of 70–100 MPa and its
thermal conductivity is about 0.4 W/m K.
• In conveyor belts, canvas may be more preferable than rubber.
• Glass
 Glass is transparent, and may occasionally be used as a food
contact surface (e.g., light and sight glasses into vessels, and
in very limited extent glass piping).
 For such applications, glass should be nontoxic (glasses
containing lead are not allowed in the food contact area),
integral (homogeneous and continuous), impervious, inert
(nonabsorbent, resistant to degradation, and insoluble by
process or cleaning fluids), smooth (free of cracks, crevices
and pits), durable (robust, heat resistant, resistant to
scratching, scoring and distortion when exposed to
bioprocessing fluids).
 Glass shall be rated for the applicable pressure and
temperature range, as well as for thermal shock.
 Bubbles at the glass surface are not accepted.
 However, that the surface of glass is not completely smooth. It
rather has a rough surface made of peaks and pit holes that
can be filled with organic and inorganic contaminants.
 When these impurities react chemically with the glass, the
glass easily may become stained and discoloured.
 Glass also may become prone to hydrolytic and chemical
attack by certain alkali and acid solutions, which even can
make the glass surface much rougher.
 Resistance to water and/or acid/alkaline solutions varies from
excellent to poor depending on the composition of the glass.
 It is important to choose the right type of glass. In most cases,
the use of glass is not recommended because it is also brittle,
may break and cannot endure thermal cycling. Replacement
of glass by transparent alternatives like Perspex (poly methyl
methacrylate) or polycarbonate is recommended
• Ceramics
 Ceramics are produced by the fusion and hardening of mineral
substances.
 Fired at high temperatures, they become pressure, temperature,
abrasion, high-temperature corrosion and erosion-corrosion
resistant.
 They may reduce friction and wear; but are brittle (they rather
break than bend) and weaker in tension. However, by adding small
amounts of long organic polymers, less brittle and less prone to
fracture, more flexible organo-ceramics can be obtained.
 In general, ceramic materials are also very resistant to acids and
sufficiently resistant against lye.
 Ceramics are more and more employed in the food industries due
to their resistance to extreme operating and cleaning conditions.
They are used in the coating of other stable materials, in the
production of ceramic membranes and in the construction of
processing equipment for very sensitive products
• Wood
 As it is inexpensive and durable, wood (hard marple, ash,
basswood, beech, birch, butternut, cherry, oak and American
black walnut) has been a traditional material for many
applications in the food industry: ice cream sticks, cutting boards,
vegetable and fruit boxes, pallets, etc.
 Today, the usage of wood in the food industry remains under
debate.
 Wood is out of grace because of hygienic and mechanical strength
problems: risk of splinters, porosity of wood (promotes the
absorption of blood, fat and moisture), difficulties to keep it
smooth and free of cracks, difficulties to keep it clean and
hygienic due to the lack of cleaning and/or sanitation methods,
etc.
 Moreover, strong and oxidizing acids and diluted alkalis may
attack wood.
 To avoid pest infestations and the growth of moulds with
concomitant production of mycotoxins, wood in contact with
food is also often treated with pesticides and fungicides.
 Control for the presence of residual levels of these fungicides
and pesticides in the food in contact with the wood should be
performed
 The use of wood is not really recommended.
 On some exceptions, wood is certainly not allowed within the
product contact area, and should not be exposed to the
outside.
 It must be permanently and tightly sealed off from the
product zone.
 Fabrication of Equipment
• The requirements for construction of food processing
equipment are to a great extent similar to those applied in
building general processing equipment.
• However, due to the biological character of the processed food
materials, certain limitations, influencing their quality and safety
(e.g., temperature, moisture, pressure, contact with air), must
be taken into consideration.
• The designer of food equipment must keep in mind the selection
requirements of the final user in the food industry who will play
a role in purchasing the constructed equipment, and a feedback
of experience.
• The following basic points must be taken into consideration for
the proper design and construction of food equipment :
strength, technological suitability, weak construction points, and
fabrication and installation of equipment.
 General Aspects
• The basic types of forces applied in a material are tension, pressure,
and shear. Furthermore, combinations of these forces, such as
bending or perforation, are often applied.
• The stress applied to machine materials is due to forces caused by
mechanical, thermal, chemical, or physical processes (e.g., phase
change of a processed material).
• Food equipment stresses may be distinguished as “internal” and
“external” stresses. Mechanical stresses may be due to static forces,
as in silos or tanks (weight of the equipment and weight of its
contents).
• Other examples of mechanical stresses are the pressure
experienced by materials of construction during mechanical
processing, such as homogenization, pressing, filtration, extruding,
and pumping.
• Thermal stresses develop at high or low temperatures during
processing (expansion/contraction).
• They are especially pronounced in positions in which two different
construction materials are joined. Furthermore, elevated
temperatures may cause mechanical weakening of the material.
• Chemical reactions influence directly or indirectly the strength of
the construction material.
• Chemical reactions may cause corrosion or produce substances that
cause mechanical stress (e.g., gases).
• Physical stress may cause indirectly mechanical stress. Phase
changes of the product may cause mechanical stress, such as when
water is vaporized (development of pressure).
• Internal stresses are related directly to the equipment, including
static forces of the equipment and its contents, and forces caused
by changes during food processing. External stresses are usually
caused by external forces such as wind and snow.
• These stresses occur when the equipment is located outside
buildings e.g., in silos, large tanks, and tall equipment, like
barometric sterilizers, large evaporators, and distillation columns.
• However, external stresses may also be important in
equipment located indoors, e.g., stresses due to seismic
action or due to vibration of neighboring equipment.
• Mechanical stresses can be controlled and minimized by
proper selection of the construction materials, correct design
of the equipment, and proper construction.
• Recommended design stresses must be taken into
consideration; e.g., the tensile strength of stainless steel 304
at 20–50C is greater than 500 N/mm2 , but typical design
stress for such a material is only 155 N/mm.
• Thermal stresses in pipelines should be controlled by flexible
connections or Ω expansions.
• Proper construction should apply sufficient tolerances against
the risk of thermal expansions and contractions.
• Proper welding may reduce the risks of equipment corrosion or
stresses, since welding is the weak point of several structures, due
to the weakening effect of the local heat, produced during welding.
• Besides that, the electrolytic corrosion should be avoided by taking
special constructive measures.
• In case, for example, of using steel bucket supports, in stainless
steel equipment or tanks requiring free space beneath, welding
should be done.
• In storage silos (bins), material failure of the lower cone may be
caused by uneven distribution and improper emptying of the
particulate material.
• Silo failure is a potential explosion hazard for certain food powders.
• To prevent this problem, emptying of the particulate material
should be facilitated by special devices and techniques. Metal
support rings should be installed near the wider base of the metal
cone, reinforcing the walls against excessive stresses
 Sensitive Construction Points
• Sensitive and weak points in food processing equipment include
• (1) material joints and
• (2) parts for which a relative motion between equipment
elements exists. Joints may be permanent (welded, riveted plates,
parts connected with an adhesive) or flexible (screwed parts).
• Adhesives are frequently used in constructions, e.g., in
pipelines ,but they do not withstand high temperatures, and the
additives (plasticizers) they contain are not acceptable for direct
food contact.
• Welding, which is used extensively in joining various metal parts,
should be polished in all surfaces coming into contact with food
materials.
• Screws should be avoided in equipment parts contacting food.
• Screwed joints, used in external construction (supporting
structures), should conform to sanitary requirements, e.g.,
wide-pitched screws and very short (hidden) nuts .
• For the same reason, wide-pitched (thicker) coiled springs
should be also preferred instead of thinner ones.
• Bearings should be placed outside the food area, when a part
of the equipment is stationary, while the other is rotating,
e.g., shafts connecting an electric motor with agitators,
extruder screws, scraped heat exchangers, or pumps.
• Food-grade gaskets should be used instead of full face ones,
to avoid contamination
 Proper Engineering
• In relating a given food processing technology to the
construction of proper equipment, in addition to the sizing and
economic factors, the interrelation of equipment with its
environment (surroundings) must be taken into account.
• The interrelation of equipment and its surroundings may or may
not be desirable.
• For example, in heat exchangers, the transfer of heat between
the product and the surrounding medium is desirable.
• On the other hand, undesirable interrelations include the
leakage of equipment [loss of material (processed food), loss of
heating medium (hot water or steam), inflow of air in vacuum]
and contamination (inflow of microorganisms or undesirable
fluids in food processing pipes).
Fabrication and Installation of Equipment
• The principles and techniques used in the fabrication of
process equipment for the chemical and other process
industries are applicable to the food processing equipment.
• In addition, the food equipment must comply with strict
hygienic (sanitary) standards and regulations, which will
ensure the safety and quality of the food products.
 General Process Equipment
• Fabrication expenses account for a large part of the purchased
cost of the process equipment.
• Mechanical details for the fabrication of general process
equipment are given in various engineering codes, such as the
American Society of Mechanical Engineers (ASME), the British
Standards (BS), and the German Institute for Standardization
(DIN).
• The main steps in fabricating process equipment are cutting,
forming, welding, annealing, and finishing
• Cutting of the metal can be affected by shearing, burning, or
sawing.
• Forming into the desired shape is accomplished by rolling,
bending, pressing, pounding, or spinning on a die.
• Welding has replaced bolting in most metal constructions.
• Electric welding can be done by manual shielded arc or
submerged arc.
• Stainless steel and nonferrous metals are welded by the Heliarc
process (in inert He or Ar gas).
• The welded joints and main seams are tested by X-rays.
Hydrostatic tests are required to detect any leaks.
• Heat treatment (annealing) of the fabricated equipment is
necessary to remove mechanical stresses, created during forming
and welding, to restore corrosion resistance, and to prevent stress
corrosion. The equipment is finished by sandblasting (abrasive) or
mechanical polishing, and it may be painted. Final pressure tests
at 1.5–2 times the operating pressure and other tests may be
required by the codes or the inspector.
• Metal cladding is sometimes used to reduce cost in corrosive
environments: a thin sheet of an expensive corrosion-resistant
material is used to clad (cover) a cheaper thick plate. In the design
of process vessels (tanks), empirical correlations are used to
ensure the mechanical strength of the construction. Thus, the
ratio of wall thickness to tank diameter (t/D) is taken as t/D <
1/10 for thin-walled vessels and t/D > 1/10 for thick-walled
vessels.
• Empirical correlations are also used for liquid storage tanks
 Food Processing Equipment
• The fabrication of food processing equipment must follow some
special requirements, related to the materials of construction,
the design, and the characteristics of the various units.
• The materials used in food equipment and machines should not
interact with food and should be noncorrosive and mechanically
stable. For the majority of equipment used in direct contact with
food, stainless steel (AISI 304) is employed. If the acidity of food
products is high, AISI 316 is commonly employed.
• If rubber and plastics are used in contact with foods, e.g., PVC,
plasticizers that may migrate into the food should be contained.
Tin, although nontoxic for normal dietary ingestion, should not
be used in food equipment and machines if mechanical stresses
occur, since its strength against stress is very low
• The cost of equipment/machines increases with
• (1) quality and quantity of stainless steel used, (2) total weight of
the unit, (3) quantity of relatively expensive material used (e.g.,
insulation, special seals), (4) fabrication (e.g., smoothness of
surfaces, type of welding), (5) antirust protection (e.g., double or
electrolytic galvanization, special paints), and (6) quality of spare
parts (e.g., bearings, electrical material).
• In addition to the hygienic design (e.g., cleaning, sanitation), the
following requirements are important in the construction of food
processing equipment: (1) easy mechanical maintenance; (2)
standardization of spare parts, important in seasonal processing,
when the equipment is run continuously for a relatively short
time; (3) durability and flexibility, important in seasonal
processing and in switching from one product to another; and (4)
high accuracy in some operations, like peeling, cutting, filling,
packaging, and weighing.
• The food contact surface of the equipment should be kept
free of nonfood materials, like lubricants and greases, using
gaskets, seals, and other insertions. Bearings and other
mechanical parts should be isolated from the food.
 Installation of Process Equipment
• The process equipment is installed on various supporting
structures, depending on the type and weight of the equipment
and the nature of the processing operation.
• Large and heavy equipment, e.g., barometric sterilizers and
homogenizers, are installed directly on heavy ground foundations.
• Large and tall equipment, requiring free space beneath it, like
silos and storage tanks, are normally seated on bucket supports,
welded on the surface of the equipment, near its center of gravity.
• Between the stainless steel apparatus wall and the steel
supporting its elements inserts a stainless steel plate welded on
the apparatus wall.
• This eliminates apparatus damage due to electrolytic corrosion.
Supporting legs are used for short vessels and long structures,
e.g., sorting tables and band dryers.
• Equipment that has to be transported frequently within the
plant from one area to another, e.g., silos containing
semifinished products, can be installed on moving supports,
hanging from the plant roof.
• Equipment supports, made of carbon steel, like legs and
bucket supports, should be welded to stainless steel patches,
which are in turn welded on the processing equipment.
• This construction of equipment prevents electrochemical
corrosion, caused by joining two dissimilar metals.
 Hygienic Design of Food Processing
• Equipment Hygienic or sanitary design of food processing
equipment is based on proper selection of construction
materials and fabrication techniques, which will facilitate food
processing and thorough cleaning of the equipment.
• Hygienic design of process equipment must be accompanied
by a thorough hygienic design of the whole food process and
processing plant .
• Engineering implications of hygienic process design should be
considered from the outset of the design process, especially for
new, untested food processing systems .
• The European Union (EU) research and development program
LINK includes a project on advanced and hygienic food
manufacturing, consisting of hygienic processing and food
process simulation and modeling.
 Hygienic Standards and Regulations
• The design and operation of food processes and processing
equipment should ensure the microbiological safety of the
final food products.
• Design engineers, equipment manufacturers, and food
processors should follow strict hygienic standards and
government regulations.
• Government regulations of food processing equipment are
essential for the manufacture of safe and wholesome foods
and the protection of public health.
• In addition to the hygienic design of food contacting surfaces,
process equipment should be designed to protect from external
contamination (e.g., covers for processing equipment, proper
drainage of the outside surfaces).
• A number of guidelines have been published by EHEDG, which are
voluntary and complementary to the corresponding national and
international hygienic standards. The EHEDG guidelines include the
following:
 Microbiologically safe continuous pasteurization of liquid foods
 A method for assessing the in-place cleanability of food processing
equipment
 Microbiologically safe aseptic packing of food products
 A method for the assessment of in-line pasteurization of food
processing equipment
 A method for the assessment of in-line steam sterilizability of food
processing equipment
 The microbiologically safe continuous flow thermal sterilization of
 The EC (European Community) Machinery Directive and food
processing equipment
 A method for the assessment of bacterial tightness of food
processing equipment
 Hygienic equipment design criteria
 Welding stainless steel to meet hygienic requirements
 Hygienic design of closed equipment for the processing of
liquid food
 The continuous and semicontinuous flow thermal treatment of
particulate foods
 Hygienic design of valves for food processing
The need for thorough hygienic design and operation of the entire
food processing line is very important in food processing: A weak
link in the processing line can nullify the whole hygienic operation.
 Cleaning of Food Equipment
• Cleaning and sanitation should be considered an integral part
of food process design and food processing operations.
• The food processing equipment should be designed to facilitate
the removal and draining of all of the process effluents (steam
condensate, waste solids, e.g., peels).
• All dead ends in tanks, containers, and piping should be
eliminated. Fouling is particularly important in heat exchangers
and other installations involving fluid flow (e.g., tubes, filters,
cyclones).
• Empirical models have been suggested to describe heat-
induced fouling and its relationship to the overall heat transfer
coefficient (U) and the pressure drop (ΔP)
• The food processing equipment must be cleaned easily either by
quick dismantling and cleaning of the parts or by cleaning-in-
place (CIP) techniques.
• The equipment of small food processing plants is usually
cleaned by periodic dismantling of the principal units, such as
pumps, plate heat exchangers, and filters.
• Quick dismantling and reassembling of process piping is
facilitated by various hand-opening clumps.
• The design and installation of CIP systems in large food
processing plants requires specialized experience in pipe flow,
sanitation, processing operations, and process control.
• The CIP system involves the following sequential operations: (1)
prerinsing with cold (soft) water, (2) alkali wash (supplemented
with sodium hypochlorite), (3) intermediate water rinse, (4) acid
rinse, (5) final water rinse, and (6) rinse with sanitizing solution
(sodium hypochlorite) or flushing with hot (90C) water.
• The CIP system is essentially a chemical cleaning operation, in
which the chemical solution is brought into intimate contact with
all soiled surfaces.
• Addition of surface-active substances, reducing substantially the
surface tension of water, facilitates the penetration of water and
aqueous cleaning solutions into crevices of the equipment.
• The required tanks, pumps, pipes, valves, and heaters (heat
exchangers or steam injection devices) are used as either single-
use or reuse (recirculation) systems.
• In large continuously operated units, double seat valves enable
the cleaning of a part of the processing equipment, while other
processing areas continue production.
• Air-operated piston or diaphragm-type pumps are used to feed
the chemical solutions. For safety reasons, the pumps and the
chemical supply containers are enclosed in a separate
compartment of the processing plant.
• Ball spray or rotating nozzles are commonly used to clean
process and storage tanks.
• Cylindrical and rectangular tanks are cleaned using liquid feed
rates of 8–12 L/min m2 internal surface, while vertical silos
require liquid rates of 25–35 L/min m tank circumference.
• The fluid pressure in cleaning varies according to the dimensions
of the tank/equipment, the surface it has to be cleaned, the
product it was processed or stored, and the kind of processing
before cleaning.
• Usually this is 3 *10^5 to 5 *10^5 P.
• Ball or other spray devices are common in CIP installations.
• The ball nozzles vary according to the type, number, and position
of their holes. In larger installations, the nozzles are usually fixed
ball spraying devices. In smaller tanks, portable spraying
installations are applied.
• In larger continuously operating installations, double seat
valves are used, which allow cleaning of a single part of the
plant while other areas continue processing.
• The fluid pressure leaving the nozzles depends on the
equipment that has to be cleaned .
• It is usually 3.5 *10^5 P.
• Adequate inclination (slope) of piping and process vessels is
essential for self-draining of process and cleaning liquids.
• Special CIP systems are applied to dry food processing
equipment, such as conveyors (belt, screw, pneumatic), dryers
(e.g., spray, rotary), and dry food processing lines (e.g.,
cereals)
• Usually, food equipment must be cleaned daily, after a processing period.
• However, when different products are processed in the same equipment,
cleaning also depends on the frequency of product changes.
• If CIP is applied, the required valves and automation must also be reliable.
Cleaning and rinsing of equipment is difficult for very viscous fluid or
semisolid foods, like cream, yogurt, and fruit pulps.
• A cleaning system, used in the oil and chemical industries (pigging), has
been suggested for cleaning such difficult food pipes. A plug (pig) of food-
grade flexible material containing a magnet is forced through the pipeline,
removing the viscous material, before flushing with water and applying the
CIP system.
• Effective CIP requires automation of the whole system. Microprocessor
controllers (PLC) are used in connection with on-line sensors for
temperature, level, flow rate, pressure, and valve position.
• The concentration of cleaning agents and organic effluents can be
measured with pH meters, redox potential meters, and optical density
meters.
• The degree of surface contamination can be determined by pressure drop
measurements in the pipeline.
Selection of Food Processing Equipment
• Selection of Equipment
The selection of food processing equipment is based on the
suitability for the intended application, the constructional and
operational characteristics of the equipment, and the purchase
and maintenance costs.
• Construction Characteristics
In selecting food processing equipment, the following
construction characteristics should be considered:
dimensions/weight, cleanability, maintenance, standardization of
spare parts, quality of materials, strength/durability, and
automation.
 Dimensions/Weight
In plant design, the space occupied by the processing equipment
and its weight must be taken into consideration. These factors are
especially important in multistory food plants, i.e., where equipment
is installed on several floors. The dimensions of the equipment are
also important in extension or replacement of existing food
processing lines.

 Cleaning Facility
Food equipment is usually cleaned daily after processing, but if the
equipment is used in processing different products (e.g., a mixer), it
must be cleaned before switching to a new processing program. In
this case, easy and quick dismantling and assembling is essential, and
joints and connections requiring minimum labor are necessary. If CIP
is used, the valves and automation of the system should be reliable
and resistant to the cleaning chemicals.
 Maintenance
Special attention should be paid to the quality of equipment
parts that are worn out quickly, e.g., brushes, screens, nozzles,
bearings, seals, conveyor belts, knives, and equipment surfaces
contacting flowing solids, e.g., grains. Equipment parts, requiring
frequent maintenance, should have easy and quick access.
 Standardization of Spare Parts
Equipment constructed of a relatively large number of
standardized common parts, requiring periodic replacement of a
small number of spare parts, is preferable. The use of the same
standardized parts, even in different equipment, reduces the
logistic cost of spare parts. Standardization facilitates
maintenance and repairs, and less expertise is needed.
 Quality of Materials
The appropriate quality of materials, used in equipment construction, is
important for avoiding interaction with the food and for equipment
stability. Quality factors for the materials are the total weight of
equipment (heavier equipment is usually more robust), the quality of
material workmanship (surface smoothness, type of welding), the
quantity of relatively expensive materials used (e.g., stainless steel,
Teflon, insulation), the antirust protection (e.g., double or electrolytic
galvanization, special paints), and the quality of basic constructional
elements, such as bearings and seals.

 Firmness/Durability
Food machines and equipment must be stable and firm (robust),
especially when they are strained due to frequent assembling and
dismantling for cleaning and maintenance or due to moving, e.g., in
flexible manufacturing. Robustness is especially required in seasonal
processing, during which large amounts of raw materials are processed in
a relatively short time and a significant part of the personnel is unskilled.
 Automation
Automation is applied successfully when food processing is
continuous, the output is high, the labor cost is significant, and
the factory is located in regions where industrial infrastructure
exists. However, automation increases the cost; the automated
equipment is usually more sophisticated and, therefore, more
delicate, requiring skilled personnel for adjustment and
maintenance or repairs.
 Operational Characteristics
• The operational characteristics are features facilitating the
operation of food processing equipment. In selecting processing
equipment, the following requirements should be considered:
reliability, convenience, safety, instrumentation, ergonomics,
efficiency, effectiveness, accuracy, and environmental impact.
 Reliability
• Since food is perishable, storage time is relatively short.
• Fresh products, such as fish, milk, fruits, and vegetables, must be
processed as soon as possible.
• This presumes high capacity and reliability of processing
equipment, and downtime and breaking down during processing
should be prevented.
• Equipment of plant utilities, participating indirectly in
manufacturing of food, such as steam generation, process
water, electricity, and refrigeration units, must also be
reliable.
• Reliability is also important in food factories delivering on the
basis of “just-intime” agreements. However, since even for the
best machines, there are limits in reliability, it is advisable to
always have machines ready to replace the brokendown ones.
• Certainly, in the production of large volumes of products, such
as tomato paste or frozen food, it is not possible to have spare
evaporators or freezers for replacement. However, spare units
to replace more delicate machines and instrumentation,
which are part of such large units, should be available (e.g.,
pumps, fans, compressors, sensors for quality control
 Convenience
• Convenience in operating equipment and machines is
especially important in cases where the personnel are less
skilled.
• the future growth of “middle management” in the factory
may shrink due to restructuring, since much of the work
formerly performed by supervisors and middle managers is
now superfluous and the operation of machines is entrusted
to less skilled individual workers.
 Safety
• Special care must be devoted to protect personnel working with machines that
have bare moving parts, such as cutting machines, fans, and milling and forming
machines.
• In all cases, machine guarding to protect the operator and other employees in the
machine area must be foreseen.
• The guarding measures may include constructional measures, barrier guards,
two-hand tipping devices, and electronic safe devices (e.g., automated stopping
of machine in any human limb passes a certain limit of a safeguarded area).
• Conveying, transportations inside of processing units, insufficient cleaning of
processing installations, and proceedings of reparations are, according to the HSE,
(Health and Safety Executive) UK, the major causes of accidents in food factories.
• The majority of accidents are connected with food factory planning and
manufacturing organization matters.
• With respect to food equipment used, meat processing accidents are often in the
following branches: (a) Meat and fish processing (slicing, cutting/sawing,
deboning, grinding, etc.) (b) Forming and packaging (wrapping, deposing and
molding, bottling, thermoforming, etc.) (c) Moving machines including conveying
(especially belt conveyors near personnel) and vehicles such as forklifts
 Instrumentation
• Food machines and equipment operate more efficiently when
processing conditions are controlled continuously.
• This may require sophisticated instrumentation.
• The recent trend is, in addition to the usual indicating
instruments, installed directly on the machines/equipment, to get
all the process information on screens through computers.
• This also helps in developing CAD and CIM programs in food
manufacturing. Optical weight instruments, for example, are very
useful in combination with robots.
• Equipment that can be fully automated through connection to
computers may also be “telecontrolled” (operated from a
distance), which is important in sophisticated continuous
processing (e.g., edible oil manufacturing and milling) and in
manufacturing of a number of special foods with the minimal
possible contact of personnel with the products (e.g., baby foods).
 Ergonomics
• Ergonomics (human engineering) is important in operation and
maintenance of food processing equipment and machinery.
• In ergonomics, the relation between the
dimensions/capabilities of the machines and the human
dimensions/capabilities is important.
• Generally speaking, operation and repair of machines should
require the minimal possible human effort (force).
• Furthermore, it should be noted that women usually have only
two-thirds of the force of men.
• Human force depends on age and training.
• Correct ergonomics is also important in jobs in which constant
human concentration is required, such as in several quality
control tasks (e.g., working in a sorting machine, control of final
packaging).
 Efficiency
• A usual requirement of food processing equipment is that
food processing should be accomplished in the shortest
possible time.
• Long-time contact of the food with air, high temperature,
humidity, and, in some cases, sun may reduce its quality
(time-dependent microbial, enzymatic, and chemical changes
of food).
• Processing may also reduce food quality.
• Thus, food quality increases the efficiency requirements of
food processing equipment.
• Slight overdimensioning of processing units is useful.
 Effectiveness
• In food manufacturing, the process requirements must be achieved, as
in sterilization, where the preset time–temperature values must be
reached.
• The same is also true for the case of drying, in which certain
temperature–drying time conditions must be applied, as well as the
final product water activity.
• Chemical peeling of foods is another example of defined process
conditions.
• Therefore, processing equipment must be operated effectively,
especially in preservation processes.
 Accuracy
• Many food processing operations do not require high accuracy in
industrial practice.
• However, in most packaging operations (e.g., bottling), in weighing, and
in confectionery processing, high accuracy is required.
• High accuracy is also required when robots are involved in food
processing.
 Environmental Impact
• “Environmentally friendly” machines and processing equipment
are required mainly for legal reasons, but also for reducing the
adverse effects on the health of people working in the food
processing plant.
• Environmental burden includes equipment noise, odor, and
effluents (water and air).
• Therefore, in selecting various machines and equipment for food
plants, the requirements of equipment operation under
environmental constrains must be met.
• The noise when personnel is working several hours per day near
chutes, noise of equipment conveying and filling cans and
bottles, as well as noise due to a large number of water jet
cutting instruments are examples requiring hearing protection of
the employees, as they may exceed 80 dB.
 Testing of Equipment
• Standard equipment is normally guaranteed by the
manufacturers/suppliers and usually needs no testing of its
performance before installation in the food processing plant.
• However, novel or complex equipment may need some form of
testing, either in the pilot plant (small units) or in the processing
plant.
• Testing procedures for various process equipment have been
published by the American Institute of Chemical Engineers (AIChE
1960–1990).
• The following process equipment is covered: centrifugal pumps,
rotary positive displacement pumps, centrifuges, evaporators,
dryers, continuous direct heat dryers, heat exchangers, particle size
classifiers, batch pressure filters, mixing equipment (impeller type),
solids mixing equipment, paste and dough mixing equipment, and
plate distillation columns.
• As an example, the testing of a rotary positive displacement
pump (Newtonian fluids) involves the following: definitions
and description of terms (density, viscosity, Reynolds number,
pressure drop, capacity, power, efficiency); instruments and
methods of measurement; test procedure, test conditions,
test data, and performance criteria; acceptance test;
computation and interpretation of results; performance
characteristics (power, capacity, efficiency versus total
pressure drop).