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Mineral deposits
Arise from food processing spills
Formed by:
deposition of insoluble hardness ions on
equipment – boilers, water softening/
conditioning plants
reactions between water-hardness ions and
ingredients in processing operation
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Mineral deposits
Form thick scales
Hard to remove
With time, these scales grow
If not removed, enhance microbial build-up
End effect:
Reduce heat transfer efficiency of:
Boilers, heat exchangers, evaporators and
pasteurises
Lower life of such equipment.
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Organic deposits
Arise from food processing spills
Include: Remains of food particles
Composed of carbohydrates, proteins, fats
Potential ports for microorganisms on plant
surfaces
Under favourable conditions, proliferate and
contaminate foods.
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Microorganisms
Food-spoilage and pathogenic organisms
Gain entry at different stages of processing
Intrude processing lines through:
Raw material
Water
Equipment and
Air
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Microorganisms
Food handler:
Good source of contamination, especially
with pathogens
Microorganisms more difficult to remove than
inorganic and organic soils
Safety of consumer depends directly upon
presence or absence of microorganisms in
processed foods.
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Removal of Soils
All soils can adversely affect quality of end
products
Necessary to remove these, if safe foods be
produced under hygienic conditions
Standard methods for cleansing food plant and
equipment involve:
Cleaning - using water and detergent solution
suited to soil and material of construction of
equipment
Sanitizing - using heat as steam or hot water
or chemical bactericides.
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2 Cleaning
Cleaning - operation in which soils deposited
during processing removed by any suitable
means
Terms used: cleaning and cleansing
Cleaning - making target surface free from dirt
or unwanted matter
Cleansing - generally used to remove infection
or illness
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2 Cleaning Methods
Cleaning - physical methods:
Dry cleaning
Wet cleaning
Dry Cleaning
Sometimes soils dry
Can easily be removed from all surfaces by:
Brushing
Scrapping or
Scrubbing
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2.1 Dry Cleaning
Soil deposits such as fats or food residues:
stick intimately to equipment
quite difficult to remove by physical methods
as brushing or scrubbing
In such cases wet cleaning, employing water,
used.
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2.2 Wet Cleaning
Water, by itself, an inefficient cleaner
Not very good at making things wet
Tension exists on water surface
Prevents water from coming into intimate
contact with either surface of material or dirt to
be removed
Overcome by use of cleaning agents or
detergents
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2.2 Wet Cleaning
Detergents:
Alter condition of water's surface
Reduce surface tension
Allows water to spread and wet soil
Besides reducing surface tension, detergents
perform two important functions in cleaning:
a. Dislodge dirts/soils
b. Disperse soil particles
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Functions of Detergents
a. Dislodge dirts/soils: Emulsify fatty dirts, dissolve
minerals, peptidize proteins, dissolve carbohydrates
b. Disperse soil particles: Dislodged particles of soil
remain dispersed, not re-attach to equipment surface
Dirt gets coated with detergent molecules
Detergent molecules align themselves on surface of
equipment, prevents further contact with equipment
surface
Water often contains inorganic impurities - hinder in its
action as a cleaning agent, and effectiveness of
detergents
In such cases water conditioning agents used.
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2.2.1 Detergents
Three major groups of dirts associated with
food processing industries:
Organic deposits
Mineral deposits and
Microorganisms
Each soil requires different cleaning agent
Successful cleaning operation depends upon,
among other factors, use of suitable detergents:
on each type of soil
on material of construction of plant surfaces.
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Properties of detergents
a Solubility - Must be readily soluble in water
Avoid possibility of depositing unwanted solids
b Wetability - Should adequately wet surface
interface
Dislodges soil
Should dissolve or disperse food materials released
c Emulsification - Detergent solution must
emulsify or disperse fats and oils
d Rinseability – be easily rinseable to avoid
residues remaining on equipment.
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Properties of detergents - contd
e Corrosiveness - Resulting detergent solution
must not attack contact surfaces
Avoid corrosion by correct selection of
detergent for particular material of construction
Stainless steel – minimum risk of corrosion
Remember:
Stainless steel not universally inert to
chemical corrosion,
alternative and cheaper materials of
construction might be used.
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Types of detergents
Basically three types: -
a. Acid detergents
b. Alkaline detergents
c. Surfactants or detergents composed of
surface active agents
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2.2.1.a Acid Detergents
Acid detergents have pH value below 3
Scale build-ups of inorganic salts best removed
with acid detergents
Acceptable acids:
Mineral acids - HCl, nitric, phosphoric
Highly corrosive to metals, unsafe to handle
Organic acids - Gluconic, sulphamic, citric,
tartaric acids - preferred
Gluconic and sulphamic acids widely used in
descaling heat transfer equipment –
evaporators, pasteurizers
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Acid detergents - Contd
Acid detergents usually compounded with:
synthetic detergents
non-ionic or sulphonate type
Both powdered and liquid forms available
Acid detergents safely used in conjunction with
iodophore in formulations for detergent
sanitisers
Thoroughly rinse all surfaces to which acidic
detergents applied
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2.2.1.b Alkaline detergents
Strong alkaline detergents have pH value
above 11
Weaker ones may have pH in the range of 8
and 11
Useful for removing organic soils
Have food emulsifying properties
Can dissolve solid food components such as:
Carbohydrates
Proteins and
Fats
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Alkaline detergents - contd
a. Sodium and calcium hydroxides
Used alone or with other cleaning agents
Important components of highly alkaline heavy-duty
cleaning compounds
Water solution powerful detergent with excellent
emulsifying and dispersing power
Serve as effective bactericides + detergents
when machine-parts and other equipment
soaked
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Alkaline detergents - contd
Hence, indispensable in heavy-duty cleaning
where high percentage of free caustic solution
required
Widely used in mechanical bottle washing
Obstacles:
Involve safety hazard – equipment,
personnel.
Corrosive to certain metals such as
galvanised steel, tin or aluminium
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Alkaline detergents - contd
b. Sodium metasilicate – Has good wetting,
emulsifying and deflocculating properties
Much less corrosive than caustic soda
Actually inhibits corrosion of aluminium and tin
Often used with a sodium polyphosphate -
mixture recommended where water hardness
exceeds 100 mg/L CaCO3.
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Alkaline detergents - contd
c. Sodium orthosilicate and sodium
sesquisilicate – Both compounds give highly
alkaline solutions
Powerful saponifiers
Readily attack greases and proteins
Sesquisilicates - less corrosive than
orthosilicates, but care necessary when using
either of these two solutions.
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Alkaline detergents - contd
d. Trisodium phosphate – Solution of
trisodium phosphate has excellent emulsifying
and dispersing properties
Water-softening agent
Used in conjunction with other detergents as a
water conditioner in general cleaning
compounds.
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Alkaline detergents - contd
e. Sodium carbonate or soda ash – Soda ash
as well as bicarbonate and sesquicarbonate of
sodium used both as water softeners and as
cleaners
Main use as buffering agents in several
cleaning compounds.
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2.2.1.c Surfactants - Detergents
composed of surface-active agents
Important function of a detergent - reduce
surface tension of water
All substances reducing surface tension in
water called surface-active agents or
"surfactants“
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2.2.1.c Surfactants - Detergents
composed of surface-active agents
Variety of surface-active agents available
Usually incorporated into detergent formulations
- have ability to penetrate under and into
soils/dirts to loosen them
At the same time, can keep oils/fats emulsified
until rinsing completed.
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2.2.1.c Surfactants - Detergents composed
of surface-active agents - contd
Molecular structure of surface-active agents:
Hydrophilic (water loving) head
Hydrophobic (water-hating) or lipophilic (fat
loving) tail
At surface:
hydrophobic tails of surfactant molecules
pushed out between water molecules
break strong electrostatic forces between
them
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2.2.1.c Surfactants - Detergents composed of
surface-active agents - contd
Result - surface weakened or, surface energy
of water reduced
Same time, hydrophobic tail attaches itself to
any film of oil or fat, dissolves or becomes part
of film
Hydrophilic head attached to water molecules
Result:
Oil and water held in firm bond in suspension
Create an emulsion.
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2.2.1.c Surfactants - Detergents composed
of surface-active agents - contd
Surface active agents classified by their ionic
charges into four types:
a. Anionic (-ve charge)
b. Cationic (+ charge)
c. Non-ionic
d. Zwitterion or amphoteric type
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2.2.3.a Anionic surfactants
Most popular types
Active ion in solution generally negatively
charged
Poor bactericides, used only for their detergent
properties
Have excellent dispersing and wetting powers
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2.2.3.a Anionic surfactants
Especially useful in removal of fatty acids or
inorganic soils
Sub-divided into:
a. Soaps
b. Alkylaryl sulphonates
c. Alcohol sulphates
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Anionic surfactants - contd
a. Soaps – Common soap typical example
Interaction product of caustic alkali and sodium
salt of a mixture of fatty acids
Ionic charge resides in carboxylate head -OOC.
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Anionic surfactants - contd
b. Alkylaryl sulphonates
Made from hydrocarbons (by-products of
petroleum industry) by reaction with sulphur
trioxide
Alkyl hydrocarbons not easy to sulphonate
Therefore, common practice to add a benzene
ring to facilitate the reaction
Benzene ring has no other significance than to
facilitate sulphation
Detergent behaviour depends on overall size
of the hydrocarbon.
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Anionic surfactants - contd
Tail: consists of long hydrocarbon chain that
confers to the molecule:
Wetability
Good surface activity and
Protein activity
Head: sulphonate or sulphate instead of
carboxylate
Negative charge on sulphonate head
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Anionic surfactants - contd
Detergent behaviour of sulphonates depends
on:
Overall size of hydrocarbon
- higher the carbon number and longer the
chain length, more the efficiency.
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Anionic surfactants - contd
c. Alcohol Sulphates
Formed by reaction of long chain fatty alcohols
with sulphur trioxide.
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2.2.3.b Cationic Surfactants
Positively charged active ions in aqueous
solutions
Act both as detergents and germicides
Used principally for their germicidal, fungicidal
and algaecidal properties
Powerful sterilants
Examples of cationic surfactants - quaternary
ammonium compounds (quats) - active in acid
solutions.
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2.2.3.c. Non-ionic Surfactants
Non-ionic surfactants neutral in aqueous
solutions
Not dissociated in solution
Virtually unaffected by water hardness
Powerful emulsifiers, used to emulsify colloidal
soils, being inert to the electric charge present
on colloids
Non-ionic surfactants have pronounced
foaming action, can lead to difficulties,
especially in disposal of detergent
contamination wastes.
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2.2.3.d. Amphoteric Surfactants
Have both negative and positive charges in
water.
These detergents are used for special purpose
in
Shampoo
Cosmetics
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Synergistic effect of surfactants
Some anionic surfactants exhibit synergistic
effects with other compounds - detergent
capability of mixture better than of individual
components
Mixing of anionic and cationic detergents be
undertaken with caution - such mixing can
reduce efficiency of both, with a consequent
deterioration in cleaning performance
Non-ionic forms can safely be combined with
anionic or cationic varieties.
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2.2.4.Water Conditioning Agents
Do not act directly on soils, but on water used in
cleaning
Such agents soften or condition water
Calcium or magnesium ions (hardness ions)
present in wash water interfere both with
cleaning and with particulate dirt suspension
In the first case, calcium ions react with soap
ions in wash water to form insoluble calcium
soap
This creates an unwelcome scum
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2.2.4.Water Conditioning Agents - contd
Secondly, calcium ions known to be strong
flocculating agents for particulate dirts
Act to flocculate dirt particles making it more
likely for them to redeposit on surfaces of
equipment
To counter effects of hardness ions, additives
that remove calcium and magnesium ions
added into detergent formulations
Ethylene diamine tetra-acetic acid, (-OOC
CH2) 2N(CH2) 2N(CH2COO-)2, (EDTA) and its
derivatives are among best water conditioning
agents.
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2.2.4.Water Conditioning Agents - contd
Certain phosphates have proved to be adequate
sequestering/chelating agents
Include sodium polyphosphate, tetrasodium
pyrophosphate and sodium tri- and tetra-
polyphosphates
Of these, sodium tripolyphosphate preferred
In solution, ionises to 5Na+ and (P3O10)5-
Phosphate ion complexes with Ca2+ of soap ion to
form soluble (CaP3O10)3 ion
So sequestering action of phosphate ion inactivates
calcium
Other sequestering agents: gluconic acid and its
sodium salt, trilon -N(CH2COO-)3.
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2.2.4.Water Conditioning Agents - contd
Mode of Action – Mode of action of water
conditioning agents generally complex formation
By complexing Ca and Mg ions, power of Ca and Mg
to interfere in washing/cleaning process destroyed
Ca and Mg immobilised or sequestered and
complexing compound called a sequestering agent
By their sequestering action, they aid in removal of
dirts and in subsequent dispersal of particulate dirt in
detergent solution
Hardness ion held stereochemically within chelates
In this manner, complex ions remain soluble and
stable, but inert.
