Water supply for food processing
Practical Action
Detergents and sterilants
Detergents help remove the types of soils shown in Table 1 and different types are available for
different soils. They do not however, destroy bacteria or sterilise the equipment. Sterilants
destroy bacteria but do not help remove soils. It is therefore important, for proper cleaning, that
soils are first removed with a detergent and the surface of the equipment is then sterilised with a
sterilant.
Type of detergent
Action
Alkaline
Prevents mineral salt build-ups, removes fat.
Neutral
Used for surfaces that are damaged by other
detergents.
Acid Removes mineral salt scale.
Solvent
Removes fat.
Table 2: The types of detergent are shown in
The effectiveness of all detergents is increased by brushing and warming to 40-50°C (very high
temperatures might cause soils to burn onto equipment and should therefore be avoided). Fats
require temperatures above 70°C for removal. In practice the choice of detergent may be
limited and it is best to try a small quantity of what is available to make sure that:
it removes the soil
it does not corrode the equipment
it does not foam excessively
it does not leave a taint in foods used afterwards.
Sterilants are also called sanitisers or disinfectants. In practice, the most widely available
sterilant is chlorine solution (bleach or hypochlorite). Other types based on ammonia or iodine
may be found.
The advantages of bleach are that it kills a wide variety of micro-organisms, and it is cheap and
easy to use. The disadvantages are that it is corrosive, especially to aluminium, it may leave a
flavour/odour on the equipment if not properly rinsed and is less effective if soils are present on
the surface. It can also irritate skin and breathing, and is very dangerous if it contacts eyes or is
swallowed. It must therefore be handled with extreme care.
The strength of chlorine solution should be 100-200ppm. If household bleach is used (which
has about 5% sodium hypochlorite) it should be diluted by 1/250th to 1/125th to give 0.4-0.8%
bleach (or 100-200ppm). If bleach is not available it maybe possible to obtain sodium
hypochlorite powder and dilute it to obtain similar concentrations.
An alternative, for small pieces of equipment and glass or metal packs is to sterilise them by
heating. This can be done by immersing them in boiling water for 10-15 minutes, or setting up
a steam generator and using the steam.
Operator hygiene
The risk of operators transmitting diseases and infections through foods to the customers
depends on both the type of food and hygienic practices in the food processing unit. There is a
lower risk of infection in foods that are packaged and then heated (eg bottle juices, canned
foods). The foods that carry the greatest risk of infection from operators are those that are
handled after they are cooked (eg fried snack foods, cooked meats) and those that are not heated
before sale (eg sausages and other meat products, ice cream and other dairy products).
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