Dairy processing – an overview
contaminate products, and brass, iron or copper cannot be used because they promote rancidity
in milk fats. The layout of equipment within the room (Figure1) should allow food to move
between different stages in a process without the paths crossing. This reduces the risk of
contaminating finished products with raw milk. There should also be sufficient room behind
equipment for cleaning.
Cleaning and sanitation
Good sanitation is essential in all dairy processing. Equipment should be thoroughly cleaned
after each day’s production, using a cleaning schedule that indicates which equipment is to be
cleaned, who is responsible for cleaning it, how it should be cleaned, how frequently it is done,
and who is responsible for checking that cleaning has been done properly. All equipment should
be washed with hot water and a cleaning agent that is recommended for use with dairy products,
and then rinsed with chlorinated water. Equipment and surfaces should be allowed to dry in the
air, because wiping with cloths can re-contaminate them. If they are available, brushes with
coloured bristles are preferred because the coloured material can be seen easily if they are lost
in machinery or in the product. At the end of a working day, a slight ‘chlorine’ odour in the
processing room indicates that it has been properly cleaned. A summary of guidelines on hygiene
and sanitation is given in Technical Brief: Hygiene and safety rules in food processing.
Dairy processing creates large volumes of liquid effluents that contain milk fat, lactose and
protein, and this is highly polluting. Some wastes (e.g. whey from cheese-making) should be
used as animal feed or to make drinks or whey cheese, rather than being discarded down the
drain. Local regulations may require special treatment of dairy effluents and producers should
consult local authorities to plan proper effluent disposal. If mains drainage is not available, at
small scales of production a soak-away should be constructed in a place that cannot contaminate
drinking water supplies or pollute local streams or lakes.
In most countries, the legislation for dairy foods is more stringent than for many other types of
food. In addition to general regulations that govern labelling, weights and measures and hygiene
when handling foods, special regulations govern the manufacture and sale of dairy products that
are eaten cold without cooking. The legislation covers all aspects related to the operation of a
dairy and the microbiological and chemical quality of products. Dairy processors should contact
the responsible Ministry for copies of national regulations related to their products, and get
advice from a university or Bureau of Standards if necessary to clarify what the regulations mean.
They should also obtain a Health Permit from the Ministry of Health or Local Authority licensing
the premises to be used for food production, obtain a Manufacturing Licence from the Local
Authority or Ministry of Industry, and obtain Medical Certificates from the Health Authority to
certify that all workers are fit to handle food.
Quality assurance of milk supply
Because milk has a high risk of causing food poisoning, it is essential that processors pay great
attention to the quality of milk that they buy. Two types of danger exist: infections from the
living animal (e.g. Brucellosis) that are passed to the milk; and infections caused by
contamination of the milk. Contamination of milk in the milking shed can come from contact
with animal hides and faeces, poor quality water, dirty equipment and poor hygiene by milking
staff. To ensure that good quality milk is used, dairy processors should only buy milk from
reputable farmers or suppliers, and not rely on local street markets or middlemen. Milk should
be bought using quality specifications and agreements with farmers. It is important that dairy
farmers ensure that:
Udders are washed using a clean cloth and clean water before milking. They should boil
the cloth each day to sterilise it and dry it by hanging on a line in the sun.
All milking equipment should be thoroughly cleaned and disinfected and after each use.
People milking animals should wash their hands using clean water, because any bacteria
on their hands can contaminate the milk.