DAIRY PROCESSING
An overview
Introduction
Milk is a valuable nutritious food that, if untreated, will spoil within a few days. However, there
are a number of preservation techniques that can be used at a small scale to extend its shelf life
by several days, weeks or months. Some of these processing methods also produce foods that
have different flavours and textures, which can increase the value of the milk when these
products are sold. This Technical Brief gives an overview of the types of dairy processing that are
possible at a small scale of operation. Details of the individual processing methods are given in
other Technical Briefs in this series: Pasteurised milk; Butter and ghee; Soured milk and
yoghurt; Cheese-making; Ice cream production and Dairy confectionery.
Other methods of milk processing, such as making dried milk powder, sterilised milk (Ultra-
High-Temperature or ‘long-life’ milk and bottled sterilised milk), canned (evaporated or
condensed) milk, or milk by-products such as casein, are not possible at a small scale because
of the very high costs of equipment and the specialist technical knowledge required.
Spoilage, food poisoning and preservation
Milk is not only nutritious for people, but also for bacteria. Because milk is a low-acid food,
bacteria are able to grow in it and contaminate any products that are made from it. If milk is not
properly processed or if it is contaminated after processing, bacteria can change the flavour,
texture or colour of dairy products, to spoil them and make them unacceptable for sale. Other
dangerous bacteria can grow in milk and cause food poisoning. Illnesses such as tuberculosis,
brucellosis and typhoid fever can also result from using poor quality milk or milk that is not
properly processed. All types of dairy processing therefore need careful control over the
processing conditions and good hygiene precautions to make sure that products are both safe to
eat and have the required shelf life. Processors must pay strict attention to hygiene and
sanitation rules throughout the process, from milking the animal to final sale of products. These
are described below and also in Technical Brief: Hygiene and safety rules in food processing.
Dairy building and facilities
It is important that a suitable room is set aside as a dairy and it is only used for processing. The size
of the room depends on the amount of milk being processed, but typically a small-scale unit that
processes 100-500 litres per day requires an area of approximately 50m2. A possible layout for a
small dairy is given in Figure 1.
The room should be hygienically designed and easily cleaned to prevent contamination of
products by insects, birds, rodents or micro-organisms. A panelled ceiling should be fitted rather
than exposed roof beams, which would allow dust to accumulate that might contaminate
products. There should be no holes in the ceiling or roof, and no gaps where the roof joins the
walls, which would allow birds and insects to enter.
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