|Training Programme for Women Entrepreneurs in the Food-processing Industry - Volume II (UNIDO, 1985, 286 p.)|
|Chapter 2 Vegetable Oil Extraction|
Edible oil is a valuable product that has universal demand for domestic use, as an ingredient for other local food production (for example bakeries and fried snackfoods), as a raw material for industrial use and as an export commodity (for food use, as body/hair oil and detergents). A major non-food use for oil is in soapmaking. Uses for different oils are summarised in Table 1.
Principles of Preservation and Methods of Processing
The principles of preservation are 1) to destroy enzymes in the raw material and contaminating microorganisms by heat during processing and 2) to remove as much water from the oil as possible to prevent microbial growth during storage. Oil therefore has a long shelf life due to its low moisture content. Proper packaging and storage conditions are needed to slow down chemical deterioration (rancidity).
The method used for processing depends on the type of raw material available. Raw materials can be grouped according to the part of the plant that contains the oil or fat (Table 1). The main difference in raw materials is the moisture content. Raw materials with a low moisture content include seeds and beans which are dried on harvest and some nuts. Coconuts are usually dried (to copra), but palm fruits, olive fruits and sometimes coconut are processed wet.
Only seeds, nuts and fruits that contain considerable amounts of edible oil are used for small scale oil extraction. Other types (for example maize) may contain edible oil but the quantities are too small for economic processing on a small scale. However not all oil-rich seeds and fruits have edible oil. Some contain toxins or unpleasant flavours and these are only used for varnishes, paints etc. and are not eaten. Others (for example castor oil) need very careful processing to make them safe for use as medicines. These are not suitable for small scale production.
PROCESS FLOW DIAGRAMS