Q. Quality of edible oils - fats?
Various parameters are used for the assessment of the quality of fats and oils. Some of the important ones include determination of moisture content, colour, impurities, acid value, peroxide value and tests for the presence of adulterants in fats and oils. Let us review these parameters one by one, starting with the moisture content.
Moisture Content
Moisture content of the fats/oils is an important parameter and does not remain the same throughout the period of storage. More the moisture content, more prone is the fat to the process of hydrolytic rancidity. In this process, the triglyceride reacts with water and for each molecule of water involved, one molecule of fatty acid is released. When a molecule of fat reacts with three molecules of water, glycerol and three fatty acids are formed.
Thus, it is very important to control the moisture content in the oils/fats which otherwise would lead to the development of off flavours.
Colour
The colour of the oil is of considerable importance commercially and is an agreed standard of comparison. The colours of oils are usually declared in Lovibond units, and may be measured in an instrument designed for the same. The instrument includes a standard light source, glass ended cells of accurate length and the series of coloured glasses of yellow, red and blue colour. The colour of the oil is matched by a suitable combination of them. For an accurate analysis, it is important to keep the following points in mind:
• Number of matching glasses should be kept to a minimum.
• The oil must be clear and bright, filtration should be done if required.
• The oil should not be heated to an extent so that it affects the colour of the oil.