ABSTRACT
It is well known that whatever their kind and origin,
fats and oils have a limited stability. During storage
they undergo various deteriorative reactions that
reduce their nutritive value and also produce volatile
compounds, giving off unpleasant smells and tastes. In
general, the term rancidity has been used to describe
the different mechanisms by which lipids alter in
nature, mechanisms that may have a biological or
chemical origin. Among the alterations of a biological
nature there are those produced by microorganisms
(bacteria, fungi, yeasts), which may be inhibited by the
addition of preservatives, and those produced by
enzymes, mainly hydrolytic rancidity or lipolysis. The
latter may be inhibited by thermal treatment, by
conservation at low temperature, or by reducing the
percentage of water. Alterations of a chemical nature are due to the
action of oxygen. Lipid oxidation reactions, known as
auto-oxidation, commonly occur in lipids with a high
content of unsaturated fatty acids and constitute the
most common deterioration of fats used in the food
industry. However, unsaturated fatty acids are not the
only constituents in foods that undergo oxidation.
Compounds that impart color and taste to foods, like
some vitamins, are also susceptible to oxidation, the
existence of double bonds in their structure being their
common denominator. It has been shown that the oxidation of unsaturated
fatty acids takes place through a chain reaction that
