Fatty acids and antioxidants
Natural fats are mixed triglycerides of mostly saturated
and some unsaturated fatty acids. Common vegetable and
animal fats are coconut fat, palm fat, margarine and
butter. Oxygen can oxidize fatty acids in a multi-step
reaction that occurs in principle according to a radical
chain mechanism. The oxidation products formed by this
reaction (mainly formic acid) are volatile. Antioxidants
prevent the degradation of oxidation-sensitive vitamins,
amino acids and unsaturated fatty acids.
Determination of the oxidative stability
The determination of the oxidative stability of natural
fats is a standard quality control method
in the food industry. Metrohm's
743 Rancimat offers an easy and fast method to determine
the oxidation stability index (OSI)
of natural fats. The Rancimat Method is considerably
less costly, less labour-intensive but as accurate as
the traditional active oxygen method (AOM). Air is blown
through the heated and thermostatted sample (50...220
°C) in order to oxidize it. The stream of air then
carries over the volatile oxidation products (normally
formed at the end of the oxidation process) to a measuring
vessel containing deionized water. The readings of the
conductivity measurement can be plotted as a function
of the time required for the oxidation. The inflection
point of this oxidation curve is known as the induction
time which serves as a measure of quality of the fat
tested.
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Food
Analysis 
