The Rancimat method is considerably less costly, less labour-intensive but as accurate as the traditional active oxygen method (AOM) for the oxidation stability index (OSI) of natural fats and oils
Fats are an important component of our diet because they contain essential substances as polyunsaturated fatty acids.
Fats are also necessary for absorbing the essential fat-soluble vitamins (A, D, E and K) which are beneficial for health.
Therefore at least a minimal intake of fat is necessary.
Providing 9kcal of energy per gram, fats are a very concentrated source of energy for the human body.
Fat is primarily found in meat and dairy products but also in plants (eg, seeds, soybeans, olives, nuts).
Most foods contain some fat.
The main components of a basic unit of fat are three fatty acids individually bound to glycerol.
Especially animal fats and food containing animal fats (eg, lard, butter, meat sausages) as well as fats from tropical plants (coconut fat, palm fat) are rich in saturated fatty acids.
Whereas saturated fatty acids do not posses any carbon-carbon double bonds, monounsaturated fatty acids do have one.
Examples of vegetable oils rich in monounsaturated fatty acids are olive oil, rape oil and peanut oil.
These also contain high amounts of oleic acid.
When there is more than one carbon-carbon double bond present in a fatty acid then it is polyunsaturated.
Most vegetables contain polyunsaturated fatty acids.
Examples of oils rich in polyunsaturated fatty acids are safflower oil, sunflower oil, soybean oil, corn oil and cottonseed oil.
Fish also contain large amounts of unsaturated fatty acids.
Metrohm has a variety of proven methods and instrumentation for the determination of the quality of fats and oils at hand.
The oxidative stability of fats determined with Metrohm's 743 Rancimat.
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 oxidise 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.
Air is blown through the heated and thermostatted sample (50-220C) in order to oxidise 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 deionised 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.
Product information.
The 743 Rancimat is an instrument with two separate heating blocks.
The temperature of each block, containing four disposable sample vessels, can be controlled separately.
This setup allows the easy and time saving analysis of several different oils simultaneously.
In addition the 743 Rancimat allows predicting the shelf lives of natural oils and fats.
Get more information from Metrohm's free Application bulletins 204 and 141.
