The main objective of this work is to identify the fatty acid composition of various vegetable oils and fats available in market. Ten vegetable oils and fats were analyzed for its fatty acid composition by Gas-chromatography (GC-FID).
On vegetable oils, each position on the glycerol molecule may be esterified by a different fatty acid following plant patterns. The most common forms are the triacylglycerols (TAG), in which two or three kind of fatty acid moieties are present in the molecule. Both the physical and chemical characteristics of oils and fats are greatly influenced by the kind and proportion of the fatty acids on the triacylglycerols.
Fatty acids can be classified in classes as saturated, mono-unsaturated (MUFA) and polyunsaturated (PUFA) fatty acids. The predominant fatty acids present in vegetable oils and fats are saturated and unsaturated compounds with straight aliphatic chains. An even number of carbon atoms, from 16 to 18, with a single carboxyl group, is the most common. A number of other minor fatty acids may be present in same vegetable sources, including a small amount of branched chain, cyclic and odd number straight chain acids.
Materials and Methods:
Edible oil samples of five different varieties: sunflower oil (1 sample), refined soybean oil (2 samples), refined palm oil (1 sample), mustard oil (3 samples), refined vegetable oil (1 sample) and hydrogenated vegetable oil (Vanaspati 2 samples) were collected from local market.
Preparation of fatty acid methyl ester (FAME):
Concentrations of fatty acids were measured as their corresponding methyl esters following AOAC method. 50 mg of each sample was dissolved in 2 – 3 ml of diethyl ether, evaporated to dryness at 40 oC in a water bath under nitrogen stream. Then 2 ml of BF3 – MeOH (7%) reagent was added with 1 ml of toluene to each vial. Vials are sealed and kept in hot air oven at 100 oC for 45 minutes with occasional gentle shaking. Vials are allowed to cool to room temperature. 5 ml water, 1 ml hexane and 1 g of anhydrous sodium sulphate were added to each vial, shaken for 1 minute, allowed the layers to be separated. The top organic layers were collected in another dry vial and an aliquot of 1 ml was injected from each vial.
Analysis of FAME was carried out using Gas Chromatograph (GC model Varian). The GC was equipped with Flame Ionization Detector (FID) and Capillary column (Factor4, VF-1ms, Agilent). The GC method followed was: Injector temperature – 250oC, Detector temperature – 300oC, Flow – I ml/min, Carrier gas – N2. Column oven temperature program was started at 100oC to 150 oC @ 15 oC/min; to 200 oC @ 10 oC/min followed by 250 oC @5 oC/min with 12 min hold time.
Results and Discussion:
A total of 10 oil and Vanaspati samples were collected from local market. Their respective fatty acid composition are shown in Table-A and the total saturated fat% (SFA), monounsaturated fat% (MUFA) and polyunsaturated fat% (PUFA) are tabulated in Table-B.
It has been found from the study that Sunflower, Soybean and Palm oil samples contain fatty acids of chain length C16to C20. Whereas Mustard oil and Vegetable oil samples have fatty acids of chain length C16 to C22. Palmitic, Stearic, Oleic and Linoleic acids are common to all the oil samples. Trans fatty acids are identified in Hydrogenated Vegetable oils as expected.
Contributed by: Mr. Sourendra Nath Banerjee