GC-FID App Note – Fat Profile of Edible Oils
Fatty Acid Analysis by GC FID of Common Cooking Oils
Daniel Iversen, R&D Chemist, Lucidity
Introduction
Cooking oils are used in a variety of foodstuffs, and they are used for frying and baking. Identification of the specific oils used in a process would be useful for health reasons and for cost savings. This study uses five different oils used for cooking and/or baking to identify the fingerprint of each of these oils. The study also shows the saturation level of these oils. The analysis was carried out by taking the oils and converting them into Fatty Acid Methyl Esters (FAMEs) and running on a Lucidity miniGC.
Experimental
The five oils were purchased from various sources at different times. They are:
- Coconut Oil
- Vegetable Oil
- Olive Oil
- Peanut & Soybean Oil
- Avocado Oil
Each oil was prepared for analysis by derivatization by adding 0.5 g of oil to a 150 mL erlenmeyer flask, adding 5.0 mL of refined xylenes and 10 mL of a 15% solution of boron trifluoride in methanol. All reagents used in the study were purchased from Reagents Specialty Chemicals and Solutions.
The solution was heated to 120 ℃ on a hot plate with stirring for 10 minutes. After, 10 mL of deionized water was added to the flask and allowed to cool to room temperature. Once cooled, the solution was added to a large sample tube and allowed to split into layers overnight. The top layer of the split was added to a 2 mL GC vial and injected into the miniGC. The program for the miniGC is outlined in Table 1.
No standard was prepared as this study was to identify the unique fingerprint of the individual oils in question. Using just the fingerprint one could determine the percentage of each carbon chain within the oil.
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Results
Each of the five oils tested showed a unique fingerprint on the chromatograms as outlined in Figures 1 through 6.
Each oil has a unique fingerprint based on the carbon chains within their triglycerides. Coconut oil has shorter carbon chains than most oils and is almost completely saturated, whereas Olive oil has longer carbon chains and is mostly monounsaturated at the C-18 peaks. The saturated carbon chains are shown in the chromatogram as a peak directly next to the saturated carbon chain peak.
Conclusion
Identifying oils through their unique fingerprint is possible with the use of the miniGC and converting the oils to a fatty acid methyl ester using a methylated solution of boron trifluoride. A secondary benefit is that the level of saturation of each carbon chain can be easily identified within the same chromatogram.
This is by no means intended as a comprehensive study on vegetable oils, but rather as a demonstration of the use of the miniGC for analyzing different vegetable oils.
More results from the miniGC can be found here: https://luciditysystems.com/products/minigc/minigc-results/
More information on the miniGC can be found here: https://luciditysystems.com/products/minigc/
To see the miniGC in operation go here: https://luciditysystems.com/products/minigc/minigc-interface/