In today’s health conscious world, there is a growing interest among consumers about the nutritional quality of the oils they take in: that is the fatty acids that they contain (Simopoulos, 2008, 2016). Vegetable oils which are widely used in cooking and food preparation are generally believed and thought to be a common cause of hypertension and are casually linked to increases
in cardiovascular diseases. This notion and perception is not entirely true. Vegetable oils contain different proportions and types of fatty acids (FAs); saturated and unsaturated, which have significant effects on health (Dorni et al., 2018).
What are Fatty Acids (FAs)?
Fatty acids are long chain hydrocarbons with a hydrophilic carboxylic acid group on one end and a hydrophobic methyl group on the other. Fatty acids can be classified as saturated or unsaturated fatty acids (Dorni et al., 2018).
Saturated fatty acids, typically solid at room temperature, have single bonds between carbon atoms, making them more stable and less likely to form harmful products when heated. They are commonly found in animal products like butter, lard, coconut and palm oils. Saturated FAs have been linked to increased cholesterol levels and cardiovascular risk when consumed excessively.
Some saturated fatty acids commonly present in cooking oils are Lauric, Myristic, Palmitic, and Stearic acids (Dubois et al., 2007).
Unsaturated fatty acids on the other hand are liquid at room temperature, contain one or more double bonds and are more sensitive to heat and light making it easy for them to spoil. Unsaturated fats are commonly found in nuts and seeds oils like avocado, sunflower, palm, palm kernel, olive and groundnut. Unsaturated fatty acids support heart health, aid brain function and regulate inflammation. Among the common saturated fatty acids present in cooking oils are Oleic, Linoleic, Gamma linoleic and Alpha linoleic fatty acids (Dubois et al., 2007).
The advances in technology have enabled researchers to find out the fatty acid profiles of these oils used commonly in homes for day to day cooking activities.
Some cooking oils and the fatty acids they contain
Out of the different types of cooking oils available on the market, oils with high saturated fatty acids content are recommended. Saturated Fatty acids are mostly found in oils like coconut oil and palm oil. These FAs are often criticized because they can raise low-density lipoprotein (bad cholesterol), which can increase the risk of heart disease (Mensink et al., 2003). Even though some new studies suggest that moderate consumption might not be as harmful as previously thought, it’s still wise to be careful with how much of these oils we use. Unsaturated FAs on the other hand are found in oils like olive and canola oil. These FAs are generally considered good for our health. They help lower cholesterol and can improve heart health. Olive oil, for example, is packed with oleic acid, a type of unsaturated FA that helps reduce inflammation and lowers the risk of heart diseases (Covas, De La Torre and Fitó, 2015). People who follow the Mediterranean diet, which uses a lot of olive oil, tend to have fewer heart problems. Omega-3 and omega-6 fatty acids are found in oils like flaxseed oil, soybean oil, and sunflower oil. Omega-3s are especially good for reducing inflammation and supporting heart health. Flaxseed oil, rich in alpha-linolenic acid (ALA), helps lower triglycerides and supports a healthy heart (Dorni et al., 2018).
How are fatty acids determined?
Thankfully, consumers don’t have to struggle to find which type of cooking oil to buy when next they want to make that favorite dish. Why? Because a countless number of researches and advances in science have made this information easy to access. Now we simply have to explore the market and look for the oils that are predicted nutritionally beneficial.
Scientists use several analytical techniques in determining the fatty acid compositions of vegetable cooking oils. Each technique with its unique function and working principles.
High Performance Liquid Chromatography - HPLC
High Performance Liquid Chromatography uses the technique of separating fatty acids based on their interactions with a stationary phase and mobile phase. When oil that has been derivatized into fatty acid methyl esters (FAMEs) is introduced into the column, the fatty acids in them are determined by their polarity to the stationary and mobile phases in the column. They could spend a longer time in the HPLC system due to their polarity to the silica gel or any other base stationary phase column or spend a shorter time due to their polarity with the mobile phase and be eluted faster. Their time spent on the column (retention time) analyzed by a UV detector would give the quantity and concentration of the fatty acids present as peaks. Using the retention times, peak heights and peak areas, the individual fatty acids can be determined. This technique though advantageous in detecting very low concentrations of fatty acids present and versatile in analyzing a wide range of fatty acids, is very expensive, complex and time consuming to use (Chernova et al., 2019).
Solid-Phase Micro Extraction - SPME
Another technique, Solid-Phase Micro Extraction, used also in the determination of fatty acids in cooking oils is an innovative sampling technique where a fiber coated with a stationary phase is exposed to the cooking oil and the fatty acids in the oil adsorbed onto the fiber. The fiber is then transferred into a gas chromatograph (GC) where the fatty acids adsorbed onto it are desorbed thermally into the GC system for analysis. This technique effectively captures volatile and semi volatile fatty acids without the need for solvents. This technique although a relatively simple one, has limited space capacity for analyzing samples, is less effective for analyzing nonvolatile compounds and its fiber degrades over time affecting its consistency and reliability.
Fourier Transform Infrared Spectroscopy - FTIR
Fourier Transform Infrared Spectroscopy involves exposing oil samples to infrared radiation causing specific vibrations in the fatty acids present in the oils according to the bonds present in the individual fatty acids. The resulting spectrum of the analysis provides the types and concentrations of the fatty acids present in the oils based on a wavelength specific infrared radiation absorption. FTIR analysis is rapid and can be completed in minutes, it is nondestructive and requires little preparation. It is rather limited in its ability to give quantitative data, has lower resolution making it hard to differentiate between closely related fatty acids, and has so much interference that its values are less accurate and reliable as compared to other techniques.
Gas Chromatography Mass Spectrometry - GCMS
Just like HPLC, fatty acids that are analyzed by Gas Chromatography Mass Spectrometry are converted into FAMEs and injected into the GC where they are vaporized by a gas through a column. As they pass through the column, the components are separated by their boiling points and their interaction with the stationary phase. The separated fatty acids then enter a mass spectrometer where they are ionized resulting in fragments that are analyzed to determine the structures and concentrations of the fatty acids present. GCMS is highly sensitive, specific, wide ranged and provides structural information about the specific type of fatty acid present. GCMS has a significant drawback to its potential use as it is very costly, not suitable for nonvolatile compounds and complex in its sample preparation (Á and Štefko, 2017; Zhu et al., 2019).
Gas Chromatography Flame Ionizing Detector - GCFID
The most robust of them all, GCFID. Even though it has limited detection and gives no structural information, is highly sensitive, cost effective and reliable. Similar to GCMS, Gas Chromatography Flame Ionizing Detector first converts the fatty acids in the oils into FAMEs. They are then injected into the GC where they are separated in the column based on their volatility and affinity for the stationary phase. These separated fatty acids as they exit the column are burnt in a hydrogen air flame in the FID and combust to produce ions that generate current which is proportional to the fatty acid present. The resulting signals are recorded as peaks in a chromatogram and the individual fatty acids identified from it (Chernova et al., 2019).
A study focused on determining the fatty acid profiles of coconut, groundnut, avocado, olive and sunflower oils used generally for cooking in the Ghanaian communities gave results represented in Table 1 below. GCFID was used in analyzing and determining the varying percentages of the specific fatty acids present in the oils.
Table 1
Oil | % saturated FA | % unsaturated FA | Health Impacts |
Olive | 5.5 | 94.6 | Heart healthy, anti-inflammatory |
Sunflower | 4.6 | 95.4 | Healthy cholesterol, heart healthy |
Coconut | 96.4 | 3.6 | Risk of cardiovascular diseases, increase cholesterol, increase inflammation |
Avocado | 7.8 | 92.2 | Heart healthy, anti-inflammatory |
Groundnut | 12.4 | 87.6 | Healthy cholesterol, heart healthy |
What oils would you be cooking with?
Heart healthy cooking oils.
Olive Oil
With a low saturated fat content and a high percentage of unsaturated fats, olive oil is excellent for heart health, reducing inflammation and supporting overall cardiovascular function.
Sunflower Oil
The high proportion of unsaturated fats in sunflower oil makes it beneficial for maintaining healthy cholesterol levels, contributing to a stronger heart.
Avocado Oil
Avocado oil's rich unsaturated fat profile helps improve heart health and reduce inflammation, making it a heart-friendly choice.
Groundnut Oil
Although slightly higher in saturated fats compared to other oils on this list, groundnut oil still has a high percentage of unsaturated fats, which supports healthy cholesterol and promotes heart health.
Cooking oils that cause hypertension and cardiovascular diseases.
Coconut Oil
With an extremely high saturated fat content, coconut oil is linked to higher risks of cardiovascular diseases, increased cholesterol levels, and more inflammation, making it a less healthy choice for the heart.
The next time you step out to purchase oil to make that dish, remember the unsaturated fatty acids and look for oils that are high in them.
REFERENCES
Á, A.B.Š.O. V and Štefko, T. (2017) ‘Faculty of Materials Science and Technology in Trnava Gas Chromatographic Determination of Fatty Acids in Oils With Regard To the Assessment of Fire Hazard’, 25(40), pp. 73–81.
Chernova, A. et al. (2019) ‘Ultra-performance liquid chromatography-mass spectrometry for precise fatty acid profiling of oilseed crops’, PeerJ, 2019(3), pp. 1–17. Available at: https://doi.org/10.7717/peerj.6547.
Covas, M.I., De La Torre, R. and Fitó, M. (2015) ‘Virgin olive oil: A key food for cardiovascular risk protection’, British Journal of Nutrition, 113(S2), pp. S19–S28. Available at: https://doi.org/10.1017/S0007114515000136.
Dorni, C. et al. (2018) ‘Fatty acid profile of edible oils and fats consumed in India’, Food Chemistry, 238(May), pp. 9–15. Available at: https://doi.org/10.1016/j.foodchem.2017.05.072.
Dubois, V. et al. (2007) ‘Fatty acid profiles of 80 vegetable oils with regard to their nutritional potential’, European Journal of Lipid Science and Technology, 109(7), pp. 710–732. Available at: https://doi.org/10.1002/ejlt.200700040.
Mensink, R.P. et al. (2003) ‘Effects of dietary fatty acids and carbohydrates on the ratio of serum total to HDL cholesterol and on serum lipids and apolipoproteins: A meta-analysis of 60 controlled trials’, American Journal of Clinical Nutrition, 77(5), pp. 1146–1155. Available at: https://doi.org/10.1093/ajcn/77.5.1146.
Simopoulos, A.P. (2008) ‘The importance of the omega-6/omega-3 fatty acid ratio in cardiovascular disease and other chronic diseases’, Experimental Biology and Medicine, 233(6), pp. 674–688. Available at: https://doi.org/10.3181/0711-MR-311.
Simopoulos, A.P. (2016) ‘An increase in the Omega-6/Omega-3 fatty acid ratio increases the risk for obesity’, Nutrients, 8(3), pp. 1–17. Available at: https://doi.org/10.3390/nu8030128.
Zhu, G. et al. (2019) ‘Profiling free fatty acids in edible oils via magnetic dispersive extraction and comprehensive two-dimensional gas chromatography-mass spectrometry’, Food Chemistry, 297(December 2018), p. 124998. Available at: https://doi.org/10.1016/j.foodchem.2019.124998.
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