Oils and fats are essential sources of energy in the human diet and significantly contribute to the sensory characteristics of food. Overweight (body mass index, BMI ≥ 25) and obesity (BMI ≥ 30) are classified as abnormal or excessive fat accumulation in the body, which can negatively impact health. These conditions may arise from a variety of factors, including individual predisposition, socioeconomic status, and environmental influences. Common causes include dietary habits, genetics, medication use, physical activity levels, urbanization, and mental health disorders.
Obesity is associated with various metabolic and cardiovascular diseases, as well as depression and other conditions. While medications can be used to control weight, they may have side effects. The key to weight loss is maintaining a healthy diet and engaging in regular exercise. Oils and fats are widely used for cooking, frying, and in various food formulations. The fast pace of urbanization has made fast food a popular choice due to its convenience and affordability. Greasy foods are not only prevalent in fast food establishments, but also commonly consumed in office meals, restaurants, schools, and even in many households.
Plant oils have gained importance in various industries, including food, cosmetics, pharmaceuticals, and biofuels. Globally, around half a billion tons of oilseeds and over 300 million tons of oil-fruits are cultivated, resulting in a yield of over 200 million tons of vegetable oil. These oils, obtained from seeds, fruits, or nuts of various plants, have been utilized for centuries due to their diverse compositions and beneficial properties. With the increasing demand for natural and sustainable products, there has been a significant focus on exploring the potential of plant oils.
Furthermore, plant oil serves as a viable alternative to animal oil, and research has demonstrated that plant oil, specifically unsaturated fats, is healthier compared to animal oil, which is predominantly saturated fat. Plant oils primarily consist of triglycerides, wherein glycerol molecules are linked to three long-chain fatty acids through ester linkages. Unsaturated fats typically contain double bonds, giving them a liquid form at room temperature, whereas saturated fats lack double bonds and have a structure that allows them to solidify at room temperature.
In recent decades, the importance of plant oils has significantly increased, leading to a doubling of global oil crop production over the past two decades. While many oils are used for non-food purposes, such as industrial applications, the industrial use of vegetable oils currently represents only a small portion, accounting for approximately 5% of total production, mainly for biodiesel production. Around 80% of edible oils are derived from plant sources, with temperate annual oilseeds contributing to approximately 60% of this total production.
Furthermore, soybean oil dominates this category, accounting for over half of the world’s vegetable oil production. The largest increases in average yield were observed in oil palm and rapeseed. Oils derived from various herbs and spices are primarily used for aromatic, medicinal, and other industrial purposes. Blending different vegetable oils can alter the fatty acid composition and result in higher levels of natural antioxidants and bioactive lipids in the blends, thereby enhancing the nutritional value and stability of the oils.
Plant oils can be obtained from multiple sources. For example, oils can be extracted from fruits such as avocados, olives, and coconuts. Nuts like macadamias, legumes including peanuts and soybeans, and seeds like almonds, cottonseeds, grapeseed, sunflowers, safflower, rice bran, soybean, and canola are common plant oils found in the market. Among them, oils derived from legumes and seeds are the most affordable and commonly utilized.
There are more than 200 plant species whose seeds are utilized for producing oil used in illumination, medicine, food, soap, and machinery lubrication. The oil content in the seeds serves as an energy reserve for germination, similar to starch. The oil is typically located in the endosperm tissue, cotyledon, or embryo, depending on the species. Various methods are employed for oil extraction, including organic solvent extraction, mechanical pressing, aqueous extraction, enzymatic extraction, and supercritical fluid extraction.
Modern extraction techniques now include fluid-phase partitioning, sorptive extraction, and membrane-based extraction methods. Typically, the seeds are initially crushed and then pressed in cloth bags, or they may be boiled in water and the oil skimmed off from the surface. Some chemical solvents, such as carbon disulphide, can be used for oil extraction. Cold pressing or a combination of heat and pressure may be employed to separate any albumen present and make the oil more liquid. However, when producing high-quality medicinal or culinary oils, no heat is involved in the extraction process.
To promote the use and advancement of plant oils, breeding efforts aimed at increasing yield and oil content are becoming increasingly important. This helps to enhance the nutritional value of vegetable oils and their suitability for specific industrial applications. However, despite the numerous benefits of plant oils, not all of them are suitable for consumption. Examples include castor, jatropha, neem, tung, and linseed (or flaxseed). These oils either contain toxic compounds or are used in cosmetics, pharmaceuticals, and manufacturing.
Plant oils are rich in various active compounds that offer health benefits. Edible vegetable oils primarily consist of triacylglycerols, along with lower levels of diacylglycerols, monoacylglycerols, free fatty acids, and minor components such as phosphatides, sterols, fatty alcohols, fat-soluble vitamins, and other compounds. However, the concentration of these compounds may vary depending on horticultural practices.
When consuming vegetable oils, it is important to note that the predominant fats in these oils are highly unstable. Not all oils are suitable for cooking, as they have different smoke points. Once an oil exceeds its smoke point, the levels of free fatty acids increase significantly, and the taste of the oil deteriorates. Vegetable oils, being polyunsaturated fats, can release DNA-mutating chemicals and neurotoxins when exposed to heat and oxygen. However, some plant oils can be consumed in their raw form, such as in salad dressings. Margarines and spreads nowadays are predominantly made from vegetable oils like safflower, sunflower, soybean, cottonseed, rapeseed, or olive oil.
In addition, vegetable oils are widely used in baking, particularly in baking and confectionery products. They are also common ingredients in cosmetics and personal care products, including skin moisturizers, hair care products, lip balms, soaps, and body washes. The bioactive compounds present in vegetable oils also make them valuable sources for medicinal oils and extracts, which can be used in the production of supplements.
Vegetable oils have industrial applications in the production of biofuels and lubricants. Lubricants derived from vegetable oils are used in various industries to lubricate machinery and materials. Both edible and non-edible plant oils can be converted into biodiesel, serving as a promising alternative fuel source for diesel engines. However, it is important to be cautious about the potential environmental issues associated with the overexploitation of cultivable land for biofuel production.
Efforts are being made to reformulate additives, chemically modify vegetable-based oils, and genetically modify oilseed crops to enhance their low-temperature properties and resistance to oxidative degradation. There is significant attention and research focused on genetic improvements in vegetable oils for both edible and non-edible applications to ensure that these products meet sustainability and environmental considerations.
Overall, plant oils offer a diverse range of benefits and continue to be an important resource in various industries and for our overall well-being.
Further reading:
Alonge, A. F., & Jackson, N. I. (2018, October). Extraction of vegetable oils from agricultural materials: a review. In Nigeria: Proceedings of the 12th CIGR Section VI International Symposium, held at the International. Institute of Tropical Agriculture, Ibadan, Oyo State, Nigeria.
Aluyor, E. O., & Ori-Jesu, M. (2008). The use of antioxidants in vegetable oils–A review. African Journal of Biotechnology, 7(25).
Aluyor, E. O., Obahiagbon, K. O., & Ori-Jesu, M. (2009). Biodegradation of vegetable oils: A review. Scientific Research and Essay, 4(6), 543-548.
Damude, H. G., & Kinney, A. J. (2008). Enhancing plant seed oils for human nutrition. Plant physiology, 147(3), 962-968.
Dubois, V., Breton, S., Linder, M., Fanni, J., & Parmentier, M. (2007). Fatty acid profiles of 80 vegetable oils with regard to their nutritional potential. European Journal of Lipid Science and Technology, 109(7), 710-732.
Fox, N. J., & Stachowiak, G. W. (2007). Vegetable oil-based lubricants—a review of oxidation. Tribology international, 40(7), 1035-1046.
Geow, C. H., Tan, M. C., Yeap, S. P., & Chin, N. L. (2021). A review on extraction techniques and its future applications in industry. European Journal of Lipid Science and Technology, 123(4), 2000302.
Harish, N., Kumar, K. A., Srinivas, D., & Kumar, S. (2017). Review on oil extraction techniques. International Journal of Agricultural Science and Research (IJASR), 7, 567-576.
Karaosmanoglu, F. (1999). Vegetable oil fuels: a review. Energy sources, 21(3), 221-231.
Maurya, A., Prasad, J., Das, S., & Dwivedy, A. K. (2021). Essential oils and their application in food safety. Frontiers in Sustainable Food Systems, 5, 653420.
