Edible Oils Explained: Composition, Nutrition, and Storage Tips
Edible oils are an essential part of our daily diet, providing not only energy but also a range of nutrients that contribute to overall health. This document delves into the composition, nutritional value, storage, and health implications of various types of edible oils, including soybean, Rapeseed, palm, and peanut oils. It highlights the importance of understanding the chemical makeup of these oils and how their storage conditions can affect their quality and health benefits.
1. Main Components of Different Edible Oils
According to reports, in the USDA soybean germplasm collection, the highest oil content in seeds is 27.9%, which is relatively lower compared to sesame (60%). Soybean oil consists of five main fatty acids, accounting for 98.4% of the total oil composition: 10% palmitic acid (16:0, PA), 4% stearic acid (18:0, ST), 20% oleic acid (18:1, OL), 55% linoleic acid (18:2, Li), and 10% α-linolenic acid (18:3, LN). Research on soybean oil primarily focuses on improving its composition, increasing its content, and reducing harmful gases produced during its use by adding certain substances.
Rapeseed oil is rich in oleic acid, linoleic acid, and γ-linolenic acid. Specifically, many Rapeseed contain 75% oleic acid. All fatty acids in Rapeseed account for about 90% of the total fatty acid composition. The proportion of oleic acid in Rapeseed oil is higher than that in mustard oil and peanut oil, and the saturated fatty acid content in Rapeseed oil is lower than that in soybean oil and sunflower oil. Research on Rapeseed oil mainly includes the purification of oil components under different processes, as well as the retention of other nutrients (phenolic compounds), and reducing the content of 3-monochloropropane-1,2-diol esters (3-MCPDE) and glycine esters (GE).
Palm oil, derived from the fruit of the palm, typically contains 40% oleic acid, 10% linoleic acid, 45% palmitic acid, and 5% stearic acid.
Peanut oil is composed of more than 95% triglycerides (TAGs), including OOO, POL, OPO, OLL, and OOL. The total content of monounsaturated and polyunsaturated fatty acids in peanut oil is approximately 80%, while the total content of saturated fatty acids is about 20%. Among the unsaturated fatty acids, about 50% are monounsaturated fatty acids (oleic acid, C18:1), 30% are polyunsaturated fatty acids (linoleic acid, C18:2), and linolenic acid (C18:3) is almost undetectable. Nearly 10% of the saturated fatty acids are palmitic acid (C16:0), and the remaining 10% include stearic acid (C18:0), arachidic acid (C20:0), cetoleic acid (C20:1), behenic acid (C22:0), and lignoceric acid (C24:0).
2. Other Nutritional Values of Edible Oils
In addition to unsaturated fatty acids, Rapeseed oil also contains nine functional components that contribute to its antibacterial, anti-inflammatory, anti-obesity, anti-diabetic, anti-cancer, neuroprotective, and cardioprotective properties. These nine functional components are vitamin E, flavonoids, squalene, carotenoids, glucosinolates, indole-3-carbinol, sterols, phospholipids, and ferulic acid, which themselves or their derivatives have health-promoting characteristics. Reasonable intake of optimized Rapeseed oil produced by innovative refining processes (reducing trans fatty acid content, increasing vitamin E and coenzyme Q10 content) and rich in cardioprotective micronutrients represents a relevant nutritional approach to prevent the risk of cardiovascular diseases by improving cholesterol status and reducing LDL oxidation.
Red palm oil is one of the richest dietary sources of provitamin A (α-carotene and β-carotene) and is therefore used in programs to prevent long-term vitamin A deficiency. A unique feature of red palm oil is its particularly high concentration of phytosterols, which may account for 80-95% of the total phytosterols. Phytosterols are increasingly gaining attention for their health benefits.
Peanut seeds contain oil (47-50%) and protein (27-29%), as well as various nutrients beneficial to health, such as minerals, vitamin E, folic acid, niacin, antioxidants, and bioactive polyphenols, including flavonoids and isoflavones.
3. Research on Edible Oil Storage
Soybean Oil: Avoid Light Exposure
Soybean oil stored in the dark for 56 days showed an increase in peroxide value by 124±0.62% (p=0.006), while alternating with a 12-hour light cycle for 56 days, the peroxide value increased by 1473±1.79% (p≤0.001). When the temperature was raised from 22°C to 32°C and the headspace volume was increased from 67.0 ml to 283 ml, the impact on the oxidation state of the oil was minimal. Storing soybean oil in transparent bottles under household conditions may increase the risk of accelerated lipid oxidation caused by exposure to cool fluorescent light. In addition to lipid oxidation, vitamin A and D3 in the oil were found to be lost by 60-68% and 61-68%, respectively, after two months of exposure to natural light, and by 32-39% and 24-44%, respectively, under semi-dark conditions.
Rapeseed Oil: Avoid Light Exposure
Cold-pressed Rapeseed oil stored in amber glass bottles containing gel-pva-esa strips for 14 days showed the highest antioxidant potential, while oil without film strips had the lowest antioxidant potential. Freshly pressed Rapeseed oil was filled into colorless and green glass bottles and stored under light and dark conditions for six months. Due to light-induced processes, samples exposed to light oxidized more severely, with little observed effect from the bottle color.
Palm Oil: Store at Low Temperatures (4°C-8°C)
Current research on palm oil storage conditions and shelf life indicates that palm oil can be stored for 10 months at temperatures ranging from 4°C to 8°C.
4. Health Impact of Deep Processing or Spoilage of Edible Oils
Due to the high proportion of saturated fats in palm oil and the historical association between saturated fat intake and the risk of metabolic heart diseases, there have always been many opinions and controversial views on the adverse health effects of palm oil consumption, especially its adverse effects on coronary heart disease. Partially hydrogenated oils are the main dietary sources of trans fats, and esterified fats have largely replaced partially hydrogenated oils. Esterified palm oil can also have a negative impact on the metabolic parameters of the liver and white adipose tissue, glucose homeostasis, and the expression of cytokine genes.
Unsaturated fatty acids play an important role in immune system regulation, blood coagulation, nerve transmission, cholesterol metabolism, and the structure of phospholipids in the brain and retina membranes. However, unsaturated fatty acids are easily oxidized, leading to flavor deterioration and reduced shelf life of the oil. Oxidized oils or lipid oxidation products have been proven to have toxic effects on the growth and development of animals and humans. Feeding with oxidized soybean oil (OSO) during pregnancy and lactation showed that the intake of OSO by mothers during pregnancy can disrupt the intestinal barrier function of offspring by inhibiting the proliferation and differentiation of intestinal epithelial cells and reducing the activity of intestinal DNA methyltransferase.
Conclusion: Making Informed Choices About Edible Oils
The study of edible oils extends beyond their basic nutritional content to encompass their impact on health and their interaction with the environment. From the detailed analysis of their fatty acid profiles to the exploration of their storage and processing effects, this document underscores the complex nature of edible oils. It is crucial to consider these factors when choosing and consuming oils to maximize their health benefits while minimizing potential risks. The insights provided here can guide consumers and industry professionals in making informed decisions about the use and preservation of these vital dietary components. To further support your research, MetwareBio, a leading multi-omics company, offers comprehensive metabolomics and lipidomics services to enhance your study of edible oils.
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