Messi Biology states that when we pour oil into a hot pan in the kitchen, ready to cook a delicious meal, few people realize that behind a bottle of clear, aromatic edible oil lies a series of intricate purification processes. Magnesium Oxide (MgO) is the indispensable “invisible purifier” in this process. Its core mission is to precisely adsorb free fatty acids (FFAs) from edible oil, building a dual defense line for food safety and taste at our dining tables.
To understand the role of magnesium oxide, one must first understand what free fatty acids are and why they are “unwelcome guests” in edible oil. The main component of edible oil is triglycerides, a stable substance that provides energy for the human body. However, during the planting, pressing, and storage of oil crops, triglycerides decompose due to enzymatic hydrolysis, oxidation, and other factors, producing free fatty acids. These substances not only give the edible oil a sour, disagreeable odor but also lower the oil’s smoke point, causing it to produce smoke and harmful substances more easily during cooking. From a storage perspective, edible oil with high FFA content accelerates towards rancidity, shortening its shelf life. Therefore, removing free fatty acids is one of the core tasks in the edible oil refining process.
Magnesium oxide has become the “main force” for this task due to its unique chemical properties and adsorption mechanism. Magnesium oxide is an alkaline oxide, while free fatty acids are acidic substances. When the two meet, an acid-base neutralization reaction occurs, generating magnesium salts of fatty acids (magnesium soaps) that are insoluble in oil. These magnesium salts suspend in the oil as tiny particles, which can be easily separated through subsequent filtration or centrifugation processes, thereby achieving highly efficient removal of free fatty acids. At the same time, magnesium oxide possesses physical adsorption capabilities; its porous surface structure can incidentally adsorb some pigments, gums, and other impurities in the edible oil, making the finished oil clearer in color and purer in texture.
Compared to traditional adsorbents like activated carbon and silica gel, magnesium oxide offers significant advantages in edible oil purification.
- High Efficiency: One part of food-grade magnesium oxide can quickly neutralize multiple parts of free fatty acids.
- Gentle Process: The reaction is gentle and does not destroy nutrients such as unsaturated fatty acids and Vitamin E in the edible oil.
- High Safety: The purity of food-grade magnesium oxide meets national food safety standards. The generated magnesium salts are non-toxic and harmless, and because they can be completely separated, they leave no residue in the oil.
- Low Cost: The production process for magnesium oxide is mature, and its price is far lower than some high-end adsorbents, effectively reducing costs for edible oil companies.
In actual edible oil production flows, the application of magnesium oxide is flexible. In the crude oil refining stage, companies precisely calculate the ratio of magnesium oxide powder based on the FFA content of the crude oil. It is fully mixed and stirred with the crude oil, with reaction temperature and time carefully controlled. Once the neutralization reaction is complete, impurities like magnesium salts are removed via a plate-and-frame filter press. The oil then undergoes deodorization, decolorization, and other subsequent steps, finally resulting in refined edible oil that meets national standards. It is worth mentioning that for some specialty oils with high acid values, such as rice bran oil and tea seed oil, the neutralizing adsorption effect of magnesium oxide is indispensable, allowing crude oil that originally exceeded acid value standards to be “reborn” and meet edible standards.
Naturally, the application of magnesium oxide is subject to strict regulations. Magnesium oxide used in the food industry must be food-grade; the content of harmful impurities such as heavy metals and arsenic must be controlled within an extremely low range. Furthermore, the dosage must be precisely calculated to avoid abnormal pH values in the edible oil caused by overuse. Relevant companies also test every batch of finished oil during production to ensure that indicators such as free fatty acid content and purity comply with national standards.
From the oil crops in the field to the clear oil on the dining table, magnesium oxide plays the role of a critical “purification bridge.” Through silent chemical reactions, it helps us eliminate “hidden dangers” in edible oil, guarding the flavor and safety of every meal. As food processing technology continues to advance, the application scenarios for magnesium oxide are expanding. In the future, it will play a role in even more food purification fields, becoming an important guardian of our dietary safety.