Oil is never completely still.

From the moment it is produced, stored on supermarket shelves, and eventually heated in a frying pan, cooking oil continuously interacts with its environment. Oxygen, light, and temperature slowly alter its composition through chemical reactions.

If these reactions are not controlled, oil quality can deteriorate long before its expected shelf life.

When Oxygen Meets Oil

The main components of cooking oil are fatty acids. Some fatty acids readily react with oxygen in the air, initiating a process known as oxidation.

During the early stage, compounds called peroxides form. As the reaction continues, other compounds such as aldehydes and ketones appear—these are responsible for rancid odors and changes in taste.

Oxidation behaves like a chain reaction: once initiated, it can trigger further reactions, especially when oil is repeatedly heated at high temperatures.

Compared with many other vegetable oils, palm oil has a natural advantage. Its relatively higher saturated fatty acid content makes it more stable and resistant to oxidation.

Palm oil also contains natural antioxidants, particularly vitamin E compounds such as tocopherols and tocotrienols, which help slow down oxidative damage.

Synthetic and Natural Antioxidants

However, during the refining process—when palm oil is clarified and deodorized—some natural antioxidants may be reduced.

To maintain oil stability, the industry often adds small amounts of synthetic antioxidants such as:

TBHQ (tert-butylhydroquinone)

BHT (butylated hydroxytoluene)

BHA (butylated hydroxyanisole)

These substances work by neutralizing free radicals that trigger oxidation.

Although the amounts used are extremely small—typically 0.01–0.02% of the oil’s weight—they can significantly extend shelf life.

Recent research has also explored natural antioxidants derived from plants, including rosemary and green tea extracts, which contain phenolics, flavonoids, carotenoids, and vitamins.

Ultimately, maintaining oil quality is about controlling the rate of chemical reactions. With proper antioxidants, processing technology, and storage conditions, palm cooking oil can maintain its clarity, aroma, and safety from factory to kitchen. (*)

By Rosa Sepira, Chemical Engineering Student, Indonesian Palm Oil Institute of Technology.