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Many people like to buy a big barrel of oil. We often think that the shelf life written on the edible oil package is 18 months or longer, during which the quality of the oil is good.

But in fact, edible oil is not necessarily safe even if it is within the shelf life after it is opened!

So, how long can cooking oil be stored after it is opened?

According to the provisions of my country's "General Standards for Food Labeling": the shelf life of edible oil packaging of 18 months refers to the period during which it can be circulated as a commodity on the market under specified conditions.

The 18 months refers to the shelf life of the edible oil before it is opened, and once the product is opened, the shelf life of the edible oil has nothing to do with the 18 months on the trademark.

There are many factors that affect the shelf life of edible oil. The three most important ones are the type of oil, the antioxidants added to the oil, and the storage environment.

Type of oil

Different types of oils have different natural antioxidant components and fatty acids. These substances have different effects on the oxidation stability of edible oils. Therefore, different types of edible oils have different unsealed shelf life after being opened.

The five common edible oils are difficult to deteriorate, from easy to difficult: sunflower oil, soybean oil, corn oil, rapeseed oil, and peanut oil.

Antioxidants in oil

Studies have found that under normal living conditions, edible oil without antioxidants will generally reach the critical point of deterioration after 2 months of opening. In a few days, the unique "hala taste" of fat rancidity will appear.

In addition to the natural antioxidants contained in the edible oils mentioned above, synthetic antioxidants are generally added to edible oils.

Most edible oils on the market now have antioxidants added. Commonly used are "tert-butyl hydroquinone" (TBHQ) and "dibutyl hydroxytoluene" (BHT).

Edible oil added with antioxidants can be stored for a longer time after opening the lid, but there is no research conclusion for how long it takes.

Under normal circumstances, it is recommended that everyone eat it within 3 months.

Storage environment

Checking the trademark of edible oil, the above will remind consumers that the storage conditions are: store in a cool, dry place, dark and airtight storage, so whether the storage method is appropriate has a great impact on the shelf life and quality of the edible oil before and after opening.

The edible oil that has been opened will come into contact with air. Even if the cap is tightened after use, the contact between air and oil cannot be isolated. The area in contact with oxygen and the excessive number of openings will promote the oxidation and rancidity of the oil and accelerate it. If the edible oil deteriorates, the quality of the edible oil will decrease, and the "real" shelf life will be shortened.

In addition, for convenience, many people simply put the oil drum on the side of the stove after cooking. This is wrong. The high temperature environment will greatly accelerate the oxidative rancidity of the cooking oil.

If you find that the oil has become rancid, do not continue to consume it. In the process of oil rancidity, peroxides and free radicals which are harmful to the human body will be produced, which will accelerate the aging of the human body and increase the risk of tumors, cardiovascular diseases and other diseases.

Finally, a warm reminder: if you usually use less oil, it is still a good deal to buy a small bottle; if there are many people in the family, a large bottle of oil can be used up in less than one or two months, which is fine.