Many people like to buy a large barrel of oil, and we often think that the shelf life written on the packaging of edible oil is 18 months or longer. During this period, the quality of the oil is good.
But in fact, edible oil is not safe even if it is within the shelf life after being opened!
So, how long can the cooking oil be stored after it is opened?
According to 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 in the market under specified conditions. The 18 months refers to the shelf life of the edible oil before it is opened, and once 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, the degree of difficulty of deterioration, from easy to difficult are: 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.
Now most of the edible oils on the market are added with antioxidants, commonly used “tert-butyl hydroquinone” (TBHQ) and “dibutyl hydroxytoluene” (BHT).
Edible oil added with antioxidants can be stored for a longer time after opening, but there is no research conclusion for how long it takes.
Under normal circumstances, it is recommended that everyone uses it within 3 months.
Storage environment
Checking the trademark of edible oil, it will remind consumers that the storage conditions are: store in a cool, dry place, and airtight storage in the dark, 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 bottle cap is tightened after use, the contact between air and oil cannot be isolated. The area in contact with oxygen and the 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 put the oil drum on the side of the stove after cooking. It is wrong to do so. The high temperature environment will greatly accelerate the oxidation and rancidity of the cooking oil.
If you find that the oil has become rancid, do not continue to consume it. During 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.
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