Is oil safe to eat after the expiration date? (1+ risk)

In this article, we will discuss whether oil is safe to consume after its expiration date, how to identify spoiled oil and the risks of consuming spoiled oil.

There are many types of oil, however, the risks related to the consumption of spoiled oil are similar and may affect health negatively. Therefore, it is important to know how to handle oil properly to prevent it from spoiling. 

Is oil safe to eat after the expiration date?

Yes, it is safe to eat oil after the expiration date, if the oil has been kept unopened and stored correctly. Eating expired oil is not safe if the oil has signs of deterioration or spoilage, such as an unpleasant odour or discolouration (1).

On the other hand, consuming expired oil that has been improperly stored can have negative consequences on health, as improper storage of oil may lead to chemical spoilage and fungal development (1, 2).

Spoilage in vegetable oil is manifested especially by the altered odour and colour, which are caused by the oxidation of the fatty acids. Avoid consuming spoiled oil, as it can lead to diseases in the long term (3).

How long does oil last?

Oil lasts for several months to years, depending on the storage conditions, the packaging material used to store the oil and especially the source and processing of the oil, which determines the chemical composition of the oil (1).

The main reason for spoilage in oil is oxidation. The oxidative process can be caused by chemical and enzymatic reactions that are affected by environmental conditions.

In this way, specific conditions favour the oxidative reactions, such as heat, exposure to light and oxygen and contact with metals. Fungal activities may also lead to oxidation (1, 2).

According to studies, the shelf life of olive oil in an unopened and dark glass bottle at a cool temperature is 12 months, while the shelf life of olive oil at high temperatures and in a clear bottle is less than 3 months (1).

Why does the shelf life of oils vary?

The shelf life of oils varies due to the chemical composition of oils, which varies, depending on their type.

In the production process of oils, the vegetable sources, which are mostly seeds and grains, are crushed and extracted at high temperatures and in many cases, with the use of solvents.

This leads to the formation of free fatty acids and the extraction of compounds that may negatively affect the stability of the oil during its storage. For this reason, oils are refined before being commercialised (1).

Refining removes undesirable compounds but also some compounds that would favour the stability of oils, such as vitamins and antioxidants (1).

Oils naturally contain phytochemicals such as polyphenols, carotenoids, vitamins (such as vitamin E), and other antioxidant compounds. These compounds may reduce the rate of oxidative reactions and improve the shelf life of oils (4).

That is why extra virgin olive oil has a longer shelf life and greater stability than refined olive oil (1).

How to identify spoiled oil?

Spoiled oil can be identified by its unpleasant odour, which is characterised as oxidised or rancid. This odour is a result of oxidative processes, which generate volatile compounds such as peroxides, aldehydes and ketones (1, 3).

Off-flavours can also indicate spoilage. Bitterness and rancidity are off-flavours related to oxidised oils. Darkening of the oil may occur over time as well as other alterations in the colour (1, 3).

Changes in the consistency of the oil may result from heating processes, leading to oxidation and an increase in the viscosity, and colour, due to Maillard reactions (3).

The presence of fungal contamination can be identified by alterations in the odour and flavour (1).

What are the risks of consuming spoiled oil?

The risks of consuming spoiled oil are, as an immediate consequence, to have a foodborne illness and as a long term consequence, higher risks of developing inflammatory diseases (2, 3).

The long-term risks of consuming spoiled oil

Spoilage in oil is mainly due to oxidative processes, as previously mentioned in this article. The consumption of oxidation products, such as aldehydes and peroxides, in the long term can lead to inflammatory diseases.

Oxidation products, especially aldehydes, are very reactive and may interfere with many metabolic pathways in the cells, affecting its normal functions and leading to cell death (3).

Consuming oxidised oil is related to higher risks of diseases such as lung, colon, breast and liver cancers, and inflammatory processes in the body.

The immediate risks of consuming spoiled oil

The immediate risk of consuming spoiled oil is an intoxication by fungal toxins. Fungi are found in oils and can develop, under specific conditions, producing toxins which affect health negatively (2).

The ingestion of fungal toxins, or mycotoxins, is related to intoxication and liver cancer. Mycotoxins have carcinogenic and mutagenic effects and may affect many organs, including kidneys and the heart.

How to store oil to extend its shelf life?

To store oil and extend its shelf life, it is necessary to protect the oil from the environmental factors that lead to accelerated spoilage. They include heat, oxygen, humidity, light and contact with metals (1).

The following tips will help improve the shelf life of oil:

• Choose glass packaging to store oil, as it has a good barrier against oxygen and humidity
• Choose dark packaging to store oil to reduce the effect of light on oil oxidation
• Store oil in a dark and cool place and protect it from moisture
• Do not store oil in metal packaging
• Do not use metal utensils to handle oil
• Keep the oil unopened till use
• After opening, protect the oil from external oxygen and moisture by keeping the bottle sealed at all times 

What can you use instead of expired oil?

Instead of expired oil, you can use butter, margarine or lard. Expired oil should not be consumed. Oil is a source of lipids and can be substituted by other sources of lipids (1, 5).

Lipids have different properties, depending on the source and processing (1, 5). However, they are interchangeble. The best substitute for oil will depend on the application. 

However, the consumption of lipids should be moderate, independent from the lipid source, as excessive ingestion of lipids can cause negative effects on health (5) 

Conclusion

In this article, we discussed whether consuming expired oil is safe, the risks of consuming spoiled oils and why different vegetable oils have different shelf lives.

References