Can peanut oil be reused? (3 signs of spoilage)

In this brief article, we will answer the question: can peanut oil be reused? We will also explain the shelf life of peanut oil, its recommended storage conditions, signs of bad peanut oil and how long peanut oil stays good.

Can you reuse peanut oil? 

Yes, you can reuse peanut oil. However, you should not reuse it. It is not recommended to reuse previously heated peanut oil. Exposing vegetable oils to heat when frying causes many chemical changes such as formation of free fatty acids, and physical changes such as increase in viscosity (1). The free fatty acids are formed as a result of the degradation process of unsaturated fatty acids,  lowering the nutritional value of the oil. The heating process also promotes oxidation of the oil, which is responsible for the change in flavor(2). 

Peanut oil also known as groundnut oil is a type of vegetable oil derived from peanuts. It usually has a mild or neutral flavor when made of fresh peanuts. If it is made from roasted peanuts the flavor and aroma become stronger.

Can peanut oil go bad?

Yes, peanut oil can go bad. Like all kinds of oils peanut oil also oxidizes with time and tends to develop rancidity.  However, if you store it in a cool dark place, the deterioration process can be diminished.

What is the shelf life of peanut oil?

Peanut oil, as many other vegetable oils, has a commercial expiration date. It is important to pay attention to the expiration date, and follow the manufacturer’s instructions on how to maintain it.

The shelf life of peanut oil greatly depends on the storage condition, but it is also affected by the fatty acid composition of the oil. High oleic peanut cultivars have been preferred by the industry due to an increase in shelf life (3), also influencing the nutritional quality and flavor. High oleic peanut oil can be stored for six months at 24 °C with a relative humidity of 50% without present perceptible changes (3). 

How to store peanut oil?

Peanut oil should be stored in a cool place, far away from light, and with minimum contact with air. Once opened, it is preferable to keep it refrigerated to maintain its quality, especially if it won’t be used soon.

How to tell if oil has gone bad?

Just like other vegetable oils, there are some visible signs that indicate that the peanut oil has deteriorated.

The signs that peanut oil has gone bad are:

Development of mold:

Oils are very shelf stable products but due to high levels of fats they are still at risk of fungal attack (4). A mold is very visible so you will know when to discard oil

Rancidity: 

Oils have a high level of fats and upon reaction with oxygen the fats get rancid. Rancid oil has a characteristic smell and flavor. If the oil gives off unpleasant odor it may be because it has gone rancid.

Change in color:

A visible change in color is a strong indicator of the oil’s deterioration, especially if it’s never been used.

How long does peanut oil stay good?

 The lifespan of a peanut oil depends on its fatty acid composition, and the storage conditions. If the oil was kept under the conditions specified by the manufacturer, it is within its expiration date, and it doesn’t present any off smell or change in color or viscosity, it is probably good to be used.

What are the health risks of consuming reused peanut oil?

The risks of consuming peanut oil are linked to the degradation products from the reactions that occur during the heating process. Many compounds are formed during frying, but one that raises more concerns is the oxidation of triglycerides, which can be easily absorbed and have potential effects on lipid metabolism (4).

The frying process increases the moisture content of the oil, and the water vapor produced favors the hydrolysis reactions in the oil (5), generating substances such as free fatty acids that are toxic to human cells (6). 

Conclusion:

In this brief article, we have answered the question “Can peanut oil be reused?”. We have also explained shelf life of peanut oil, its storage conditions, signs of bad peanut oil and how long peanut oil stays good. 

References:

1.       Bhardwaj S, Passi SJ, Misra A, Pant KK, Anwar K, Pandey RM, et al. Effect of heating/reheating of fats/oils, as used by Asian Indians, on trans fatty acid formation. Food Chem [Internet]. 2016;212:663–70. Available from: https://www.sciencedirect.com/science/article/pii/S0308814616309141 

2.       Zhao K, Shi L, Liu Z, Li J. Quality Analysis of Reheated Oils by Fourier Transform Infrared Spectroscopy BT  – Proceedings of the 2015 International Conference on Electromechanical Control Technology and Transportation. In Atlantis Press; 2015. p. 245–9. Available from: https://doi.org/10.2991/icectt-15.2015.47 

3.       Davis JP, Price K, Dean LL, Sweigart DS, Cottonaro J, Sanders TH. Peanut Oil Stability and Physical Properties Across a Range of Industrially Relevant Oleic Acid/Linoleic Acid Ratios. Peanut Sci [Internet]. 2016 Feb 15; Available from: https://doi.org/10.3146/PS14-17.1 

4.       Santos CSP, García LM, Cruz R, Cunha SC, Fernandes JO, Casal S. Impact of potatoes deep-frying on common monounsaturated-rich vegetable oils: a comparative study. J Food Sci Technol [Internet]. 2019;56(1):290–301. Available from: https://doi.org/10.1007/s13197-018-3489-z

5.       Choe E, Min DB. Chemistry of Deep-Fat Frying Oils. J Food Sci [Internet]. 2007 Apr 1;72(5):R77–86. Available from: https://doi.org/10.1111/j.1750-3841.2007.00352.x 

6.       Plötz T, Krümmel B, Laporte A, Pingitore A, Persaud SJ, Jörns A, et al. The monounsaturated fatty acid oleate is the major physiological toxic free fatty acid for human beta cells. Nutr Diabetes [Internet]. 2017;7(12):305. Available from: https://doi.org/10.1038/s41387-017-0005-x 

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