Leaving Oil In Deep Fryer: Good Or Bad Idea?

Deep fryers are a common appliance in many kitchens, but they require careful maintenance to ensure the oil doesn't become rancid, which can lead to off-flavours and health risks. While it is possible to leave oil in a deep fryer, there are several factors that determine how long it can be left before it needs to be changed. These include the type of oil, the temperature it is heated to, and how well the fryer is maintained. For example, peanut oil, which is popular for deep frying due to its high smoke point and mild flavour, can be expensive and may not be suitable for those with peanut allergies. On the other hand, vegetable oil is a cost-effective option but may not have the same stability as peanut oil. To extend the shelf life of deep fryer oil, regular cleaning, filtering, and monitoring of oil levels are important. Oil should also be stored in a cool, dry place, away from heat sources, and labelled with the date of first use. While it is possible to reuse deep frying oil, it is important to strain it first and be mindful of the type of food being fried, as oil can take on the flavour of whatever is cooked in it.

Leaving oil in a deep fryer can make it go rancid

To avoid rancidity, it is important to cool the oil completely before storing it in a sealed container. Storing oil in the deep fryer, exposed to air, can cause it to turn rancid faster. Instead, it is recommended to strain the oil through a fine-mesh sieve or cheesecloth to remove any food particles, and then store it in a cool, dry, and dark place, such as the refrigerator.

Additionally, the type of oil used and the number of times it has been reused can also impact its lifespan. Oils with a high smoke point and those consisting mostly of saturated and monounsaturated fats are more stable at high heat and can be reused multiple times. However, reusing the same oil more than four times is not recommended, as it can increase cholesterol, create peroxide acids, cause cancer, and have other negative health impacts.

Therefore, it is important to pay attention to the quality of the oil and dispose of it properly when it starts to show signs of rancidity, such as a nasty or fishy odor, dark colour, or foaming.

Rancid oil is toxic

Secondly, consuming rancid oil can trigger digestive issues and distress. It can also deplete your body of essential vitamins, such as vitamins B and E.

Additionally, rancid oil can have an unpleasant taste and odour, making it unappealing and unsuitable for consumption.

To prevent oil from becoming rancid, it should be stored in a cool, dark, and airtight place, such as a sealed container in the refrigerator. Exposure to heat, light, and oxygen accelerates the rancidification process, so it is important to minimise these factors as much as possible.

Oil should be cooled and strained to be reused

It is important to note that frying oil takes on the flavour of whatever is fried in it. Therefore, it is recommended to fry similar items in previously used oil. For example, don't fry cinnamon doughnuts in yesterday's fish oil. The order of operations is also important. Vegetables tend to have the least impact on the oil, while breaded items, especially those with a fine coating of flour or cornstarch, tend to leave lots of particles that will continue to cook and burn, infusing the oil with a bitter flavour.

By following these steps and being mindful of what is cooked in the oil, you can reuse frying oil several times before disposing of it. However, it is essential to monitor the oil for any changes, such as a dark or dirty appearance, smoking before reaching frying temperature, foaming, or a rancid or musty smell. Once these signs appear, it is time to discard the oil responsibly.

Oil should be stored in a sealed container in a cool, dark place

To avoid rancidity, cool the oil to room temperature after use and strain it through a fine-mesh sieve lined with cheesecloth or a coffee filter to remove any food particles. Then, pour the oil into a clean, sealed container and store it in a cool, dry place, such as the refrigerator. Avoid storing the oil near the oven, fridge, or microwave.

It is also important to label the container with the date, the type of oil, and the number of times it has been used. Frying oil can be reused, but it should be discarded if it becomes dark or dirty, smokes before reaching frying temperature, foams at the top, or develops a rancid or musty odour.

Oil can be reused 2-8 times

Oil Reuse

Storing Oil

If you're planning to reuse oil, it's important to store it properly. First, make sure the oil is cooled down. Then, remove any food particles and debris with a skimmer. Next, filter the oil through a coffee filter or cheesecloth, and pour the strained oil into a container with a tight lid. Finally, store the container in a cool, dark place, such as the refrigerator.

Oil Quality

It's important to pay attention to the quality of your oil. If the oil becomes dark or dirty, smokes before reaching frying temperature, foams at the top, or develops a rancid or musty smell, it's time to dispose of it.

Health Considerations

While reusing oil can be a great way to save money and reduce waste, it's important to consider the potential health risks. Reusing oil multiple times can increase cholesterol, create peroxide acids, cause cancer, attack organ cells, and infect white blood cells. Therefore, it's recommended to reuse oil only a few times and to prioritise your health by disposing of it when it shows signs of degradation.

Frequently asked questions