Fryer Oil: How Long Can You Keep It?

Frying oil can be reused several times, but it's important to know when to discard it. Each time frying oil is reused, it becomes more and more destabilized until it decomposes. There are several signs to look out for that indicate it's time to toss the oil: a dark or dirty appearance, foaming, smoking before it reaches frying temperature, or a rancid or musty smell. Other signs include cloudiness, an acrid aroma, or a hint of rancidity or anything that smells off.

Oil lifespan depends on type, frying frequency, and storage

The lifespan of frying oil depends on several factors, including the type of oil, frying frequency, and storage methods.

Type of Oil

Different types of oils have varying smoke points, which is the temperature at which the oil starts to smoke. Oils with higher smoke points, such as peanut oil, canola oil, or vegetable oil, are better suited for deep frying as they can withstand higher temperatures without breaking down. On the other hand, oils with lower smoke points, like extra-virgin olive oil, are not ideal for deep frying as they have a dominant flavour and can impart an unpleasant taste to the food.

Frying Frequency

The frequency of frying also affects the lifespan of the oil. Oil degrades with each use as it becomes more destabilized until it eventually decomposes. This process can be slowed down by carefully controlling the temperature during frying, ensuring it doesn't surpass the smoke point. Allowing the oil to cool completely before reuse and filtering it to remove impurities can also prolong its life.

Storage

Proper storage is crucial to maximize the lifespan of frying oil. Oil should be stored in a sealed, airtight container in a cool, dark place, preferably the refrigerator. Exposure to air, light, and high temperatures can accelerate the oxidation process, leading to rancidity. Additionally, frying oil can absorb flavours from the food cooked in it, so it's important to label and separate oils used for different types of dishes.

In summary, the lifespan of frying oil is influenced by the type of oil used, how often it is heated, and how it is stored. By choosing the right oil for deep frying, maintaining proper temperatures, and storing it correctly, you can extend the lifespan of your frying oil and get the most out of it.

Oil can be reused several times before disposal

To reuse frying oil, you need to strain it and store it in a lidded container in a cool, dark place. Once you’re done frying, let the oil cool completely in the frying vessel. Then, strain it into a clean vessel, like a glass jar or the original container it came in. It’s helpful to use a funnel and a cheesecloth set in a fine-mesh strainer here.

Next, label the container with the date, what the frying oil was used for, and the number of times it has been used. Then store in a cool, dark place until ready to reuse.

Frying oil takes on the flavor of whatever it originally fried, so keep this in mind for future frying projects. If you used oil to fry fish, it probably won’t be good for frying doughnuts next (but you can go in reverse).

If your oil has become dark or dirty, is smoking before it reaches frying temperature or foaming at the top, or has taken on a different smell (besides whatever foods you’ve fried in it) that is rancid or musty, then it’s probably time to dispose of it.

Oil should be strained and stored in a cool, dark place

Oxidation occurs when oil comes into contact with air, and this process is accelerated by high temperatures, metal alloys, surface exposure, and UV light. This is why it is important to store oil in a cool, dark place, such as a pantry or cabinet. Additionally, when oil interacts with water, it can cause the oil to taste tainted or acidic, especially if it is exposed to high temperatures and heating/cooling cycles.

To prolong the life of frying oil, it is important to control the temperature and avoid surpassing the smoke point, as this can cause the oil to break down and release substances that give food a bitter taste. Therefore, allowing the oil to cool completely and storing it in a cool, dark place is essential for maintaining its quality and preventing degradation.

By straining and storing the oil properly, it can be reused multiple times before it needs to be discarded. However, it is important to monitor the oil for any signs of spoilage, such as a dark or dirty appearance, smoking, foaming, or an unpleasant smell.

Oil takes on the flavour of the food cooked in it

Oil can take on the flavour of the food cooked in it, so it's not advisable to use the same oil for frying fish and then doughnuts, for example. It's a good idea to label used oils with what they were used to fry to prevent unfortunate flavour overlaps.

Oil can be reused a few times, but it's important to monitor its temperature to ensure it doesn't surpass its smoke point. When oil surpasses its smoke point, its fats start to break down, releasing a substance called acrolein, which gives burnt food its bitter taste. Frying with old oil will cause any type of food to taste acrid and greasy.

To prolong the life of your oil, it's best to store it in a cool, dark, airtight place. Cold temperatures may cause clouding, but this is nothing to worry about. You can also store oil in the refrigerator. If you're reusing oil, make sure you filter it first to remove any impurities, such as crumbs or sediment.

Each time you reuse oil, it gets more and more destabilised until it decomposes. Recycled oil can become cloudy or foamy, and develop an acrid aroma. Even if the oil looks and smells fine, it's best not to reuse frying oil more than three times before discarding it. Don't reuse oil that's been stored for more than one to two months.

Oil should be disposed of responsibly

Environmental Impact

Pouring oil down the drain can cause blockages in your home's plumbing and the entire sewage system. Clogged pipes can cause sewage backups. Oil that reaches waterways harms aquatic life and destroys ecosystems. It creates a slick on the water's surface, preventing oxygen from reaching aquatic organisms. Oil dumped on the ground can seep into the soil, contaminating it and harming plant life.

Fire Risk

Used cooking oil is highly flammable and can easily ignite. Improper storage can lead to fires.

Public Health Concerns

Oil poured down the drain can contribute to the spread of diseases by creating a breeding ground for bacteria.

Disposal Methods

There are several ways to dispose of used cooking oil responsibly:

• Store properly and then dispose of it along with other household waste. Ensure the oil is cool enough to pour into a sealable, disposable container, such as a plastic bottle or carton. Seal the container properly and include it in your food waste bin.
• Take used oil to restaurants for correct disposal.
• Contact a household hazardous waste disposal company.
• Use a grease disposal system, such as a grease trap, which is designed to intercept and retain fats, oils, and grease before they enter the wastewater system.
• Mix with other solid waste materials. Use absorbent materials like coffee grounds or paper towels to soak up and blot the oil, converting it into solid waste.
• Store in a glass jar. After frying, leave the oil to cool down, then transfer it to a glass container. Seal the container tightly. You can reuse this oil a couple of times.
• Make your own biodiesel. Used cooking oil is an excellent feedstock for producing biodiesel, a renewable, biodegradable fuel for diesel engines.
• Make soap. Soap-making is a popular way to repurpose used cooking oil. The process involves combining the oil with lye (sodium hydroxide) to produce soap.
• Reuse as a non-toxic insecticide or weed-killer. Used cooking oil can be sprayed onto plants to coat and suffocate insects, or to block sunlight from reaching weeds.

Frequently asked questions