Leaving Oil In Deep Fryers: Safe Or Not?

Deep frying is a popular cooking method for making fried chicken, French fries, and potato chips. It involves submerging food in extremely hot oil, which can reach temperatures of over 400 °F. While deep frying is a fast way to cook, it can be dangerous, with hot oil causing burns and starting fires. To prevent these issues, it's important to take safety measures such as keeping a kitchen fire extinguisher nearby and avoiding overcrowding the frying basket.

One common question about deep frying is whether you can leave the oil in the fryer after use. The answer is yes, you can leave oil in a deep fryer, but there are some important considerations to keep in mind. Firstly, make sure that your deep fryer has an airtight cover to maintain the purity of the oil before each reuse. Inspect the oil before reusing it to ensure it hasn't become cloudy and maintain its clearness. The type of oil you use also matters; vegetable oil is recommended as it has a high smoke point.

To get the most reuse out of your oil, it's best to filter it after each use to remove small food particles. Allow the oil to cool to room temperature, then carefully filter it through a sieve or strainer lined with muslin, kitchen paper, paper towels, or a coffee filter. Store the oil in an airtight container in a cool, dry place, separate from new oil. Used oil can generally be stored for up to 3 months if filtered and stored properly. However, if the oil starts smoking at a low temperature, becomes very dark and thick, or develops a rancid smell, it should be discarded.

How long can oil be left in a deep fat fryer?

Yes, you can leave oil in a deep fat fryer, but there are several factors to consider to ensure the oil maintains its purity and remains safe for consumption.

The recommended time to keep oil in a deep fat fryer is a few days to a few weeks, depending on how often the oil is used. Generally, once you've opened the oil, you should keep it for no more than three months. However, if the oil reaches its smoke point or develops an unusual smell, taste, or appearance, it should be discarded immediately.

To extend the lifespan of the oil, it is crucial to store it properly. After each use, the oil should be strained or filtered to remove any food particles, and the deep fryer should be cleaned. The oil should then be stored in an airtight container in a cool, dry, and dark place. Refrigerating the oil is recommended to maximise its longevity.

It is also important to consider the type of oil used. Oils with a high smoke point, such as vegetable oil, peanut oil, canola oil, and sunflower oil, are better suited for deep frying and can be reused multiple times if properly stored.

Additionally, the material of the deep fryer itself can impact the oil's safety. Modern deep fryers usually have airtight seals, which help maintain the quality of the oil during storage.

In summary, oil can be left in a deep fat fryer for a few days to a few weeks, but proper storage, filtration, and oil type are crucial factors in ensuring the oil remains safe and suitable for consumption.

What are the dangers of deep frying?

Deep frying is a popular way to cook food, but it can be dangerous. Here are some of the dangers of deep frying and how to avoid them:

Burns and Fires

Deep frying oil can reach temperatures of over 400 °F. At these temperatures, the oil is extremely hot and poses a risk of burning yourself or starting a fire. It is essential to take extreme safety measures when cooking with hot oil, such as keeping a kitchen fire extinguisher nearby and avoiding direct flames. Never leave a deep fryer unattended, as the food can burn and become a fire hazard.

Water and Oil Don't Mix

Water is highly dangerous when deep frying. When water comes into contact with very hot oil, it vaporizes instantly and turns into superheated steam. This can cause the oil to splatter, risking bodily injury. Never let water get into the hot oil or use it to clean the appliance while frying. If a grease fire occurs, do not use water to put it out, as this can cause the flaming oil to spread. Instead, use a kitchen fire extinguisher or cover the fryer with a metal lid.

Foodborne Illnesses

Deep frying must be done properly to ensure food safety. Food must be cooked to a safe minimum internal temperature to destroy bacteria and prevent foodborne illnesses. Always use a food thermometer to check the internal temperature of meat, poultry, or seafood. Refrigerate leftovers within two hours of frying to prevent rapid bacteria growth.

Oil Degradation and Contamination

Used frying oil can degrade and become contaminated over time. Oil has a "smoke point" at a specific temperature, after which it begins to break down and may develop an unpleasant odour or taste. Contamination can also occur if food particles are left in the oil, causing it to turn rancid and become toxic. To extend the life of your oil, strain and store it in a sealed, light-proof container in a cool, dark place.

Disposing of Used Oil

Do not pour used oil down the sink, as it can congeal and cause backups in your plumbing or sewer system. Instead, pour it into a sealable metal container and throw it in the trash. Alternatively, used cooking oil can be recycled in some areas to make biodiesel fuel or soap.

How to store oil for reuse

It is possible to store and reuse oil from a deep fat fryer, but there are several things to keep in mind to ensure the oil remains safe for consumption.

Firstly, the type of oil used is important. Vegetable oil is the most common type used in food outlets and is ideal for reuse because it has a high smoke point. The smoke point is the temperature at which the oil begins to smoke; it is dangerous to reuse oil after this point. Oils with smoke points above 230°C (450°F) include safflower, sunflower, corn, canola/rapeseed, and peanut/groundnut.

To get the most reuse out of your oil, it is recommended to filter it after each use to remove small food particles. Allow the oil to cool to room temperature, then carefully filter it through a sieve or strainer lined with muslin, kitchen paper, paper towels, or a coffee filter.

The oil should then be stored in an airtight container in a cool, dry, dark place, such as a refrigerator, for no more than three months. It is important to never pour hot oil into a container and to store used oil separately from new oil.

Before reusing stored oil, it should be inspected for any signs of deterioration. If the oil has become cloudy, started to foam, or developed a foul odour, taste, or smell, it should be discarded. Additionally, if the oil starts smoking before reaching the target cooking temperature, it should be discarded as there is a high risk of it catching fire during cooking.

How to clean a deep fat fryer

Step 1: Prepare the fryer for cleaning

Before you start, make sure you have the right equipment. You will need a container for the oil, a pan scraper or spatula, and kitchen paper or paper towels.

Turn off and unplug the fryer, and wrap its power cables in paper towels to protect against spills. It is very important that the fryer is not plugged in while you clean it.

Step 2: Drain the oil

Allow the oil to cool completely, then drain it into a sealable container. If you plan to reuse the oil, check that it isn't rancid or discoloured, and store it in a cool, dry place. Otherwise, dispose of the old oil safely.

Step 3: Clean the fryer basket

Remove the basket from the fryer and clean it with hot water and detergent. Scrub vigorously with a scouring sponge or brush to remove debris, then rinse and leave to dry on a dish rack.

Step 4: Remove debris and excess oil from the fryer

Blot up any leftover oil in the fryer with paper towels, then use plastic utensils such as spatulas or pan scrapers to remove debris. Avoid using metal utensils, as these may scratch the fryer.

Step 5: Clean the interior of the fryer

Fill a bowl with warm soapy water and place it next to the fryer. Use a sponge to clean the interior, using a circular motion. Then, fill the fryer with hot water and leave for 30 minutes to loosen stubborn grime.

Step 6: Clean the filters

If your fryer's filters are removable, take them out and soak them in hot soapy water, then wipe them with an absorbent paper towel. If they are not removable, use a small amount of detergent and a paper towel to remove excess oil and grime.

Step 7: Finish up

Empty the hot water from the fryer and rinse it out. Leave the interior to air dry, and wipe down the exterior.

Step 8: Safety checks

It is important to ensure that the fryer is completely dry before using it again. Blot with paper towels to speed up drying.

Maintenance

To make cleaning your deep fat fryer easier, wipe up any oil splashes from the exterior with paper towels as you go. Regularly change the oil if you use your fryer frequently, and always follow the instructions in the fryer's manual.

What type of oil is best for deep frying?

When choosing an oil for deep frying, it's important to select one with a high smoke point. The smoke point is the temperature at which an oil will start to smoke, and this is important because heating oil past its smoke point will cause it to impart a burnt flavour to your food. It can also be dangerous, as it may start a fire.

Most foods are deep-fried at temperatures of around 350-375°F (176-190°C). This means that, ideally, your chosen oil should have a smoke point of at least 400°F.

Oils with a high smoke point include:

• Safflower oil
• Sunflower oil
• Canola oil (also known as rapeseed oil)
• Peanut oil (also known as groundnut oil)
• Corn oil
• Avocado oil
• Grape seed oil
• Vegetable oil
• Olive oil
• Soybean oil

Some sources recommend canola oil as the best option for deep frying, as it is widely available, affordable, has a high smoke point, a low level of saturated fat, and a neutral flavour.

Frequently asked questions