Oil Deep Frying: Can It Go Bad?

Cooking oil is a fundamental ingredient in kitchens around the world. It plays a crucial role in a variety of dishes, from fried foods to sautéed vegetables. But how long can you keep oil in a deep fryer before it goes bad?

The answer depends on several factors, including the type of oil, the food being fried, and the frequency of use. Oil in a deep fryer generally has a longer lifespan than oil in a skillet, and certain oils like canola, sunflower, peanut, and avocado oil have a higher smoke point, making them more stable for high-heat cooking.

To extend the life of your oil, it's important to store it properly when it's not in use. Keep unopened oil in a cool, dark place, and always allow it to cool before pouring it into a container for storage. You can also filter and refrigerate the oil to maximise its longevity.

Signs that your oil has gone bad include a darker colour, a rancid or foul odour, and foaming on the surface when hot. Oil can go rancid when it's exposed to oxygen, light, or high temperatures, so proper storage is key.

In summary, while there's no definitive answer to how long oil can last in a deep fryer, proper storage and filtration techniques can help extend its lifespan. By paying attention to the colour, smell, and behaviour of the oil, you can ensure that it's safe to use and hasn't spoiled.

How to store oil to extend its shelf life

To extend the shelf life of your oil, you must keep it away from light, heat, and oxygen. Here are some tips for storing your oil:

• Keep it in a dark place: Light breaks down the oil's antioxidants, causing the healthy parts to degrade faster. Store your oil in a dark cupboard or pantry, away from windows.
• Keep it cool: Heat can significantly decrease the life of your oil. Aim to store your oil in a cool location, preferably below 60 degrees Fahrenheit (15.5 degrees Celsius).
• Use airtight containers: Oxygen can cause the oil to oxidise and turn rancid. Store oil in airtight containers such as glass bottles or metal tins. Avoid plastic bottles, as they are not truly airtight and can result in an oily mess over time.
• Refrigerate: Placing oil in the refrigerator or freezer can extend its shelf life by up to two years. Note that the oil may become cloudy when thawing, but this is normal and will disappear once it returns to room temperature.
• Store unopened oil in a cool, dry place: Oil should be stored in a cool, temperature-controlled, dry, and clean environment. Keep it away from any heat sources.
• FIFO (First-In, First-Out): Implement a FIFO system to ensure older products are used first, reducing waste.
• Store horizontally: When storing drums of oil, place them horizontally to prevent moisture from getting inside.
• Keep labels visible: Position drums so that labels and instructions are clearly visible to ensure correct product use.
• No smoking: If stored in an area with foot traffic, install "No Smoking" signs for safety.
• Avoid outdoor storage: Storing oil outdoors can negatively impact its performance and reduce its shelf life due to potential water ingression and exposure to varying weather conditions.

Signs that oil has gone bad

Oil that has gone bad will exhibit several signs, indicating that it needs to be changed. Here are some key indicators that your deep fryer oil has gone rancid:

• Off-putting smell: Rancid oil will have an unpleasant, nasty, bitter, or tart smell. It may smell "old" or like crayons, or have a soapy or chemical odour.
• Unusual colour: The oil may turn darker and thicker, with a soapy appearance.
• Smoke: Bad oil may produce more smoke than usual.
• Taste: The oil may impart a burnt or stale taste to the food.
• Food particles: Excess batter, crumbs, or other food particles in the oil can cause it to degrade faster.
• Time and usage: Oil kept longer than the recommended period or used beyond its intended number of uses can turn rancid.
• Storage: Improper storage, such as exposure to light, heat, or air, can cause oxidation and rancidity.
• Temperature: Reheating oil to extremely high temperatures can make it go bad.

It is important to monitor these signs to ensure the oil is safe for consumption and to maintain the quality of your fried foods.

How to dispose of oil

Oil can indeed go bad in a deep fryer, so it's important to know how to dispose of it properly. Here are some detailed, direct, and instructive guidelines on how to dispose of oil, specifically from a deep fryer:

Allow the oil to cool:

It is essential to let the oil cool down to room temperature before disposing of it. This is a critical safety precaution, as hot oil can be dangerous and challenging to handle.

Choose a suitable container:

Select a container with a tight-fitting lid to store the oil. Suitable containers include empty cooking oil bottles, plastic milk jugs, cartons, coffee cans, or purchased grease disposal containers. Avoid using plastic bags, as they can leak easily.

Strain the oil:

Before storing the oil, it is advisable to strain it through a cheesecloth or coffee filter to remove any food particles. This step is crucial if you plan to reuse the oil later.

Seal the container:

Once you have poured the cooled and strained oil into the chosen container, ensure that the lid is securely sealed. This step is crucial to prevent leaks and spills.

Dispose of the container:

Place the sealed container with the oil in your household garbage. Alternatively, you can contact a local restaurant or recycling centre to inquire about adding your oil to their collection bin, especially if you have a large quantity. Some restaurants may even pay you for your used oil!

Compost vegetable oils in small amounts:

If you are using soy, corn, coconut, olive, or sunflower oil (100% vegetable oils), you can add small amounts to your compost pile. Earthworms will consume the cooking oil. However, avoid composting animal fats, as they can be harmful.

Mix with cat litter:

Another disposal option is to mix the oil with cat litter. Pour the oil into cat litter gradually and allow it to absorb. Once fully absorbed, place the oil-soaked litter into a sealable bag and discard it with your regular trash.

Recycle the oil:

Many cities and municipalities have specific recycling procedures for cooking oil. Check with your local government or recycling centre to find out the proper procedures for recycling used cooking oil.

Reuse the oil:

If you plan to reuse the oil for frying similar foods, strain and store it in a sealed container in the refrigerator for up to one month. Label the oil with the current date and inspect it before each use. If the oil smells bad, looks hazy, or has foam on the surface, discard it immediately.

Contact a waste management company:

If you have a large volume of oil to dispose of, consider contacting a waste management company that specialises in fryer oil recycling. They can provide collection containers and ensure proper disposal or recycling of the used oil.

Filtering oil to extend its life

Filtering oil is an important step in extending its life. Here are some tips to help you maximise the lifespan of your deep fryer oil:

Filter Oil Regularly

Proper filtration is crucial to extending the life of your fryer oil. Aim to filter the oil at least twice a day to maintain its quality and consistency. If you're using a commercial deep fryer, consider investing in an electric fryer oil filter machine to save time and effort. These machines can filter oil at high temperatures, so you don't have to wait for the oil to cool down before starting the process.

Skim the Oil's Surface

In addition to filtering, skim the top and sides of the fryer with a skimmer every 15 minutes to remove any loose food particles. This will help keep your oil cleaner for longer and improve the consistency of your fried foods.

Store Oil Properly

When not in use, store your oil in a cool, dark place away from direct sunlight and heat sources. Exposure to light and heat can accelerate oil degradation. Ensure the container is tightly sealed to prevent air and moisture from entering and deteriorating the oil.

Maintain the Right Temperature

High temperatures contribute to oil breakdown. Keep the fryer temperature consistent during cooking to minimise stress on the oil. Avoid excessive heat fluctuations, and turn off the fryer when it's not in use. Regularly calibrate your fryer's temperature settings to ensure accuracy and prevent overheating.

Clean Your Fryer Regularly

Keep your fryer equipment clean by regularly cleaning the interior, heating elements, and oil reservoirs. Remove built-up residues that can contribute to oil breakdown. Follow the manufacturer's instructions for cleaning and maintenance to ensure optimal fryer performance.

Other Tips

• Cover your fryer when not in use to prevent contamination.
• Only fill the fryer up to the recommended oil level to reduce waste and the risk of oil-related injuries.
• Test your oil regularly using oil testing kits to monitor its quality and breakdown.
• Educate your staff on proper oil handling, filtration, skimming, and temperature control.

Best oils for deep frying

When it comes to choosing the best oil for deep frying, there are several factors to consider, including cost, taste, and quality. Here are some of the best oils for deep frying:

Canola Oil

Canola oil is a popular choice for deep frying due to its neutral flavour, low saturated fat content, and balanced fatty acid profile. It is also more affordable compared to other oils, making it a cost-effective option. Canola oil has a smoke point of 350 to 400 degrees Fahrenheit, which is ideal for deep frying as it can withstand higher temperatures without burning.

Vegetable Oil

Vegetable oil is a blend of different plant oils, such as soybean, canola, corn, or sunflower oil. It is affordable, versatile, and has a high smoke point of 400 to 450 degrees Fahrenheit. This makes it suitable for deep frying as it can cook food thoroughly without breaking down. Vegetable oil also contains unsaturated fat, which is a healthier type of fat when consumed in moderation.

Peanut Oil

Peanut oil is a great option for deep frying as it has a high smoke point of 425 to 450 degrees Fahrenheit. It also adds a rich and nutty flavour to the food. However, it is important to note that peanut oil can be problematic for individuals with peanut allergies.

Sunflower Oil

Sunflower oil has a high smoke point of 440 to 450 degrees Fahrenheit, making it suitable for deep frying. It can withstand high temperatures without breaking down, ensuring the quality of the food is not compromised.

Cottonseed Oil

Cottonseed oil is another versatile option for deep frying due to its high smoke point of 420 degrees Fahrenheit and stability. It can be reused multiple times without compromising the quality of the fried food or the oil itself, making it a cost-effective choice.

Avocado Oil

Avocado oil has a mild and pleasant taste, with a high smoke point of 520 degrees Fahrenheit. It is generally more expensive compared to other frying oils, but its benefits can make it a worthwhile investment for certain commercial kitchens.

Frequently asked questions