Mixing Old And New Oil In A Deep Fryer

Deep-frying at home is a messy, dangerous, and costly affair. One way to reduce the cost of deep-frying is to reuse the oil. However, reusing oil for too long can be detrimental to your health.

Reusing frying oil is generally safe, but there are some rules to follow. For instance, the oil should be strained and stored in a lidded container in a cool, dark place. Additionally, frying oil takes on the flavour of whatever it originally fried, so it's important to fry similar items in previously-used oil.

It's also important to note that not all oils are suitable for deep-frying. Oils with high smoke points, such as canola, sunflower, and vegetable oils, are best suited for high temperatures.

While frying oil can be reused, it should not be used indefinitely. Oil can become rancid, which can be identified by a cloudy appearance, a foamy texture, or a rancid smell. Reusing oil that has become rancid can lead to harmful health effects, including increased inflammation, cholesterol, and acidity levels. Therefore, it is recommended to change the oil for deep frying after a few uses, depending on the type of oil, the food being fried, and the maintenance of the oil.

How to tell if your oil is rancid

It's important to know when your oil is rancid, as using rancid oil can lead to serious health hazards. Rancid oil contains carcinogenic free radicals, which are absorbed into the food being fried.

• Smell the oil. If it has a bitter, soapy, or chemical smell, it's likely rancid. If you're not sure, pour a small amount into a teaspoon and smell it.
• Taste the oil. Take a small sip and suck on it. If it tastes harsh or bitter, it's rancid.
• Look at the colour of the oil. If it looks darker than usual, it might be rancid. Compare it to a fresh bottle of oil to see if there is a noticeable difference.
• Check for stickiness. If your bottle of oil feels sticky, this could be oil residue undergoing polymerization, an advanced stage of the rancidity process.
• Observe the oil for cloudiness or foam on top. If there are dark bits at the bottom, it's probably rancid.
• Pay attention to the flavour of your fried food. If it has a burnt or bitter flavour, it could be a sign that the oil is rancid.

Remember, if you're unsure, it's best to err on the side of caution and replace the oil.

Straining and storing oil

Step 1: Allow the Oil to Cool

Before straining and storing your oil, it is important to let it cool down completely. Turn off your fryer and let the oil sit until it reaches room temperature. Oil burns can be dangerous and painful, so it is important to wait until the oil is no longer hot before handling it.

Step 2: Prepare Your Straining Equipment

To strain the oil, you will need a fine-mesh strainer or sieve and a filter. A paper coffee filter or a flour sack towel can be used as a filter. If using a coffee filter, you may need multiple layers to ensure that the oil is properly filtered. Place the filter inside the strainer or sieve, and set it over a bowl or large glass measuring cup.

Step 3: Strain the Oil

Slowly pour the cooled oil into the filter. Stop pouring when you reach the last bit of oil that contains debris and sediment from frying. The oil will slowly pass through the filter and strainer, leaving behind any food particles and impurities. You may be surprised by how much oil is recovered after straining!

Step 4: Choose an Appropriate Container

When choosing a container for storing your strained oil, opt for one that is clean, dry, and airtight. Glass or plastic containers designed for high temperatures, such as HDPE plastic, are ideal. Avoid using metal containers, as they can react with the oil and cause it to become rancid faster.

Step 5: Store in a Cool, Dark Place

Light and heat are enemies of stored cooking oils. Once you have filled your container, seal it tightly and store it in a cool, dark place, such as a pantry or cupboard. Avoid storing the oil near sources of heat or direct sunlight, such as above the oven or fridge.

Tips for Reusing Stored Oil:

• Check its quality: Stored oil should be clear and free of any cloudy appearance, which indicates the presence of moisture that could lead to spoilage. It should also be odourless and flavourless.
• Don't mix oils: Avoid mixing different types of oils or fresh oil with used oil, as they have different smoke points and could degrade faster.
• Limit reuse: While reusing cooking oil is cost-effective and reduces waste, it should not be reused indefinitely. As a general rule, try not to reuse the same oil more than three times.

How often to change oil

How often you should change the oil in your deep fryer depends on several factors, including the type of oil, how often you use the fryer, and what foods you are frying.

Frequency of Use

If you are frying food in your deep fryer regularly, you should change the oil every one to two months. If you are frying food less often, you can wait up to two months to change the oil, even if it still looks and smells okay. Oil can turn rancid due to age or prolonged exposure to heat or light, so it's important to change it periodically to avoid spoilage.

Type of Food

The type of food you are frying also affects how often you should change the oil. If you are frying breaded foods, you should change the oil more frequently, as these foods tend to leave behind more particles that can burn and affect the oil's flavour. A good rule of thumb is to change the oil after three to four uses if you are mainly frying breaded foods. For battered foods, you can get away with about a dozen uses before changing the oil. For non-breaded meat or poultry, change the oil after three to four uses, and for vegetables, change it after six to eight uses.

Colour and Smell

Another way to tell if your oil needs to be changed is to pay attention to its colour and smell. If the oil looks cloudy or dark, or if it has foam on top and dark bits at the bottom, it's time for a change. Compare the colour to a fresh bottle of oil—if it's considerably darker, it's time for a replacement. Additionally, if the oil smells rancid or acrid instead of neutral, it's definitely time for a change.

Oil Maintenance

To extend the lifespan of your oil, it's important to maintain your deep fryer and store the oil properly. Always allow the oil to cool completely before pouring it into a container for storage. Use a cheesecloth to strain the oil and remove any food particles. Store the oil in a closed container in a cool, dry place, and consider refrigerating it to maximize its longevity.

Health risks of reusing oil

Reusing frying oil can be economical and environmentally friendly, but it's important to be aware of the potential health risks. Here are some detailed guidelines to help you understand the risks and manage them effectively:

• Harmful Compounds: When oil is heated, it breaks down and releases substances such as acrolein, which gives burnt food a bitter taste. Reusing oil that has surpassed its smoke point can lead to the formation of harmful compounds, giving food an acrid, greasy taste.
• Free-Radicals: If oil is not used, cooled, or stored properly, it can develop harmful free-radicals. These are atoms that have been linked to an increased risk of cancer and heart disease. This typically occurs when the oil is exposed to excess oxygen during the frying process, causing bubbles and leading to rancidity.
• Bacteria and Foodborne Illness: Deep frying, when done properly, can destroy bacteria. However, if food is not cooked to a safe minimum internal temperature, it can cause foodborne illnesses. Reusing oil that has not been filtered and stored correctly may increase the risk of bacterial growth.
• Allergens: Reused oil can pick up and transfer allergens from previously fried foods. This can be dangerous for individuals with food allergies.
• Degraded Oil Quality: Each time oil is reused, it becomes more destabilized until it decomposes. Reusing oil too many times can lead to a thick, gummy consistency and a darker colour, affecting the taste and texture of your food.
• Contaminants: Reusing oil that has come into contact with water or other contaminants can be dangerous. Water, for example, vaporizes instantly when it encounters very hot oil, causing oil to splatter and potentially burn your skin.
• Flavour Transfer: Oil tends to absorb the flavour of the food being fried. Reusing oil without proper filtering can result in flavour transfer, affecting the taste of your dishes.

Tips for Safe Oil Reuse:

• Always allow the oil to cool completely before handling or storing it.
• Filter and strain the oil after each use to remove food particles, which can burn and affect the taste.
• Store the oil in a sealed, light-proof container in a cool, dry place.
• Reuse frying oil no more than three times before discarding it.
• Do not reuse oil that has been stored for more than 1-2 months.
• Fry similar items in previously used oil to avoid flavour clashes.
• Do not pour oil down the drain as it can cause plumbing issues. Instead, dispose of it in a sealed container and throw it away with your regular trash.

By following these guidelines, you can minimize the potential health risks associated with reusing frying oil and enjoy your favourite fried foods safely.

How to dispose of oil

Disposing of oil is an important task that should not be overlooked. Improper disposal of oil can lead to clogged pipes and drains, water pollution, soil contamination, fire risks, and the spread of diseases. Here are some safe and eco-friendly ways to dispose of oil:

• The Container Method: Allow the oil to cool completely, then pour it into a sealable disposable container such as an old bottle or milk carton. Seal the container shut and throw it into the trash.
• The Freezer Method: Pour the oil into an old can and place it in the freezer until it hardens. Once solid, scoop the oil into the trash.
• The Plastic Bag Method: Pour cooled oil into a plastic trash bag that already has some absorbent debris like old paper towels or veggie peels. This helps to soak up the grease and minimise mess.
• Recycling: Check with your local waste department or websites like Earth911.com to see if there are any recycling sites that accept used oil. Sometimes, the oil can be used to make biodiesel fuel.
• Restaurants: If you live near a restaurant, you can give them your used oil for proper disposal. Some restaurants may even pay for it!
• Hazardous Waste Disposal Companies: Contact a household hazardous waste disposal company, as they often collect used cooking oil.
• Grease Disposal System: Install a grease trap, a plumbing device designed to intercept and retain fats, oils, and grease before they enter the wastewater system.
• Compost: Used cooking oil can be added to your compost pile in small amounts. It acts as food for earthworms, but too much can hinder airflow and suffocate microorganisms.
• Mix with Solid Waste Materials: Use absorbent materials like paper towels or sawdust to soak up and blot the oil. This converts it into solid waste, which is easier to handle.
• Burying: For small amounts of oil, you can bury it in your backyard. The oil will be broken down by bacteria in the soil. However, this method should be avoided if you have a sewage system as it can cause clogs.
• Reuse: Used oil can be reused a couple of times for frying similar items. Store it in a cool, dry, and dark place between uses, and be sure to strain it to remove any food particles.

Frequently asked questions