Mixing Frying Oils: What You Need To Know

Frying oils are a key component of any fried dish, but can you mix them? In short, yes, you can mix frying oils, but it's not recommended. When mixing two oils with different smoke points, the lower smoke point oil will start to degrade and burn at a lower temperature. This means that heating the mixture past the smoke point of the lower oil will result in wasting both oils. Additionally, oil degrades after prolonged oxidation or multiple heating cycles, so it's important to consider the number of times the oil has been used.

The smoke point of mixed oils

When mixing two oils, the smoke point of the mixture is limited by the lower smoke point of the two oils. For example, if you mix extra virgin olive oil with peanut oil, the extra virgin olive oil will start to degrade and burn at a lower temperature than the peanut oil. Heating the mixture past the smoke point of the lower oil means that both oils will be wasted.

Oil also degrades following prolonged oxidation (a few days) or multiple heating cycles. As little as eight heating cycles, which can be done in an hour or less in a commercial kitchen, can reduce the flashpoint of oil by more than 60 degrees Celsius.

Reusing frying oil

Firstly, it is crucial to start with the right type of oil. Oils with a high smoking point (400°F and above) such as peanut oil, canola oil, or vegetable oil are best suited for deep-frying. Extra-virgin olive oil, on the other hand, has a low smoke point, a dominant flavour, and is expensive, making it unsuitable for this purpose.

Temperature control is essential to prolonging the life of frying oil. When oil surpasses its smoke point, its fats start to break down and release acrolein, which gives food a bitter taste. Therefore, it is important to monitor the oil's temperature while heating and adjust the stove's heat as needed to maintain the desired frying temperature.

After frying, allow the oil to cool completely before straining it to remove any crumbs or sediment. This step is crucial if you are frying breaded or battered food as these particles will burn the next time you heat the oil. Straining can be done using a cheesecloth set in a fine-mesh strainer or coffee filters. Once strained, store the oil in an airtight container in the refrigerator.

It is important to note that frying oil takes on the flavour of the food cooked in it. Therefore, it is not advisable to use the same oil for frying fish and then doughnuts, for example. Labelling the oil with the date, the type of food it was used for, and the number of times it has been used is a helpful practice.

Frying oil can typically be reused anywhere from two to eight times, depending on the type of oil, what is being fried, and how well it has been strained. However, it is important to pay attention to any changes in the oil. If it becomes dark or dirty, smokes before reaching frying temperature, foams at the top, or develops a rancid or musty smell, it is time to discard it.

In terms of disposal, it is important to never pour oil down the sink drain as it can congeal and clog pipes. Instead, solidify the oil using a product like FryAway and then throw it away, or pour it into a sealable disposable container and dispose of it with the trash. Alternatively, depending on your location, you may be able to recycle used oil at a local disposal centre.

Filtering and storing used oil

Frying oil can be reused several times, reducing waste and cost. Once you're done frying, let the oil cool to 150-170 °F (65-75 °C) or to room temperature. Scoop out any large chunks of food from the oil. Then, strain the oil using a coffee filter, cheesecloth, or flour sack towel, placed in a sieve or jar. Slowly pour the oil into the filter, stopping when you reach the debris at the bottom of the frying pot. After filtering, pour the oil into a container with a tight-fitting lid and store it in a cool, dark place. Label the container with the date, the type of oil, and the number of times it has been used.

Oil will break down over time and should be discarded when it becomes dark or cloudy, develops a musty smell, emits smoke at frying temperature, or forms a layer of foam on its surface. Properly stored vegetable oil will last for 6-12 months.

How to dispose of frying oil

It is important to dispose of frying oil properly. You should never pour oil or grease of any kind down the drain, as it will solidify and stick to the inside walls of your kitchen pipes, eventually clogging them up. This same principle applies to all plumbing, so do not put oil in the toilet or a septic system.

The Container Method

Pour cooled oil into a disposable container (such as an old food container) and seal it shut. Then, throw the container away in the trash.

The Freezer Method

Pour oil into an old can and place it in the freezer until the oil hardens. Once it is firm, scoop the oil out and put it in the trash. If using smaller amounts of oil, allow it to harden in a disposable container, like a coffee mug, and then wash the mug as usual.

The Plastic Bag Method

Pour cooled oil into a plastic trash bag, preferably one that already has some absorbent debris inside, like old paper towels or veggie peels. These items will help soak up the grease so that you don't have as much of a mess.

Put It In The Trash

After the oil has cooled, use a funnel to pour it into a metal can or plastic container (e.g. an empty milk carton or the original oil bottle). Secure the lid and put the container in the trash. Make sure the oil is at room temperature before pouring it into a plastic container, as the heat from the oil will melt the container. Also, hot oil can attract bugs and animals to your trash.

Use Absorbent Materials

Mix the oil with absorbent materials like sand, flour, or cat litter to create a new "solid waste". These items will soak up the liquid.

Use A Recycling Centre

Some communities and businesses recycle cooking oil, sending it to refineries to be turned into biodiesel. Check with your local recycling centre to see if they accept used cooking oil. If so, use an empty gallon milk jug to collect the oil and, once full, recycle it. In some areas, you can contact local restaurants for assistance in disposing of cooking oil. You can transport your cooking oil to a restaurant equipped to handle the disposal or find a hazardous waste centre that allows drop-offs.

Best oils for deep frying

Deep frying requires high temperatures, often over 400 degrees Fahrenheit. When choosing an oil for deep frying, any refined oil will work. Refined oils have higher smoke points, which means they can handle the higher temperatures used in deep frying. The thermal stress caused by the higher temperatures can easily deteriorate and oxidize less stable oils, so it's important to use a sturdier option.

The Best Oils for Deep Frying

The refined oils that are most commonly used for deep frying include safflower and soybean oil, the latter of which is often labelled as vegetable oil. Vegetable oil is a blend of different plant-derived oils, such as corn oil, soybean oil, and sunflower oil, blended together for maximum cost-effectiveness.

Other good options include:

• Peanut oil
• Canola oil
• Sunflower oil
• Corn oil
• Rice bran oil
• Avocado oil
• Light or refined olive oil

These oils are all high-heat oils, with smoke points between 400° and 450°. When deep frying, you'll often aim to reach a temperature of around 350°, so these oils are not likely to get anywhere near smoking.

Oils to Avoid

Oils with lower smoke points are best avoided when deep frying, as they will rapidly burn and degrade at high heat, ultimately losing their flavour. Examples include flax seed, walnut, hazelnut, almond, and extra-virgin olive oils. These oils are best used in raw preparations, such as dressings or drizzled on finished dishes.

Frequently asked questions