Deep Fryer Oil: When To Change It And Why

How often you should change the oil in a deep fryer depends on a variety of factors, including the type of oil, the food being fried, the frequency of oil filtration, and the temperature at which the oil is heated. For example, oils with high smoke points like canola, sunflower, and vegetable oils are better suited for high-temperature deep frying and can be reused more often. On the other hand, oils with low smoke points can become rancid after just one or two uses.

The frequency of oil changes also depends on the volume of food being cooked and the type of establishment. A busy fast-food restaurant may need to change their oil every week or two, while a lower-volume kitchen can go two to three weeks between changes.

It's important to change the oil regularly to maintain the taste of fried foods and to protect your health. Reusing oil for too long can lead to increased cholesterol, acidity, and inflammation levels, as well as expose you to various health risks. Some signs that your oil needs to be changed include a burnt or stale taste in the food, a darker colour and thicker consistency, and an unusual amount of smoke.

Oil type and smoke point

The type of oil used for deep frying is important for both flavour and health. The smoke point of an oil is the temperature at which it starts to smoke, which is before its boiling point. Heating an oil past its smoke point can result in the formation of carcinogens and a burnt taste.

Factors Affecting Smoke Point

Each oil has a different smoke point, depending on the following factors:

• Refining — Refined oils have a higher smoke point because the refining process removes impurities and free fatty acids that cause oils to smoke.
• Type of fat — Oils high in polyunsaturated fats, such as sunflower, flaxseed, or safflower, have lower smoke points. Oils higher in monounsaturated fats, such as avocado, canola, and olive, have medium smoke points. Oils high in saturated fats, such as coconut and palm, have high smoke points.
• Age — As an oil ages, exposure to light, heat, and air can lower its smoke point.

High Smoke Point Oils

A high smoke point is 400 degrees F and above. Oils with high smoke points are best for frying. Examples include:

• Avocado oil
• Canola oil
• Corn oil
• Peanut oil
• Safflower oil
• Sunflower oil
• Vegetable oil

Low Smoke Point Oils

A low smoke point is 225 degrees F or less. Oils with low smoke points should not be heated and are best used for salad dressings or garnishes. Examples include:

• Flaxseed oil
• Pumpkin seed oil
• Walnut oil

Other Considerations

• Smoke point range — Smoke points can vary depending on the quality of the oil, the type of heat used, the amount of air in the oil container, and the free fatty acid content.
• Oil freshness — The longer an oil is exposed to heat, the lower its smoke point becomes. Therefore, fresher oil tends to have a higher smoke point than oil that has been used for a while.
• Oil usage — When deep-frying, bits of batter or breading will drop into the oil, accelerating its breakdown and lowering its smoke point.
• Health — All cooking oils that are liquid at room temperature are generally considered healthy. However, oils with higher levels of polyunsaturated fats are considered healthier as they increase HDL ("good" cholesterol) and lower LDL ("bad" cholesterol). Oils with lower levels of saturated fats are also considered healthier.

Frequency of use

The frequency with which you should change the oil in a deep fryer depends on several factors, including the type of oil, the food being fried, the frequency of oil filtration, and the temperature at which the oil is heated.

In a high-volume fast-food restaurant, it may be necessary to change the oil every week or two. However, this can vary based on the size of the vats and the quality of the filters. In establishments where fryers are constantly in use, the filter should be changed daily.

For french fries and other non-breaded food items, it is recommended to change the oil after 6 to 8 uses. For breaded, poultry, meat, and crumbly foods, the oil should be changed after 2 to 4 uses as these foods tend to leave more residue and crumbs that can burn and cause the oil to go rancid. For breaded fish, the oil should be changed after 2 to 3 uses.

It is important to note that reusing deep-frying oil for too long can have negative health effects, such as increased inflammation, cholesterol, and acidity levels. Additionally, oil that is heated at high temperatures can become rancid, develop a burnt taste, and release toxic elements called aldehydes.

To prolong the life of your deep-frying oil, it is recommended to strain or filter the oil after each use, store it in a sealed container, and avoid cooking at extremely high temperatures.

Food fried

Frying food is a delicate process that requires attention to detail to ensure the best results. One of the most important considerations when frying is the quality of the oil used. While it may be tempting to reuse oil to save time and money, doing so can negatively impact the taste of your food and even pose health risks. Here are some guidelines to help you maintain the quality of your fried food and protect your health:

Choosing the Right Oil

The type of oil you use is crucial. Oils with high smoke points, such as canola, sunflower, peanut, avocado, and vegetable oils, are ideal for deep frying as they can withstand high temperatures without burning. Oils with low smoke points will not only affect the flavour of your food but will also turn rancid after just a few uses.

Frequency of Oil Changes

The frequency with which you should change your deep fryer oil depends on several factors, including the type of food being fried, the frequency of oil filtration, the oil type, and the temperature at which the oil is heated. For example, breaded foods like chicken or fish will require more frequent oil changes (every 2 to 4 uses) compared to non-breaded foods like French fries or vegetables (every 6 to 8 uses). It's important to monitor the colour and consistency of the oil, as oil that has gone rancid will become darker and thicker.

Health Risks of Reusing Oil

Reusing deep-frying oil for too long can have negative health consequences. Reheated oil can increase inflammation, cholesterol, and acidity levels in the body. Consuming rancid oil can also lead to a higher risk of developing heart disease and other infections due to the presence of toxic elements called aldehydes.

Prolonging Oil Life

To make the most of your oil and reduce unnecessary expenses, you can follow these simple steps:

• Always strain or filter the oil after use to remove excess batter and impurities.
• Store the oil in a sealed container to prevent contamination from outside particles.
• Monitor the temperature of the oil with a thermometer to avoid overheating, which can make the oil rancid.
• Avoid adding salt to your food before frying, as salt particles can negatively affect the quality of the oil.
• Store unopened oil in a cool, dark place, and refrigerate stored oil to maximise longevity.

In conclusion, paying attention to the quality of your deep-frying oil is essential for both taste and health reasons. By choosing the right oil, changing it frequently, and following proper storage and filtration practices, you can ensure your fried food is delicious and safe to eat.

Oil storage

• Container Type: Use a designated oil storage container made from stainless steel or another suitable material. Containers with a removable strainer or fine-mesh sieve are ideal for catching fine particles and preventing contamination. Look for containers with a snug lid to prevent spills and dust or particle intrusion.
• Cooling and Straining: Before storing, allow the oil to cool completely. Oil burns can be dangerous and painful. Once cooled, strain the oil through a cheesecloth or fine-mesh sieve to remove any food particles or debris.
• Storage Location: Store the container in a cool, dry, and dark place, away from heat sources such as ovens or appliances. Avoid placing it near the fridge or microwave, as these areas can get warm.
• Storage Temperature: If possible, store the oil in a refrigerator to maximise its longevity. This is especially important for oils with a high smoke point, such as canola, sunflower, peanut, and avocado oil.
• Container Size: Choose a container size that accommodates the amount of oil you typically use. Containers come in various sizes, from 1-gallon to 10-gallon capacities.
• Labelling: Label the container with the date and type of oil for easy reference. This helps you keep track of how long the oil has been stored and ensures you use the oldest oil first.
• Shelf Life: Even when stored properly, deep fryer oil has a limited shelf life. Once opened, oil should be used within three months. Additionally, oil that has been used for frying should be filtered and stored in a closed container, but it will not last as long as fresh oil.
• Disposal: Do not pour used oil down the drain, as it can cause pipe blockages and environmental issues. Instead, dispose of it responsibly by using a designated oil disposal caddy or recycling it through a reputable company. Some companies will pay you for your used fryer oil.

Oil lifespan

The lifespan of oil in a deep fryer depends on several factors, including the type of oil, the food being fried, the frequency of oil filtration, and the temperature at which the oil is heated.

Type of Oil

Oils with a high smoke point, such as canola, sunflower, peanut, avocado, and vegetable oils, are better suited for deep frying as they can withstand higher temperatures without smoking or becoming rancid. Oils with lower smoke points may become rancid after just one or two uses.

Frequency of Use and Filtration

The more frequently the oil is used, the sooner it will need to be changed. Filtering the oil after each use can help extend its lifespan by removing excess batter and impurities. In high-volume fast-food restaurants, oil may need to be changed as often as every week or two, while in lower-volume kitchens, oil can last for up to two weeks or even a month.

Food Being Fried

The type of food being fried also impacts the lifespan of the oil. Breaded and crumbly foods, such as fried chicken and fish, can cause the oil to go rancid more quickly due to the higher temperatures required to fry the batter. For these types of foods, the oil should be changed after two to four uses. For non-breaded foods, such as French fries and vegetables, the oil can be reused for six to eight uses before needing to be changed.

Temperature

Oil should be heated to a high enough temperature to achieve the desired crispiness of the food, but overheating the oil can cause it to degrade more quickly. Oil heated at extremely high temperatures can become rancid, darken in colour, and thicken in consistency.

Signs of Oil Spoilage

It is important to regularly monitor the quality of the oil to ensure it has not gone bad. Oil that has turned rancid will have an unpleasant taste and smell, become darker in colour, and may produce more smoke than usual. Cooking with rancid oil can negatively impact the taste of food and pose health risks to those consuming it.

Extending Oil Lifespan

To maximise the lifespan of the oil, it is recommended to keep the deep fryer clean, store unopened oil in a cool and dark place, filter and store used oil in a closed container, avoid cooking at temperatures above 375 degrees Fahrenheit, and add salt to foods only after deep frying.

Frequently asked questions