Old Deep Fryer Oil: Safe Or Sickness Inducer?

Deep-frying at home is a messy, costly, and dangerous affair. However, if you're using a lot of oil, you should get the most out of it. While you can reuse frying oil, there are some rules to follow. For instance, it's important to start with the right type of oil. Every oil has a specific smoking point, so for deep frying, it's best to use an oil with a high smoking point (400°+) like peanut, canola, or vegetable oil.

To prolong the life of your oil, temperature control is key. When oil surpasses its smoke point, its fats start to break down, releasing a substance called acrolein, which gives burnt food a bitter taste. Frying with old oil will cause food to taste acrid and greasy. If you want to reuse your fryer oil, monitor the temperature to ensure it doesn't surpass its smoke point. Once you've finished frying, allow the oil to cool completely before filtering it to remove any impurities.

Each time you reuse oil, it gets more and more destabilized until it decomposes. Reusing frying oil is safe from a bacterial growth standpoint, but it's important to look out for signs of spoilage. If the oil has a rancid smell or taste, or appears cloudy or foamy, it's time to toss it. Even if the oil looks and smells fine, it's recommended to reuse frying oil no more than three times before discarding it. Consuming rancid oil may not make you sick right away, but it can develop harmful free radicals that cause long-term cell damage and potentially lead to chronic diseases.

Rancid oil may not make you sick right away but can cause long-term cell damage

While consuming rancid oil may not make you sick right away, it can have negative health effects in the long run. Rancid oil can develop harmful free radicals that cause long-term cell damage and potentially lead to the development of chronic diseases.

Rancidity refers to the natural spoilage of oils and fats caused by changes in their chemical structure. Exposure to warm temperatures, oxygen, light, and some metal varieties are major factors in the progression of rancidity. Oils become rancid faster than solid fats, and vegetable-based oils can lose their optimum food quality after a relatively short period of time. For example, after one to three months of room-temperature storage, vegetable oils' quality noticeably degrades.

Consuming rancid oil can trigger digestive system distress and drain vitamins B and E from your body. Rancid oil can also form dangerous free radicals that contribute to cell damage and have been linked to the development of Alzheimer's disease, diabetes, and other diseases that manifest over time. In addition, free radicals have been shown to damage arteries and function as carcinogens.

Therefore, it is essential to properly store and dispose of frying oil to minimize potential health risks. Used frying oil should be strained and stored in a sealed container in a cool, dark place. It can be reused several times, but it is important to monitor it for any changes in colour, smell, or texture, which may indicate that it has gone rancid.

Oils with a high smoking point (400°+) are best for deep frying

Oils with a high smoking point are best for deep frying. The ideal deep-frying temperature is between 350°F and 375°F, so oils with a smoke point above 375°F are preferable.

Oils with a high smoke point include peanut oil, canola oil, vegetable oil, corn oil, soybean oil, avocado oil, and sunflower oil. These oils have smoke points ranging from 400°F to 570°F.

Using an oil with a high smoke point is important because when oil surpasses its smoke point, its fats start to break down, releasing a substance called acrolein, which gives food a bitter taste. Additionally, heating oil past its smoke point could start a fire.

It's also important to note that the smoke point of an oil is not constant and can decrease over time. The longer an oil is exposed to heat, the lower its smoke point becomes. Therefore, it's recommended to use oils with smoke points of at least 400°F for deep frying.

When choosing an oil for deep frying, other factors to consider include cost, health benefits, and flavour. For example, avocado oil has a high smoke point but is more expensive, while canola oil is more affordable and has the added benefit of being neutral in flavour.

To prolong oil's life, control its temperature to avoid surpassing its smoke point

To prolong the life of your oil, it's important to control its temperature to avoid surpassing its smoke point. Every oil has a specific smoke point, or the temperature at which it starts to smoke. When oil surpasses its smoke point, its fats start to break down and release a substance called acrolein, which gives burnt food a bitter taste.

To avoid this, carefully maintain the oil's temperature as you fry by monitoring it with a thermometer and adjusting the heat as needed. By doing so, you can not only improve the taste of your food but also stretch the shelf life of your oil.

Additionally, using oils with a higher smoke point, such as peanut oil, canola oil, or vegetable oil, is recommended for deep frying, as it occurs at high heat. On the other hand, oils like extra-virgin olive oil, with its low smoke point, are not suitable for deep frying.

Other factors that can help prolong the life of your oil include using a deep fryer with a cold zone, which reduces particle build-up, and filtering the oil regularly to remove impurities and food particles.

Store oil in a cool, dark place

Storing oil in a cool, dark place is essential for preserving its quality and preventing spoilage. Here are some detailed instructions and tips for storing your oil correctly:

• Keep the oil in a cool location: Aim for a stable temperature between 50°F and 70°F (14°C and 21°C). Storing oil in a cool place slows down the oxidation process and prevents the formation of harmful free radicals.
• Avoid storing oil near heat sources: Do not keep oil near the stove, oven, or dishwasher. The heat emitted by these appliances can cause the oil to degrade and spoil faster.
• Choose the right container: Use a dark-coloured glass bottle, ceramic bottle, or stainless steel container. These materials block sunlight and small molecules, preventing oxidation and preserving the oil's beneficial compounds. Avoid clear glass bottles, plastic containers, and reactive metals like copper or iron.
• Keep the container sealed: Always replace the cap or lid on the oil container when not in use. Oil can turn rancid due to exposure to oxygen, so ensure the container is tightly sealed.
• Store oil away from sunlight: Place the oil in the darkest part of your kitchen, such as a cabinet with closing doors or a wine cellar. Sunlight can alter the properties of the oil, reducing its beneficial ingredients.
• Be mindful of temperature fluctuations: Avoid storing oil in areas with frequent temperature changes, such as near a window or above the stove. These fluctuations can cause the oil to deteriorate and turn rancid.
• Consider refrigeration: Refrigeration can extend the shelf life of certain oils. However, for expensive extra virgin olive oils, condensation may affect their flavour.
• Transfer oil to smaller containers: If you have a large bottle or tin, consider transferring some oil to a smaller, dark-coloured glass bottle. This makes it easier to manage and reduces waste if one container goes bad.
• Label and date your oil: Mark the type of oil and the date of purchase or opening. This helps you keep track of the oil's freshness and prevents using it beyond its recommended period.
• Use oil within its recommended timeframe: Oils have different shelf lives, so refer to storage guidelines for specific types of oil. In general, refined oils last 6 to 12 months, while unrefined oils last 3 to 6 months when stored properly.

Reuse oil within one to three months

Reusing deep fryer oil is an excellent way to reduce waste and cut costs. However, it is important to be mindful of the oil's lifespan and take the necessary steps to ensure it is safe for consumption. Here are some detailed instructions and guidelines to help you reuse oil within one to three months:

Storing and Straining the Oil

Once you have finished frying, allow the oil to cool completely in the frying vessel. This step is crucial, as attempting to filter hot oil can cause serious burns. After the oil has cooled, it's time to strain it to remove any loose crumbs or sediment. This process is especially important if you plan to fry breaded or battered foods, as these particles can burn the next time you heat the oil. Use a fine-mesh strainer or a cheesecloth set in a strainer, and pour the oil into a clean, airtight container, such as a glass jar or its original container.

Labelling and Storage

Before storing the strained oil, be sure to label the container with the date, the type of food it was used for (e.g., "doughnut frying oil"), and the number of times it has been used. This information will be helpful in determining when the oil needs to be discarded. Store the container in a cool, dark place, such as a cupboard or pantry, until you are ready to reuse it.

Reusing the Oil

Frying oil can typically be reused anywhere from two to eight times, depending on various factors such as the type of oil, the food being fried, and the effectiveness of the straining process. However, it is important to pay close attention to the oil and look for any signs of degradation. If the oil becomes dark or dirty, smokes before reaching frying temperature, foams at the top, or develops a rancid or musty odour, it is time to discard it. Additionally, be mindful that frying oil takes on the flavour of the food it was used to fry, so consider this when planning your next frying project. For example, oil used for frying fish may not be suitable for frying desserts.

Health Considerations

While reusing frying oil can be a great way to reduce waste, it is important to be mindful of potential health risks. Each time oil is reused, it becomes more destabilized until it eventually decomposes. Reusing oil multiple times can lead to the formation of harmful free radicals, which have been linked to long-term cell damage and the development of chronic diseases such as Alzheimer's and diabetes. Therefore, it is recommended to reuse frying oil no more than three times before discarding it and to avoid reusing oil that has been stored for more than one to three months.

Frequently asked questions