Why Cooking Oil With Low Smoke Point Is Suitable For Frying And Cooking
What is the stability quality index of edible oil after heating? Oxygen, moisture (naturally present in food) and high temperature make oils prone to hydrolysis, oxidation and polymerization (polymerization), these chemical reactions affect the chemical structure of oils, produce free fatty acids and free radicals, and then produce monoacylglycerols , diacylglycerol and other harmful variations, these substances are collectively referred to as polar compounds (polar compounds) or TPM (total polar material). Animal experiments have proved that TPM is the most toxic one under the oxidation indicators of various oils (Pantzaris T.1998), and must be strictly controlled.
In addition to TPM, polymerized triacylglycerols (PTG) are also harmful to humans. The higher the temperature, the longer the heating time, and the more times it is used, the higher the ratio of TPM and PTG in the oil. TPM and PTG affect health, so the amount of TPM and PTG are the two most important indicators to measure the degree of oil deterioration. Many countries in Europe, the United States and Japan have regulations on the ratio of TPM and PTG in industrial edible oils (but only some countries make mandatory regulations). The TPM index generally does not exceed 25%, and the PTG index generally does not exceed 15%. More stringent (10% of Belgian PTG indicators), beyond these safety indicators, the oil can no longer be used. In addition to the above two indicators, the proportion of free fatty acids, the degree of degradation of antioxidants in oil at high temperature, the value of trans fat produced at high temperature, etc., are all important indicators to measure the performance of edible oil at high temperature.
In 2018, the Australian Modern Olive Laboratory published the results of a study on edible oil experiments, which also confirmed that the smoke point has no relationship with the stability of the oil after heating.
In the experiment, a variety of edible oils were heated from 25 degrees Celsius to 240 degrees Celsius to simulate the environment of cooking, and different edible oils were kept at 180 degrees Celsius for 6 hours to simulate the environment of slow cooking, and then the composition of the oil was analyzed to determine the safety of the oil and stability. Studies have shown that the smoke point is not indicative of the safety and stability of an oil. The smoke point is closely related to the carbon chain length of fatty acids. Fatty acids with longer carbon chains have higher smoke points, but this does not mean that oils with high smoke points are safer and more stable after heating. Experiments have shown that olive oil is the most stable and safest when heated (virgin olive oil is better than refined olive oil), produces the least polar compounds (prone to inflammation in the body) and the least trans fat after heating, followed by coconut oil And avocado oil, although the most common olive oil is more stable than other vegetable oils, other commonly used vegetable oils produce relatively high levels of harmful substances, among which canola oil performed the worst in the experiment, and the harmful substances produced after heating are olive oil more than double that. Olive oil also retains more antioxidants when heated than other vegetable oils.
In 2012, an experiment conducted by a Bulgarian scholar (Marinova 2012) compared the time required for the toxic substance TPM to exceed 25% after heating various edible oils. As mentioned above, most countries require that the TPM index of edible oil used in industry and commerce should not exceed 25%. It can be seen from the table below that the time when the harmful substance TPM exceeds the standard has nothing to do with the smoke point. The scholars of the study mentioned that the stability of the oil is mainly related to the antioxidant nutrients in the oil, such as vitamin E and polyphenols. The more antioxidant micronutrients, the longer the heating time to keep the TPM index at a safe ratio .
Another study published in the academic journal "Food and Chemical Toxicity" in 2010 (Casel et al 2010) also confirmed that the oxidative and hydrolytic stability of virgin olive oil after heating is very high. Clearly tolerated: "olive oil is clearly resistant to frying conditions".
Similarly, an experiment with sunflower oil and olive oil (S. Bastida 2001) also demonstrated that olive oil was more stable than sunflower oil in terms of resistance to oxidation or hydrolysis under repeated heat use.
A study (Yosra Allouche et al) published in 2007 showed that despite the extreme heating of olive oil (180 degrees Celsius for 36 hours), vitamin E and some antioxidants in olive oil have been greatly affected. damage, but other important nutrients in olive oil are still intact, and the conclusion is also that olive oil has a high antioxidant stability after heating.
Another study (Andrikopoulos et al 2002), using olive oil for frying and frying potatoes (similar to McDonald's French fries, a pot of oil recycling) after 10 cycles, the polar compounds in the oil were 9.5% and 17.5%, which is still lower than the safety standard 25% stipulated by most countries, and it is better than other commonly used vegetable oils.
If the above research is not enough, I was stunned by the following newer research in 2018. Some scholars studied the waste water left over from the production of olive oil and extracted it as an antioxidant in sunflower oil (and other vegetable oils), saying that The remaining antioxidants in these wastewaters are sufficient to enhance the stability of sunflower oil at high temperatures. Why would I use sunflower and other vegetable oils instead of olive oil for cooking, if that's all I can do? But this study shows that antioxidants, rather than smoke point, are more important for the stability and safety of cooking oils.
In fact, the polyunsaturated fatty acid contained in most plants is omega 6 (omega-6). Although omega-6 and omega-3 are also essential fatty acids for the human body, the daily diet is generally too much omega-6 and too little The omega-3 in the body makes the body prone to inflammation, and it is especially easy to oxidize the low-density cholesterol apolipoprotein (LDL) in the blood vessels, thereby causing cardiovascular diseases. However, omega-3 oils such as flaxseed oil and fish oil are extremely easy to oxidize and must not be heated, so if you need to use cooking oil while maintaining health, the only way is to reduce the use of omega-6 oils, including basically All most vegetable cooking oils (e.g. corn oil, soybean oil, sunflower oil, etc.) except coconut oil, avocado oil, olive oil. But no matter from the perspective of heat stability to reduce carcinogenic toxins or reducing the intake of omega-6 fatty acids to reduce the risk of cardiovascular disease, I suggest that the use of various vegetable oils commonly used today should be reduced. Although the smoke point of olive oil is often misunderstood as cooking oil not suitable for heating, many research reports have proved that the smoke point is misleading. I hope that everyone can choose cooking oil more rationally in the future.
