As the weather gets colder, people who cook often will find that their cooking oil at home has partially solidified into a white, waxy substance, while some remains golden and transparent. Does the solidification of crude oil mean the oil is impure?
Is it because the oil is mixed with lard or other components of "gutter oil" that it solidifies into a white solid? Can this be used to identify "gutter oil"?
In fact, whether peanut oil solidifies is only one of the criteria for judging the quality of the oil. Different oils have different freezing points. Palm oil and coconut oil have the highest freezing points, around 20°C—30°C. Peanut oil solidifies at 4°C. The freezing points of soybean oil, corn oil, and canola oil are below 0°C. Animal fats have a higher freezing point and are usually solid at room temperature.
However, this is not a fixed value, just as most brands of peanut oil do not specify on their labels at what temperature they will solidify. Based on my personal observation, peanut oil can sometimes solidify at 6°C—8°C. Therefore, relying solely on the solidification phenomenon to determine the purity of cooking oil is not a reliable method.
The freezing point of cooking oil is closely related to the content and ratio of saturated and unsaturated fats in the oil. During the refining process, the more thoroughly the fat is removed, the lower the oil's solidification point, and the less likely it is to solidify as the temperature drops. Broadly speaking at room temperature, vegetable oils (except palm oil) do not solidify, while animal fats, which are high in saturated fat, do. It cannot be simply said that oil that can solidify is good oil.
In the past, people's understanding of the concepts of "oil" and "fat" in cooking oil was not high, and coupled with backward oil refining technology, it made some sense to simply judge the raw material of the oil based on the solidification phenomenon when cooled.
Today, with advancements in oil refining technology, cooking oils with different ratios of saturated and unsaturated fats can also be produced, which determines their different freezing points.
So, faced with the various cooking oils on the market today, how should we choose and use them?
In terms of the source of cooking oil, there are mainly animal and vegetable fats. In daily life, try to use less animal fat. On the basis of controlling the total amount, choose vegetable oil. In the absence of sufficient evidence to prove that genetically modified (GM) foods are harmless, it is recommended to choose non-GM vegetable oils.
In terms of processing technology, prioritize oils produced by physical pressing methods and use less oil produced by chemical extraction methods, as they may contain some harmful residues from the chemical processing process. Although they are within safe limits, it is better to minimize intake.
Different cooking oils, due to their different chemical properties and nutritional content, are also suitable for different cooking methods.
Butter: Suitable for frying food. Because it contains a large amount of saturated fat, its chemical properties are stable and it has a high smoke point, so it is less likely to produce oxygen free radicals that can harm the body at high temperatures. However, be mindful of controlling the intake to prevent excessive intake from harming the cardiovascular system.
Canola oil and soybean oil: Extremely versatile. Canola oil can be used for stir-frying, braising, roasting, and making salads.
If you want to enjoy the heart-healthy benefits of olive oil but find its flavor too strong, try mixing canola oil and extra virgin olive oil in a 1:1 ratio when making salad dressings.
When heating, pay attention to controlling the oil temperature, with the best practice being not to let it smoke, otherwise trans fatty acids will be produced.
Peanut oil: It has a high smoke point, making it suitable for deep-frying and grilling food. It also contains plant sterols that are beneficial for heart health, which can lower cholesterol and inhibit cancer cells.
Corn oil and sunflower oil: They contain less saturated fat and more unsaturated fat, especially polyunsaturated fat. However, the vast majority of it is omega-6 fatty acid, so excessive consumption is not recommended.
Sesame oil and olive oil are suitable for cold dishes and salads. Olive oil, in particular, contains more antioxidants, which have a protective effect on the cardiovascular and immune systems.