Whether the edible oil is resistant to high temperature is first related to saturation. The higher the saturation is, the more stable the temperature is. The higher the degree of unsaturation is, the easier it is to oxidize rancidity.
The fatty acids contained in oils can be classified according to their saturation.
Saturated fatty acids, such as palmitic acid, stearic acid, palm oil, coconut oil, animal oil
Monounsaturated fatty acids: oleic acid, Omega -9, such as olive oil, camellia seed oil and rapeseed oil.
Two unsaturated fatty acids: linoleic acid, Omega -6, such as sunflower seed oil, corn oil, soybean oil.
Polyunsaturated fatty acids: alpha linolenic acid, HDA, EPA and so on, Omega -3, such as flaxseed oil and fish oil.
Olive oil is rich in oleic acid (75%). It belongs to the oil with high saturation. It only shows from fatty acid composition that it has high heat resistance.
The content of oleic acid in mustard seed oil and peanut oil is quite high, which is 61% and 48% respectively, and the content of alpha linolenic acid in mustard seed oil is 11%, which is more beneficial to health.
Secondly, it is related to the processing degree of edible oil. The higher the content of the impurities in the edible oil, the more easily the oxidation of the acid, so the edible oil sold in the market is stable for quality. In the process of processing, it has passed "six" - dehydration, degumming, decolorization, deodorization, dephosphorization and deacidification. The water, impurities, pigments, odors, phospholipids, free fatty acids, etc. affect the stability and bad flavor of the oil. When the substance is removed and added antioxidants, the edible period of edible oil at normal temperature can reach 18 months. After the "six" oil, the smoke point is greatly improved, mostly from 100 degrees centigrade to 200 degrees centigrade, stir fry "hot pot cold oil", low oil smoke, good effect of the dishes.
Why can't the olive oil be heated?
More than 70% of the fatty acids of olive oil are oleic acid. Oleic acid has no special physiological regulation function besides energy, organization and heat preservation. The reason why olive oil is respected is that the olive oil is rich in polyphenols, vitamin E and other antioxidants. It is considered to have health benefits.
However, in order to keep these substances in the oil, the extraction process of olive oil is like the propaganda, using cold press, that is, low temperature physical press, and the most highly praised is "special primary press", that is to say, without "refining", all kinds of "Za" (Zhi) are kept in the oil.
The smoking point of this kind of oil is very low. When heated, the oil smoke is very large, and it is easy to destroy the so-called beneficial substances. In addition, as the impurities in the virgin olive oil have the astringency of polyphenols and the peculiar smell of Olives, the smell is more intense in the stir fry, which will destroy the aroma of the food.