The word "salad oil" originates from the West, as the name implies, salad oil, and salads, Westerners use raw vegetables as their main ingredient, supplemented with a variety of seasoning salad dishes, in order to increase nutrition, they need to be painted on top. Oily coating, this is salad oil. In order to maintain the inherent color and taste of vegetables, this oil needs to be colorless and odorless. Since cold dishes are often required to be refrigerated, they cannot be condensed at low temperatures, and the transparent liquid state must be maintained at 4.4°C. Therefore, the salad oil needs to remove the non-triglyceride components in the vegetable oil as much as possible, generally only vegetable oil.
Cooking oil, also called cooking oil, cooking oil, can be vegetable oil or animal oil (here refers to vegetable oil). Cooking oil should be liquid at room temperature, good fluidity, rich in oil's inherent nutrients, and no annoying odor. Strictly speaking, it is different from frying oil. The most important feature of frying oil is that long-term high temperature (160°C-180°C) is not easily deteriorated, ie, thermal oxidation and hydrolysis do not occur.
In Europe and the United States, cooking oil and frying oil are all within the shortening range of different physical properties, while salad oil is specifically referred to as liquid cold oil. In Japan, cooking oil, cold oil (salad oil), and frying oil are highly specialized and their characteristics differ greatly.
China's current edible oil according to national standards, such as the consumption of a primary oil, secondary oil, senior cooking oil, salad oil and so on. As far as the consumption level in most regions is concerned, cooking oil has not yet distinguished cooking oil and cold oil (salad oil). In most regions, eating habits are mainly used for cooking, that is, for cooking, and therefore mainly cooking oil. . In recent years, with the introduction of oil refinery production lines and the continuous maturation of domestic refining equipment, the production of salad oil and refined oils of various corporate standards has been continuously improved, together with the advertising effect of some manufacturers, some cities and regions have gradually consumed edible oil. Turning to refined oils such as salad oil, this shows that people's consumption levels have increased and they are pursuing more refined and purer foods. However, from a nutritional point of view, using salad oil as a cooking oil is not appropriate and worth exploring.
From a chemical point of view, most of the existing natural oils and fats are composed of fatty acid triglycerides (glycerides) with different degrees of saturation and unsaturation and are accompanied by a small amount of lipid substances. These lipids mainly include phospholipids, free fatty acids, sterols and sterol esters, vitamins, pigments, terpenes, waxes, fatty alcohols, hydrocarbons, etc. Most of them are harmless to the human body, but there are still some ingredients and some oils. The oil contains toxic ingredients that must be removed. From crude oil to salad oil, it is generally required to undergo degumming (dephosphorization), deacidification, decolorization, deodorization, and some oil products need to be processed by dewaxing and other processes. After these refining processes, there will be a series of changes in the main lipid components of the oil and the nutrient content of the oil.
Phospholipids
The content of phospholipids in crude vegetable oil varies depending on the type of oil and the preparation method, and is generally 0.1% to 3%. Soybean oil has a high phospholipid content of about 1%-3%.
Phospholipids have the ability to mediate metabolism, enhance physical fitness, strengthen brain, supplement brain, eliminate brain fatigue, enhance intelligence, improve human memory, reduce human blood cholesterol, regulate blood lipids, prevent atherosclerosis, protect the human liver, prevent fatty liver, Prevention of gallstones, prevention of osteoporosis in the elderly, prevention of Keshan disease and other functions, and has an antioxidant effect on oil, but in oil refining has to bear the brunt of the removal of the main reasons are: (1) mixed with oil The color of the oil is dark and turbid; (2) The oil contains water or is stored for a long time, and the phospholipids absorb water, precipitate, and accelerate the deterioration of the oil; (3) Heated to 280°C and begins to burn harder and darker; (4) Phospholipids, etc. The existence of quality directly affects the completion of subsequent processing steps such as deacidification, decolorization and deodorization.
As a general cooking oil, dephosphorization is necessary from the viewpoint of storage and high-temperature cooking in most regions.
The main process for removing phospholipids is degumming, which removes 76% of the phospholipids in the hair oil and removes it almost 100% after deodorization.
Second, free fatty acids (FFA)
Fats and oils contain free fatty acids, mainly due to fatty acids that have not been synthesized as esters in the raw oil. Oils can also produce FFA due to moisture, heat from digested lipase, or oxidative decomposition during storage. Generally about 0.5% to 5% of the unrefined vegetable oils and fats, FFA can be as high as 20% or more in rice bran oil and palm oil which are decomposed by lipase.
The main purpose of deacidification of fats and oils should be reflected in: the high content of FFA has a greater impact on the tastes of the consumers and the flavor of the dishes, and does not have any harm to the human body itself.
Third, the pigment
The pigments in oils and fats are mainly natural pigments, including carotenoids and chlorophylls. The most abundant carotenoids in nature are beta-carotene, followed by alpha-carotene, and very few gamma-carotene. Beta-carotene is oxidized by carotenease in the liver, and the carbon chain is broken into alcohol, which is two molecules of vitamin A1. Therefore, carotene is a source of vitamin A and has physiological value. Moreover, carotene absorbs light energy and acts as an antioxidant. In the absence of light, because of its high degree of unsaturation, it is easier to oxidize than oil, thus protecting the oil. At the same time, studies have shown that it also has the effect of inhibiting cancer cell proliferation and improving immunity. Therefore, carotene combines the dual functions of coloration and nutritional supplementation. Because the natural pigment in fats and oils is mainly carotene, unless it is a light-colored special oil used for special purposes, such as salad oil, margarine, light-colored paint, cosmetics, etc., as a cooking oil, there is no need to decolorize.
Four, sterols
The sterols in animal fats and oils are mainly cholesterol, and the sterols in vegetable oils are mixtures of various sterols, such as stigmasterol, β-sitosterol, ergosterol, and the like. The content of sterols in fats and oils varies depending on the oil product. The contents of wheat germ oil (1.30%-1.70%), corn germ oil (0.58%-1.0%), and rice bran oil (0.75%) were higher. Plant oil, refined, especially