True points:
"Leaching oil" is one of the processes used to make edible oil, and the allegations of its safety are mainly "solvent residues". The solvent used for leaching is "No. 6 light gasoline", which some people tend to confuse with gasoline from gas stations. In fact, the No. 6 light gasoline used to leach grease is a "food grade" organic solvent based on n-hexane, with a boiling point of about 70 ° C, which is easy to remove by heating after extracting oil, which is far from enough to endanger health.
Verifier: Yun Wuxin 丨 Doctor of Food Engineering
Recently, there is an article circulating in the circle of friends, saying that a lot of cooking oil is soaked in gasoline, and eating too much will cause illness. The article also argues from various angles that "leaching oil will endanger health, while pressing oil is healthy and safe." This article uses a lot of professional terms and scientific terms, and also quotes a lot of professional content, which makes people "unclear". However, the entire article is actually selectively presenting facts and distorting interpretations, thus creating a "rumor article" that misleads the public. I'll break through them one by one.
First, why does the method of making edible oil replace the "extraction method" with the "pressing method"?
"Pressing" is the traditional process of extracting oil from oil crops, which is to separate the oil directly from the oil through physical pressure; while the "leaching method" is to soak the oil crop with an organic solvent, extract the oil into the solvent, and then separate and purify the edible oil.
The equipment and process of the pressing method are relatively simple, and the small workshops in rural areas can be completed, while the leaching law requires a modern production line, and the process is more complex. In terms of the efficiency of extracting oil, the extraction efficiency of the "leaching method" is higher than that of the "pressing method".
This significant difference in production efficiency makes most of the world's soybean oil now use leaching process, while oils with high oil content such as peanuts and rapeseed are pressed first and then leached, and only olive oil and other special flavors are fully pressed.
Second, the pressed oil "safe and hygienic" and the leaching oil "toxic and harmful"? This is a distortion of the facts
The rumor article claims that the pressed oil "does not have any chemical additives in the whole process, ensuring product safety, hygiene, no pollution, and natural nutrition is not destroyed", while the leached oil "is a low-nutrient, toxic, harmful and inferior oil that is not beneficial to the health of consumers, and cannot be used as a human 'edible oil', but can only be biofuels".
Image note: Screenshot of the web article
First of all, "no chemical additives" and "safe, hygienic, pollution-free" are two different things. Pressed oil needs to be heated to a higher temperature, and the temperature is further increased when pressed, resulting in large amounts of polycyclic aromatic hydrocarbons such as benzopyrene. In order to improve the oil yield, many oil mills will repeatedly roast the oil crops, forming more benzopyrene. In the leaching process, the temperature when extracting the oil is very low, and benzopyrene is basically not formed, but some will be formed during the refining process. In other words, whether it is pressed or leached, benzopyrene may be produced, and the amount produced is closely related to the specific process conditions. The leachable oil must be refined, and the content of benzopyrene can be reduced to a limited standard; if the pressed oil is refined, it can also be lowered, but the pressed oil can be eaten directly without refining (that is, "soil oil" and "self-pressed oil"), and the benzopyrene content may be much higher than the national standard.
As for the "leaching oil and residual aflatoxin B1", it is a complete rumor. Whether it is pressed or leached, no aflatoxin is produced during processing, and the aflatoxin in the oil comes from the oil raw material itself. Whether it is leached oil or pressed oil, aflatoxins are efficiently removed during refining, and those that have not been refined (i.e., "soil oil" and "self-pressed oil") will retain aflatoxin in the oil. In fact, there have been a large number of reports of "self-expelling oil" and "soil-pressed oil" aflatoxin exceeding the standard in the news, and basically no reports of aflatoxin exceeding the standard in the leaching oil have been seen.
The rumor article also declares:
Allegations of the safety of leaching oil are mainly "solvent residues". The solvent used for leaching is "No. 6 light gasoline", which some people tend to confuse with gasoline from gas stations. In fact, the No. 6 light gasoline used to extract grease is a "food grade" organic solvent based on n-hexane, with a boiling point of about 70 ° C, which is easily removed by heating after extracting oil. The so-called "food grade" refers to the treatment of removing heavy metals, and the content of harmful heavy metals is controlled within the range of less than one hundred millionth, which is far from enough to endanger health.
In the "crude oil" that is heated to remove the solvent, the content of n-hexane does not exceed 100 ppm (ppm is one part per million). This crude oil is further refined, and in the final edible oil obtained, the residual amount of the solvent is required as follows:
Image source: Soybean oil national standard GB/T 1535-2017
That is to say, solvent residues are no longer detectable in primary soybean oil, while solvent residues (i.e., GB2716 regulations) are no more than 20 ppm in secondary and tertiary soybean oils. This standard does not endanger health at all.
There is also a saying in the rumor article:
The solvent residue standard for "edible oil" mentioned earlier is actually the same as China's "first-class soybean oil" standard. The "frightening 500 mg/kg" mentioned later refers to soybean meal, not edible oil. "Edible soybean meal" refers to soybean meal used for further processing into other food raw materials (such as soy protein or soybean fiber), and is not directly consumed. Residual solvents are further removed during processing. As for animal feed, most of the limit standards are not as high as food. The so-called "so-called entry into the human body through the food chain" is purely unfounded imagination.
Leaching oils do remove more "trace nutrients," but they don't affect health
For the nutrition of leaching oil and pressed oil, the rumor article makes the following summary:
First of all, the nutritional value of edible oil is mainly "various fatty acids", the previous said that when pressing oil, "does not destroy unsaturated fatty acids such as linoleic acid" as an advantage, and later said that when leaching oil, it is said that "various fatty acids can only provide energy for the human body, basically no nutrition to speak of", a typical "double standard".
Secondly, there are no minerals worth mentioning in the cooking oil, and it does not matter whether it is "retained" or "destroyed". Only vitamin E and phytosterols in the "micronutrients" are worth paying attention to. Leaching oil does remove a significant portion of vitamin E and sterols when refined, while pressed oil generally retains more. However, the reasonable consumption of edible oil is about 30 grams per day, and the total amount of vitamin E and sterols obtained from it is also limited - more sources, or the ingredients themselves.
In other words, the nutritional advantages of "pressed oil" are overstated.
Trans fats are also often mentioned regarding the health effects of leaching oils. During the refining process, it is indeed possible to form small amounts of trans fat, generally in the range of 1% to 3%. According to WHO guidelines, controlling the intake of trans fats to no more than 2.2 grams per day has no significant health impact. According to the daily intake of about 30 grams, the trans fat in it does not reach 1 gram. The rumor article says that this is "the main source of Chinese trans fatty acid intake", which is intended to scare everyone, but in fact, it shows that there are basically no other sources of trans fat in the diet of Chinese, and this point in edible oil is significantly lower than the "recommended control amount", so there is no need to worry.
Fourth, the residual "glyphosate" in soybean products will not reach the amount of health hazards
The rumor article also cites the content of a TV show from many years ago to render the harm of leaching oil.
Illustration note: The web article is illustrated
The "poisonous stuff" mentioned in it refers to glyphosate.
Rumor articles say that the national standard does not stipulate the "maximum residue limit" of glyphosate allowed for soybeans or soybean oil, which means that glyphosate residues should be "none". In addition, it is also said that glyphosate is not included in the list of food additives, so if glyphosate is detected in soybean oil, it should be regarded as an "illegal toxic additive" and suspected of "committing the crime of endangering public safety by dangerous methods".
This is a completely wrong understanding of national standards.
First, in the International Codex Alimentarius (CODEX), the use limit of glyphosate in soybeans is 20 ppm, and the actual content is much lower than this standard.
Secondly, the glyphosate in soybean food is a "pesticide residue", not a "food additive", and naturally will not be in the list of food additives. The director and host of the TV program are neither professionals nor serious about the scientific facts, and they think that "toxic things are put into this oil", which is just relying on "a face of righteousness" to distort the facts and provoke the audience's emotions.
For this rumor article, the problem of pulling glyphosate is actually a logical confusion. Glyphosate is a herbicide that is not only used in genetically modified soybeans, but may be used in a variety of crops.
This article was edited by fycfeng
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