Oil is mixed with oil, it is a fairy tale-when many consumers choose to "temporarily control their mouths" due to the incident of gutter oil, experts are also frowning on how to get out the gutter oil. Worrying is because there is no authoritative and effective way to see through all the drainage oils—because of the diverse sources, complex composition, and different blending ratios, there are ever-changing non-standard samples in front of the experts.
Is this kind of oil after a simple "face change" in an underground workshop really "difficult to distinguish"? Yesterday, the reporter asked the industry for advice. Experts generally believe that drainage oil is not unfathomable. How to extract drainage oil quickly and accurately is indeed a new issue facing the scientific community.
Existing technology is inaccurate and has blind spots
The usual appearance oil of "looking" has its own origins: greasy floats in the sewer, swill oil extracted from leftovers, and waste oil from repeated frying in fast food restaurants. These misguided kitchen wastes were originally unsightly, but after reprocessing such as washing, distillation, decolorization, deodorization, etc., they actually obtained a "new life": they usually blended with new oil in a certain proportion, and then returned to Restaurant table.
Based on human senses alone, the color, aroma, and taste of drain oil are almost the same as those of ordinary cooking oil. Even instruments with proven details are often "fooled"-from the analysis of the main components, the corresponding oil is still "triglycerides", which is no different from ordinary oils.
Isn't there any "horse foot" left in the life trajectory of repeated processing of gutter oil? Of course there is. During the cooking process, salt, MSG and other ingredients will be fully fused with edible oil, and metal ions will be mixed in it. In the wok, vegetable-derived edible oil will inevitably mix with animal fats such as meat, resulting in a sudden increase in cholesterol content .
As a result, some single index detection methods have been born. For example, three years ago, Liu Zhijin, a student of Wuhan University of Technology, used the relationship between the concentration of metal ions and electrical conductivity to find that the electrical conductivity of "Shuishui Oil" was 5-7 times that of first-grade edible oil. A half-hour identification method to identify the oil of the drain. However, the method of staying in the paper was finally shelved by the unavoidable misjudgment.
Huang Fenghong, a researcher at the Institute of Oil Crop Research of the Chinese Academy of Agricultural Sciences, told reporters that there are actually many methods for detecting gutter oil, but the existing technology has more or less certain blind spots, and the accuracy rate needs to be improved, which is not enough to serve as a supervisor. "Judge". In general, the conductivity method is suitable for blending oil with a drainage oil content of more than 20%, while the cholesterol method requires a drainage oil content of more than 10%.
"Fingerprint Atlas" is expected to be introduced in the new method
Are experts really at a loss when dealing with gutter oil? In the future, will it be possible to expose gutter oil with a piece of test paper like detecting pesticide residues in vegetables? Industry insiders say that at the moment, we need to find a significant difference from gutter oil It is very difficult to use a single marker for common cooking oil. In other words, it is difficult to smell the drain oil with only one "nose".
So, is it possible to have two or three "noses"? "This is exactly the method we are going to try." Last year, the Ministry of Science and Technology of the People's Republic of China had set up a project to deal with the difficulty of detecting drain oil. Answerer. In their alternative answers, the "nose" of the joint search for "criminal evidence" is really a lot-in addition to conductivity, cholesterol, trans fatty acids, biological toxins and other indicators, the extremely sensitive "electronic nose" Fingerprints will be established for different oils and fats, and of course include gutter oil from different sources. Huang Fenghong said that the key research team will find out the interrelationships among multiple parameters from the intricate data, synthesize the judgments of multiple "noses", and finally determine the presence or absence of drain oil.
In fact, it has become a common idea for researchers to intercept drainage oil through various methods. Prior to this, some experts measured the content of gutter oil in edible oil within one hour based on the crystalline shape of different oils and fats in the frozen state, and then used analytical methods such as chromatograph and photometer.
Enterprises wait for the introduction of national standards
Using "ditch oil testing" to search for keywords on the Internet, the reporter found a biotechnology company registered in Fudan Science and Technology Park. According to reports, a rapid detection kit developed based on the principle of "thin layer chromatography" can be used to identify drain oil. On a set of comparison charts, a thin layer chromatography silica gel plate that had been exposed to suspected gutter oil showed a clear trailing spot. However, Gao Chenhao, the person in charge of the company, admitted that this "tail spot" can only be used for the initial screening of oil samples. For further "confirmation", follow-up analysis with laboratory instruments is required. At present, related instruments are in further optimization.
Gao Chenhao told reporters that a few years ago, the company started research and development of sewage oil detection technology, but the market response was dull, and few people have been interested. Recently, as the sewage oil incident continues to heat up, customers have come to ask one after another, but unfortunately there is no mature product in China. Right now, the company is positively soliciting samples of suspected drain oil from the society and providing free testing to continuously improve the accuracy of the kit.
"We hope that the country will introduce standards for gutter oil testing as soon as possible and clarify the specific markers in order to guide the systematic implementation of instrument identification." Gao Chenhao said
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