Can gutter oil pass the quality inspection? How is gutter oil detected?

It is indeed possible for the treated "gutter oil" to pass the quality inspection. After the illegal personnel take the "gutter oil", they will refine it. The basic process is:

First, the grease is heated and melted to wash away large impurities, and then "white clay" is added to precipitate fine impurities and adsorb peculiar smells, and then after many high-temperature treatments, the peculiar smells are removed and the acid value is reduced. In addition, after refining, "gutter oil" may be blended with edible oil in a certain proportion. In this way, according to the current "Sanitary Standard for Edible Vegetable Oil" (GB 2716-2005), the oil sample obtained may deceive the daily edible oil testing indicators (acid value, peroxide value, leaching oil solvent residue, free gossypol, total arsenic, lead, aflatoxin B1, etc.).

The composition of "gutter oil" is very complex. In a broad sense, "gutter oil" generally refers to the oil made from swill, grease trap oil, inferior meat offal and skin, kitchen re-frying oil, etc., which are simply processed and refined. The other components produced or mixed with different ** "gutter oil" are very different, making it a particularly complex sample for analysis and detection, and it is difficult to find its specific components.

At present, there is no national standard for testing "gutter oil", even if it is tested by the quality inspection department, it can only be suspected gutter oil, and it is ultimately up to the public security department to trace back to the source of oil production to determine that it is gutter oil. The unified deployment of the Food Safety Office, the Ministry of Health in conjunction with relevant departments has publicly solicited gutter oil detection methods, and recommended 4 large-scale instrument detection methods and 3 rapid detection methods, the accuracy has been greatly improved, and there is still room for improvement.

In view of the phenomenon that "gutter oil" can pass quality inspection, food safety expert Liu Qingjun said that there are currently some research methods, and the national quality inspection department can form a unified standardized testing method to facilitate the identification and screening of "gutter oil".

According to Xinhua News Agency, some oil refineries in Beijing, Tianjin and Hebei refine swill into gutter oil and filter it into clear salad oil, which flows to food processing enterprises, construction sites, wholesale markets and even supermarkets in the form of loose oil.

Liu Qingjun, vice president of the Beijing Academy of Science and Technology, director of the Beijing Physical and Chemical Analysis and Testing Center, is also a member of the Beijing Food Safety Expert Committee, yesterday he introduced that the acid value of "gutter oil" after filtration and purification may pass the test, just like melamine in the past, before the country only checked the protein content, and did not check whether there were illegal substances. All testing standards are formulated against normal food, and they are tested according to standardized indicators, and "gutter oil" cannot be distinguished.

Liu Qingjun pointed out that because "gutter oil" has been used, it generally contains table salt, which will produce sodium ions, as well as metal ions such as aluminum and iron. Beijing Food Safety Monitoring Center is currently studying the exploration method of detecting "gutter oil", and some researchers at Wuhan Institute of Technology believe that by testing the conductivity of the sample, the judgment of gutter oil can also be carried out (many experiments have shown that the conductivity of gutter oil is 5 7 times that of first-class edible oil), and some institutions have instruments for analyzing the proportion of "gutter oil" in edible oil.

Liu Qingjun therefore called on the national quality inspection department to form a unified and standardized testing method for "gutter oil", which should be promoted to various testing institutions to facilitate the identification and screening of "gutter oil".

There are two detection methods for detecting gutter oil on the Internet, which are sought after by many netizens**. The reporter interviewed food experts and learned that because the types and ingredients are very complex, the country's current testing of gutter oil is still under research, and there is no unified testing standard for the time being, and the test methods spread on the Internet are even more unreliable. x0d x0a A message went viral in major QQ groups and post bars, and this message introduced two methods for detecting gutter oil.

One is to put the cooking oil in the refrigerator for 2 hours, if there is white foam, it is gutter oil; The second is to quote a Chinese medicine practitioner: "The easiest way to detect gutter oil is to put a peeled head of garlic (garlic) in the stir-fry, which is most sensitive to aflatoxin." If the garlic turns red, it is gutter oil, which contains a lot of aflatoxin.

According to the analysis of experts from Wuhan Food and Cosmetics Research Institute, the online detection method is not reliable. After the storage temperature of the vegetable oil in the liquid state is lower than a certain point, the triglycerides in the edible oil will produce crystals, and the liquid oil will turn into solid fat, which is commonly called "freezing". When the temperature rises or heats up, the oil slowly turns to a liquid state.

One is the oil after repeated use such as boiled fish and hot pot bottom; the second category is oil made from sick and dead pork; The third category is old oil that has been fried repeatedly. Because the formation process of gutter oil is complex, there are many possibilities for mixing harmful substances in the process, and the previous oil hygiene standards only have a few indicators, and the gutter oil can be qualified after some treatment and testing, which brings many difficulties to the detection of gutter oil. Experts from the Ministry of Health have repeatedly argued on the various methods, but it is still difficult to find a simple way to distinguish them.

At the same time, experts pointed out that testing is only the last pass, and the focus of curbing the flow of gutter oil to the table is still strengthening supervision.

There is a trick to identifying gutter oil, and it would be a pity not to know.

Edible vegetable oil can generally be identified by seeing, smelling, tasting, listening, and asking.

1 look: look at the transparency, pure vegetable oil is transparent, in the production process due to the mixing of alkali lipids, waxes, impurities and other substances, the transparency will decrease; Look at the color, the pure oil is colorless, in the production process because the pigment in the oil is dissolved in the oil, the oil will be colored; Looking at the precipitate, its main component is impurities.

Color contrast. 2. Smell each oil has its own unique smell. You can put a drop or two of oil on the palm of your hand, rub your hands together, and smell it carefully when it is hot. If there is a peculiar smell of oil, it means that there is a problem with the quality, and the smell is likely to be gutter oil; If there is a smell of mineral oil, you can't buy it.

3TasteTake a drop of oil with chopsticks and taste it carefully. Oil with a sour taste is an unqualified product, oil with a burnt bitter taste has become rancid, and oil with a peculiar smell may be "gutter oil".

4 Listen to a drop or two of oil at the bottom of the oil layer, apply it to a flammable piece of paper, light it and listen to its sound. Qualified products are those that burn normally and silently; If the combustion is abnormal and makes a "squeak" sound, the moisture exceeds the standard, and it is an unqualified product; When burning, it makes a "crackling"** sound, indicating that the moisture content of the oil is seriously exceeded, and it may be an adulterated product, and it should never be purchased.

5. Ask the merchant's purchase channel, and ask for the purchase invoice or check the sampling test report of the local food safety supervision department if necessary.

In addition, the relationship between the concentration of metal ions and the conductivity of the oil can be used to determine the amount of metal ions in the oil by measuring the conductivity of the oil. Many experiments have shown that the conductivity of water oil is 5 to 7 times that of first-class edible oil, so that water oil can be accurately identified.

There is a trick to identifying gutter oil, and it would be a pity not to know.

Friends who have used animal oil know that animal oil will condense into solids.

Ninghai** found a large iron pot in a small forest, someone was roasting gutter oil, and finally these rough processed primary refining oil was "packaged" and shipped to the Green Company in Shandong, where the gutter oil was refined and finally flowed to the market and to the dining table (see this newspaper's report yesterday).

These dirty and smelly gutter oils have been transformed into food oils, and some have been transformed into big brands of edible oils, which are no different from real food oils in appearance.

Some people say that it can be distinguished by taste and color, but in fact, at present, the gutter oil processing technology of criminals has been "perfected". Like the gutter oil refining process, it is mainly a process of decolorization and deodorization, so as to achieve the same appearance and taste as real food oil. There is a lot of waste oil from hot pot restaurants, etc., which contains a lot of chili peppers, so in the process of removing the taste of gutter oil, spicy removal is the most critical step.

In addition, because the gutter oil is extracted from the dirt dug out of the sewer and oil pool, it also contains other mildew smells, such as the Green Company's finishing process, deodorization is also a key part of the solution.

In the process of gutter oil processing, another decolorization problem is also very critical, such as the oil collected from various dirty channels, although the color is incomparable with the authentic food oil after the initial refining, Green Company also adds pigments to these gutter oil to achieve the same effect as the color of the real food oil. But no matter how these underground processing gutter oil companies operate, there is one technology that cannot be achieved at present, and that is the separation of animal and vegetable oils. Gutter oil contains two components: vegetable oil and animal oil, that is, saturated fatty acids and unsaturated fatty acids.

It is understood that at present, even if the separation technology is good, it can only reach the limit of 15%, that is, in a bottle of food oil refined from gutter oil, 85% is vegetable oil components, and the remaining 15% is animal oil components, due to the heavy saturated fatty acids, often 15% are precipitated at the bottom of the bottle.

The biggest difference between saturated fatty acids and unsaturated fatty acids is their respective forms at a certain temperature, the former condenses into a solid, and the latter is still a liquid.

How to identify if there is a problem with the edible oil we buy from the market?

Yesterday, we interviewed the police who handled the case, and he said that there is a simple way to put the oil bottle in the refrigerator compartment, and after a few hours, you can find out if there is any sediment at the bottom of the oil bottle.

Here I want to tell you that palm oil will also precipitate, but if you buy peanut oil, rice oil, etc. in the market, the above refrigerated identification methods can be applied.

First, judging from the color, the gutter oil has impurities and is not transparent. Second, smell the smell, the gutter oil will have a sour or strange smell. It's all basic. It is also the most practical. It is recommended not to eat roadside snacks, for the sake of health, hehe.

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Gutter oil can also be detected quickly and accurately by measuring the conductivity of the oil by measuring the amount of metal ions in the oil by using the relationship between the concentration of metal ions and the conductivity. Many experiments have shown that the conductivity of water and oil.

A simple identification method for gutter oil.

At present, the detection of gutter oil should be done by professional and technical institutions, and the sensory, moisture content, acid value, peroxide value, carbonyl valence, iodine value, metal pollution conductivity and sodium ion content are measured. For individuals, there are the following six identification methods: provided by Shenzhen Shidejia Technology and Southern Reference Materials Network

Look at the color. It mainly depends on the transparency and color of the oil. Unrefined gutter oil is dull and cloudy in color, with a slightly dark red color.

Smell the smell. If the processing technology of the gutter oil is low-level, you can smell the smell of rancidity.

Taste the taste. Gutter oil can be sour, hala, spicy, and may also have a burnt taste.

Identify odors. Take a small amount of cooking oil in the palm of your hand and rub it back and forth with your palm, if there is a peculiar smell in it, it is likely to be mixed with gutter oil;

Water measurement. The moisture content of gutter oil generally exceeds the standard. You can take a drop or two of oil from the bottom of the oil layer, apply it to a flammable piece of paper, light it and listen to its sound.

Qualified oil is one that burns normally and silently; If the combustion is not normal and makes a "squeak" sound, and the moisture exceeds the standard, it is likely to be an unqualified oil.

Check the channel. Inquire with the seller and confirm the purchase channel of edible oil.

Ask**. Edible oil has a certain cost, and if the oil is too low, there is likely to be a problem.

Put it in the refrigerator: Put the oil in the refrigerator in the refrigerated area of 5 to 8 degrees Celsius, if there is white precipitation, it is likely to be gutter oil. Because in the process of processing edible oil from gutter oil, the suspect has not yet solved the technical problem of separating vegetable oil and animal oil;

High fire: If the color of the oil changes after firing at high heat, and the color becomes thick and black, it is likely to be gutter oil, because the small particles contained in gutter oil are easy to change color after being burned.

Sensory identification of gutter oil.

One look: look at the transparency, look at the color. The color is dark, relatively turbid, and there is sediment, and it may be gutter oil that is easy to solidify at low temperature.

One of the test tips is to pour a little oil on the popsicle, the oil quickly solidifies and adheres to the popsicle, it is likely to be made of gutter oil. The second trick is to pour a little oil over the glass, if the oil flows very slowly, there may be a problem.

Second smell: Each oil has its own unique smell. You can put a drop or two of oil on the palm of your hand, rub it with your hands together, and smell it carefully when you are hot. The smelly, faint hala smell is likely to be gutter oil.

Three tastes: Take a drop of oil with chopsticks and taste it carefully. The oil with a peculiar smell may be gutter oil, and the oil containing gutter oil is not fragrant, and the residual oil residue is black charcoal.

Four listening: Take a drop or two of oil from the bottom of the oil layer, apply it to a flammable piece of paper, light it and listen to its sound. If the combustion is abnormal and makes a "squeak" sound, the moisture exceeds the standard, and it is an unqualified product; When burning, it makes a "crackling"** sound, indicating that the moisture content of the oil is seriously exceeded, and there is a possibility of adulteration of the product, so it should never be purchased.

Five questions: ask the merchant's purchase channel, and ask for the purchase invoice or check the sampling inspection report of the local food safety supervision department if necessary.

Physical and chemical examination of gutter oil.

Moisture content, specific gravity, refractive index, saponification value, acid value, carbonyl value, peroxide value, iodine value, heavy metals, relative unsaturation of fatty acids, cholesterol, residue detection, oxidation product detection, conductivity of gutter oil, etc.