● purpose of the test

how to distinguish good from bad edible oil

● test supplies

bulk soybean oil (hereinafter referred to as soybean oil), bulk salad oil (hereinafter referred to as salad oil) and duck oil

● test location

Yipin Jiliang International Hotel

● tester

supervisor of Changchun Food and Drug Administration Green Park Branch. Jia Xiaolong, the chef of Yipin Jiliang International Hotel, and Xu Xigang, the chef for many years

● Experimental results:

After three different oils were heated and frozen, the heated duck oil had an unpleasant smell, and white grease was solidified on the frozen duck oil. (This test is only based on the oil purchased this time)

"How can we tell whether the oil we bought is good?" On June 6th, with the help of the supervisors from the Green Garden Branch of Changchun Food and Drug Administration and the chefs from Yipin Jiliang International Hotel, the reporter started this experiment on how to distinguish oil.

The reporter bought soybean oil, salad oil and duck oil at random in the market. Through the heating test, it was found that black substances hung on the container after heating soybean oil and duck oil, and soybean oil smelled like beans, duck oil smelled like fish, but salad oil did not change. White grease floats on the frozen duck oil, while soybean oil and salad oil remain unchanged.

Introduction to the experiment

Listen to the sound and distinguish the color when heating

Pay attention to the time when freezing

The reporter first poured half of the three oils into three white bowls respectively. Duck oil is dark yellow, and it smells a little fishy when you look down carefully. The color of soybean oil is slightly lighter than that of duck oil, and the color of salad oil is the lightest.

Chef Xu Xigang introduced that after buying oil, the quality of oil can be preliminarily distinguished by heating and freezing. When choosing the heating method to distinguish, we should pay attention to the sound and color change of the oil when it is getting hotter. If the oil makes a harsh crackling sound, it means that the purity of the oil is average, while if the color turns black gradually, it also means that the quality of the oil is not reliable.

If you choose the freezing method, you should pay attention not only to the temperature but also to the time. Generally, it is -8℃ and needs to be frozen for about 11 hours. If there is white grease on the frozen oil, it means that this oil may contain animal fat.

Two experiments

Heating salad oil hardly changed

Brush the pan and catch fire. Xu Xigang slowly poured salad oil into the pan and stirred the salad oil in the pan with a spoon. Xu Xigang said that in order to see the changes of these oils after heating, the oil temperature needs to be above 211℃, which is about 67% mature. After about 1 minutes, the salad oil was poured out. Salad oil was poured into the plate with a crackling sound. Lower your head to smell the smell, and there is no change from the salad oil that was not heated at first, but the color is slightly darker.

The soybean oil crackled

Xu Xigang changed another pot and poured the soybean oil into it. During the heating process, soybean oil has been making a "crackling" sound, and it will emit smoke, and there is a smell of oil smoke from time to time. After pouring into the plate, it is slightly lighter than the unheated soybean oil before, and smells a faint bean smell. After about 2 minutes, a lot of black substances adhered to the original white plate.

Duck oil has a pungent smell

When the reporter observed the change of soybean oil, Xu Xigang had already put the duck oil into the pot. In the heating process of duck oil, a pungent smell came out, which made people smell disgusting. After the duck oil was poured into the plate, the pungent smell became stronger and stronger, and around the inner wall of the plate, the same black substance as soybean oil appeared.

Xu xigang explained that these black substances are all formed in the process of oil refining. When there is no heating, these black substances will not be seen by people, but they will definitely appear after heating.

freezing

duck oil freezes white grease

In order to verify the accuracy of the test, the reporter decided to put the three oils in the hotel freezer first and wait until the next day to see the results.

At 11: 11 on July 7, the reporter returned to Yipin Jiliang International Hotel. In the kitchen, the chef took out three oils that had been frozen for a long time. After freezing, soybean oil turns orange and translucent, while salad oil turns pale yellow, duck oil turns milky white, and there is a circle of white grease on the top.

Jia Xiaolong introduced that common edible oil will solidify at -4℃ to -5℃. In order to achieve the best effect, they adjusted the temperature of the freezer to -8℃. During the freezing process, through their observation, it was found that duck oil was the first to be frozen. Jia Xiaolong said that because duck oil is animal oil, animal oil was originally solid in animals, but after being refined into liquid oil, it is very easy to solidify when it is cold.

Soybean oil solidifies faster than salad oil

Jia Xiaolong said that soybean oil was the second to solidify, and salad oil was the last to solidify in this experiment. Jia Xiaolong said that according to his working experience in 2112, edible oil with high viscosity solidified quickly. In this experiment, the viscosity of soybean oil is higher than that of salad oil, so soybean oil solidifies faster.

Test results

Duck oil is garbage oil

It contains carcinogens

It was found that duck oil not only emits a strong fishy smell when heated, but also has white grease on it when solidified.

The supervisor of Lvyuan Branch of Changchun Food and Drug Administration said that this kind of oil is the oil that seeps from ducks when some roast duck restaurants roast ducks, and it is inedible. Roast duck oil, like frying waste oil, belongs to garbage oil, which has lost its edible value and contains carcinogens. Supervisors said that after eating this garbage oil, there is generally no immediate disease or poisoning reaction, so some unscrupulous restaurant owners dare to use garbage oil. However, the harm of garbage oil to the health of consumers is long-term and chronic.

● Teach you a few tricks

Look, smell, listen and taste

You can identify oil

Supervisors remind the public that garbage oil can be easily identified as long as you pay attention to observation.

Look: Pure vegetable oil is transparent. If alkali grease, wax and impurities are mixed in the production process, the transparency will decrease.

smell: each oil has its own unique smell. You can drop one or two drops of oil on your palm, rub your hands together, and smell the smell carefully when you are hot. The quality of the oil with odor is problematic.

taste: take a drop of oil with chopsticks and taste it carefully. Oils with sour taste are unqualified products, and oils with bitter taste and peculiar smell can't be bought.

Listen: Take a drop or two of oil from the bottom of the oil layer, spread it on flammable paper and light it. The products that burn normally and make no noise are qualified products; those that burn abnormally and make a "squeaky" sound are unqualified products with excessive moisture; those that make a "crackling" sound when burning may be adulterated products, and you must never buy them.

the supervisor said that for some barrels of oil purchased by the public, it is also necessary to see whether the product name, ingredient list, quality grade, net content, factory name, address, production date, shelf life and other contents are indicated on the outer packaging, and there must be a QS mark.

fried food for many times

can distinguish good oil from bad oil

Jia Xiaolong said that the best way to distinguish whether the oil is good or not is to fry it. Take fried meat as an example. Good cooking oil can be fried for about 4 times, and the color will not change much. However, if you choose poor cooking oil and fry it for at most 2 times, the cooking oil will turn black.

Jia Xiaolong said that the best basis for distinguishing the quality of edible oil in his work is to observe whether the viscosity of edible oil is high. If the viscosity of edible oil is higher, it is not necessarily a good oil, and the lower the viscosity, the better its quality will be. However, the higher the viscosity of soybean oil and sunflower oil, the better. It is suggested that the general public must observe the transparency and viscosity of edible oil when choosing to buy edible oil, and then compare it repeatedly before buying it.