"Breakfast stalls, fried noodles and fried rice stalls, barbecue stalls, 90% of the use of gutter oil; red oil boiled series and deep-fried barbecue dishes, 50% contain gutter oil ingredients; semi-finished cooked food, boxed lunches, business packages, such as 30% of the gutter oil; but the steamed fish, seafood, soup, etc. does not contain gutter oil." --Shanghai media quoted a post by a netizen named "a certain light" on "starting from the gutter oil, teaching you how to order food", which immediately caused a large number of Shanghai netizens to respond enthusiastically upon publication.

The post was published on the website of a Shanghai-based netizen.

As a restaurant worker, he taught Shanghainese how to order food in order to reduce the chance of eating gutter oil.

The so-called "gutter oil" is in fact the oil salvaged from the "lower pool" of restaurants. Engaged in the Chinese food industry for several years, "a light" in the beginning of the post for the netizens to introduce the origin of the gutter oil.

He described the emergence of gutter oil from the late 1990s, when the environmental protection department in the approval of the catering license, the requirements of oil and water separation, that is, the hotel's wastewater, swill feet, oil residue separate, and gutter oil is from the hotel waste oil pool waste oil. The catering units are usually privately disposed of these waste oil, a new industry was born, that is, the waste oil recycling industry.

"A certain light" in the post revealed that the waste oil for the catering unit is garbage, even if someone recycling, the cost is very low, generally a large tin oil drum cost less than 20 yuan, and the difference between the genuine oil dozens of times. Businesses where profit is paramount will naturally want to increase their business income by reducing costs.

"A certain light" in the post teaches Shanghai people how to identify gutter oil, and describes the identification techniques from four aspects: color, packaging, taste, and first-class viscosity. However, some netizens have questioned the feasibility of the so-called identification method of "a certain light", because restaurants generally do not allow guests to enter the kitchen, and since they can not enter the kitchen, they naturally do not see what kind of oil is used.

The netizens are most concerned about whether some heavy oil dishes contain gutter oil, with 30 years of experience as a head chef, "a certain light" replied in the post that the possibility of using gutter oil in the red oil boiled series is at 50%, and that some white oil dishes are less likely to be eaten with gutter oil.

He said, because of the local cuisine is concerned about the thick oil and red sauce, the oil directly affects the flavor of the dish, if the business with gutter oil, diners are very easy to identify, which also reduces the chances of using gutter oil.