Studies have shown that long-term intake of waste oil will cause obvious harm to human body, such as developmental disorders, enteritis, hepatomegaly, heart and kidney enlargement and fatty liver. Aflatoxin, one of the main hazards in gutter oil, is a strong carcinogen, and its toxicity is 100 times that of arsenic. Another question is ethical. Can you eat the oil that others have eaten, which goes bad in the sewer and is fished out again?
　　So, is there a simple way to identify gutter oil? We might as well listen to what food science experts and insiders say.
one
There is no good way to scientifically identify waste oil at present.
　　In an era of paying attention to food safety, the ideal state is that when you go to a restaurant, you take out a test paper and dip it in the dish. After a while, you take it out and compare it with the spectrum table, and then shout, "Boss, change the oil!"
　　However, the reality is that up to now, scientists have not found an ideal means to detect and identify gutter oil.
　　"Oil mixed with oil, fairy sorrow, fairy is difficult to separate it. Waste cooking oil has a history of more than 20 years. Even today, we can still see waste cooking oil in rural markets and urban-rural junction markets, and we also feel that it has entered the dining hall. If calculated by tonnage, there should be millions of tons of waste oil digested every year. I am very embarrassed. We can’t find a very effective technical means to identify it. This oil is gutter oil, and this oil is not gutter oil. " When attending a CCTV program, Hu Xiaosong, vice president of the College of Food Science and Nutritional Engineering of China Agricultural University, once said this.
　　Hu Xiaosong pointed out that the current detection methods have not overcome this technology and cannot scientifically distinguish the quality of oil, but the Ministry of Science and Technology has set up a special project for this matter, and I believe that it will be possible to distinguish the quality of oil by scientific means in the near future.
2
Traditional detection methods have certain limitations.
　　In the view of scientific researchers, the difficulty in treating gutter oil lies in that it is difficult to distinguish gutter oil from ordinary oil only from appearance and sense after refining processes such as washing, distillation, decoloration and deodorization. Illegal traders will also mix waste oil into edible oil, and if the content is small, it is even more difficult to detect.
　　He Dongping, a professor at the School of Food Science and Engineering of Wuhan Institute of Technology, has been engaged in the research of gutter oil for many years. In He Dongping’s view, the traditional detection methods only grasp a certain characteristic of gutter oil, and no method can effectively detect gutter oil from different sources at the same time, which sometimes leads to a large detection error and more possibility of misjudgment.
　　Wang Le, a graduate student of Wuhan Institute of Technology, once developed a blue test paper. With the increasing proportion of waste oil, the blue test paper will show yellow-green, light yellow and bright yellow. This is based on the "accumulation" of oil to detect the purity of oil, but this method is also limited by the proportion of waste oil added.
　　On the Internet, you can find a company specializing in the production of "Quick Detection Kit for Waste Oil", but from the instructions provided by the company, "for some unpurified oils (such as sesame oil, pepper oil, etc.) and oils with other ingredients (such as Chili oil), this method is easy to produce false positives".
three
Identify the waste oil refrigerator?
　　Senior chef Feng Peng, who once worked as a chef and executive in many big restaurants in Beijing, said that under normal circumstances, gutter oil and ordinary oil can’t be distinguished, and it is inevitable to be fooled when purchasing. He can only judge by practice: restaurants usually need to oil before cooking. In this "lubricating oil" process, good oil can be used seven or eight times repeatedly, while waste oil will become sticky and have a spicy taste after being used for up to three times.
　　"In addition, when the outdoor temperature is low, waste oil will solidify like palm oil, so people often use waste oil to pretend to be palm oil." Feng Peng said that gutter oil can be identified in winter and can be tested in the refrigerator in summer. Some media think that gutter oil has a taste and can be smelled out. In addition, it contains a lot of water, and the pot will explode. Feng Peng thinks these are nonsense, because water can’t be mixed into oil at all, and gutter oil has no odor.

four
How should we identify waste oil?
　　Take a look. Look at the transparency, pure vegetable oil is transparent, and the transparency will decrease due to the mixing of alkali grease, wax and impurities in the production process; Look at the color, pure oil is colorless, and the oil will be colored because the pigment in the oil is dissolved in the oil in the production process; Look at the sediment, its main component is impurities.
　　Second smell. Each oil has its own unique smell. You can drop a drop or two of oil on your palm, rub your hands together, and smell it carefully when you are hot. Oil with odor indicates that there is a problem with the quality, and it is likely to be waste oil with odor; If there is a smell of mineral oil, you can’t buy it.
　　Three tastes. Take a drop of oil with chopsticks and taste it carefully. The oil with sour taste is unqualified, the oil with bitter taste has been rancid, and the oil with peculiar smell may be waste oil.
　　Listen. Take one or two drops of oil from the bottom of the oil layer, coat it on flammable paper, light it and listen to its sound. The products with normal combustion and no noise are qualified products; If the combustion is abnormal and makes a "squeaky" sound, the water content exceeds the standard and it is an unqualified product; The "crack" explosion during combustion indicates that the water content of the oil is seriously exceeding the standard, and it may be adulterated products, so it is absolutely impossible to buy.
　　Five questions. Ask the merchant about the purchase channel, ask for the purchase invoice or check the sampling test report of the local food hygiene supervision department if necessary. (Comprehensive by this newspaper)

　　If the empire is understood as a conquest system composed of suzerain and conquered areas, then China has never been an empire. China established a unified centralized country in the Qin Dynasty. Although Ying Zheng claimed to be the "emperor", this unified country was not an empire. China has been the vertical rule of the county system since the Qin Dynasty. All officials are appointed by the imperial court, and there is no entrusted management. As Han Feizi said, China’s ancient state structure is "everything is in the four directions, and it should be in the central government, and the saints should insist on it, and the four directions should be effective". After Qin destroyed the six countries, the whole country was divided into thirty-six counties. From then on, the central government of China was not composed of localities, but was divided by the central government. The central government precedes the local government in logic and time. All the ruling power of the country comes from the central government, and the local government does not have any inherent power. The place is the agency of the central government, and the central government is "like an arm, like an armband" to the place. Therefore, there has never been an empire in the history of China, and the concept of empire has never appeared in the language and writing of China.

　　▲ The situation map of the Qin Dynasty. (Source: Outline of Chinese and Foreign History)

　　▲ Situation map of the Western Han Dynasty. (Source: Outline of Chinese and Foreign History)

　　▲ The map of the territory and frontier nationalities in the early Tang Dynasty (669 years). (Source: Outline of Chinese and Foreign History)

　　At the same time, the ancient Central Plains civilization in China also promoted the homogenization within the unified country. The ancient Central Plains civilization in China is a powerful cultural soft power to attract and integrate the surrounding ethnic groups. Mencius called it "changing foreigners with summer". After the Han Dynasty, people often use Sinicization to explain the process of homogenization of unified China by Central Plains civilization. This is also fundamentally different from the empire where various heterogeneous civilizations coexist.

　　▲清朝疆域图（1820年）。（图片来源：《中外历史纲要》）

　　如上所述，在西方政治话语和学术语言中，帝国是一个由中央地带与从属地带共同组成的征服体系。如果把中国古代王朝的强盛时期称之为帝国，就意味着中国在古代曾经是一个征服体系。西方一些学者常常把中国的清王朝称之为帝国，认为清王朝的疆域是一个征服了多个领土、多个民族的多层次体系，疆域内各个民族、各个地区都是帝国的板块，只是暂时被清王朝用武力所统治。按照这种观点，清王朝崩溃以后，帝国的一些板块就应当独立出去，就像当年沙皇俄国崩溃以后，各个板块独立出去一样。所以，如果承认清王朝是帝国，就意味着中国的边疆是被清王朝征服的，清王朝一旦崩溃，这些由不同种族构成的边疆地区就应当独立出去。这也是为什么一些西方人支持中国的西藏、新疆独立的原因之一。所以，中国在清代不是一个帝国，这不仅是一个理论问题，而且也是一个重要的现实问题。

　　▲ Schematic diagram of the Western Zhou Dynasty. (Source: Outline of Chinese and Foreign History)

　　▲ Map of the Warring States Period. (Source: Outline of Chinese and Foreign History)

　　In China academic circles, some scholars have seriously discussed the concept of empire. But even among some scholars who try to clarify the concept of empire, there are still some vague understandings. For example, some scholars denied that there had been an empire in China since the Qin and Han Dynasties, but they still understood the Zhou Dynasty before the Qin Dynasty as an empire, on the grounds that the Zhou Dynasty’s local rule was not direct, but indirect, which was similar to the western empire. In fact, this is also an inaccurate understanding of the political structure of the Zhou Dynasty. There is no doubt that the centralized political structure of the Zhou Dynasty is fundamentally different from that of the Qin and Han Dynasties. But this difference is not the difference between an empire and a centralized dynasty, but the difference between a feudal system and centralization of authority.

　　The Zhou Dynasty in history was not a conquest system, but a enfeoffment system formed by the supreme ruler Zhou Tianzi. Within this system, more than 70 feudal vassal States were not conquered and established by the Zhou Dynasty, but were enfeoffed by the Zhou Dynasty according to the merits of being close to each other and defeating the Shang Dynasty. The people of these vassal States were all Chinese. The national political structure of China in the Zhou Dynasty was similar to the feudal system in the Middle Ages in Western Europe, but it was fundamentally different from western empires, such as Alexandria and Rome.

　　What needs to be clarified is that in history, China’s national structure seems to be similar to that of western empires in some aspects. In the history after Qin and Han Dynasties, China’s imperial court sometimes ruled the border areas loosely, and sometimes it ruled indirectly instead of directly. For example, the chieftain system in the remote areas of China once existed widely, which was called "Jimi system" in ancient times. If ancient China was not an empire, how can we understand that this national structure is similar to the empire?

　　Personally, I think the most fundamental difference is that China’s idea of unification is totally incompatible with the idea of empire. China’s national construction has a set of political ideas, political theories and a political belief, which is China’s idea of great unification. This idea mainly comes from Legalists and Confucianists, although the two most influential schools in China often argue with each other. China’s system since Qin Dynasty is Confucianism, and the basic framework and system of the country are based on the principle of Legalism, which is embodied in the centralized county system, which is called "the political system of Qin Dynasty is practiced in all generations"; Confucianism, on the other hand, provides the society with general ethics and moral norms, maintains the relationship between people, and also regulates the relationship between monarch and minister.

　　There is indeed a real problem here. In ancient times, it was really difficult for the central government to implement unified vertical rule in a huge territory. Due to the low productivity in ancient times, such as the level of material development, traffic roads and tools are very backward. This has indeed caused great difficulties to the unified national governance. In the political centers of ancient China, such as Chang ‘an, Luoyang and Peking, it was difficult to implement vertical rule in the border areas. It takes several months to go to Beijing from Guizhou, Yunnan, and vertical management is of course very difficult. However, after Qin and Han Dynasties, unification has become the consensus of Confucianism and Legalism. So from the Qin and Han dynasties, a new system was used — — To manage the border areas by the system of detention. The system of detention is an expedient measure. When the central government is unable to reach the local level and has no way to directly rule, it can temporarily give the place of detention autonomy, similar to the empire’s rule over the conquered place. The system of detention is relatively loose, such as the toast system in the ancient frontier areas of China. You can manage yourself by paying tribute and being loyal to the court.

　　▲ The Hailongtun Tusi Site in Zunyi, Guizhou Province is listed as a world cultural heritage. It is an important place for Tusi Yang in Gubo Prefecture, and witnessed the heyday of the Tusi system. (Source: vision china)

　　So, does this mean that the detention system is the same as imperial rule? In fact, the difference is very big. China’s thought of unification has been deeply rooted in people’s hearts since Qin and Han Dynasties. Due to the constraints of realistic conditions, the central government can give local governments a lot of autonomy at some time, but these autonomy rights are by no means inherent in local governments. The central government can grant local governments a great deal of autonomy, but because the source of law lies in the central government, the central government has the right to take it back when conditions are ripe. This is the change of soil into the stream in the history of China. This is not the same as the empire. China’s thought of unification has penetrated into the marrow of rulers and literati, and is the core of China’s political culture.

　　Therefore, for more than two thousand years, China’s detention system is a supplement to the centralized unified system, and the central government has unified all the territories through a set of very complicated and elaborate designs. Sometimes, ancient China looks like an empire on the surface, and even some frontier areas have greater autonomy than the subordinate areas of the empire. However, in China, all the power in the border areas is granted by the central authorities, not the local authorities, and the local authorities have no inherent power. That is to say, the unified county system has never been a conquest system outside the country, although it can’t fail to reach the surrounding boundaries for a while. For the central court, all the border areas have been brought into the unified national framework.

　　Therefore, from the formal point of view, there are essential differences between the system of imprisonment and the imperial system under the framework of China’s ancient unification. I think it’s necessary to distinguish between the empire and the fetter system in our history. If we don’t make a distinction, it will cause great confusion and threaten the state structure of China now. Of course, the comparative study of the captive system and the imperial system still needs a lot of work, which requires a lot of detailed analysis.

　　About the author:

　　Han Zhu, director of Shangdao Society Research Institute, researcher of China Research Institute of Fudan University, and columnist of Observer Network. In the 1980s, he taught western philosophy in China universities. In the early 1990s, he did research on comparative politics and the development of contemporary China in new york University and Columbia University. He has published works such as China Power and Historical Genes of China Road.

　　Producer | Yang Xinhua

　　Overall planning | Hu Jun, Liu Jia

　　Writing | Yang Chao

　　Editor | Guo Hui

　　Production | Hu Qi