How harmful is gutter oil? Experts teach you how to identify it
Core tip: On July 19, 2010, the General Office of the State Council issued a document, deciding to organize pilot work for the resource utilization and harmless treatment of urban kitchen waste such as gutter oil. A year has passed, and due to the huge profits in the gutter oil industry chain, some people still take risks and engage in the "gutter oil" industry. What is gutter oil? Is there a way to identify gutter oil? How to identify gutter oil? With these questions, we connected with a professor from the College of Food Science, a senior nutrition expert, and a chef with many years of experience, hoping to find answers.
Professor Fan Zhihong from the College of Food Science, China Agricultural University: Gutter oil has no definition and cannot be detected.
Can gutter oil cause cancer? Professor Fan Zhihong said, it is unknown whether gutter oil is carcinogenic.
"Who has conducted experiments on gutter oil? Who dares to?" Professor Fan Zhihong said, "Many of the current online claims about the dangers of gutter oil are nonsense."
Professor Fan Zhihong said that what can be confirmed now is that oil that has been heated for a long time is harmful. This low-quality oil will damage the human stomach, intestines, liver, and cardiovascular system. However, because the state has not yet defined gutter oil, it is unknown whether this oil is the "gutter oil" mentioned online.
How to identify gutter oil? Professor Fan Zhihong said that the state currently has no method to identify gutter oil. There is no judgment method that can say this is gutter oil and that is not, so currently, gutter oil cannot be identified.
Professor Fan Zhihong emphasized that oil that lacks nutrients is already bad oil. The effective nutrients of normal oils should include vitamin E, essential fatty acids, etc. These two are the most important. Oils with low content or even without these two nutrients are already bad oils.
Inferior oil cannot be distinguished by the naked eye, but its greasiness can be used for judgment
Oil that cannot be washed off even with hot water is bad oil
Professor Fan Zhihong said that although gutter oil cannot be identified, this kind of bad oil that has been heated for a long time can still be identified. Oil that has been heated for a long time will feel very greasy and sticky. As for whether it is oil scooped from a gutter, there is no way to tell.
Among the methods for identifying gutter oil circulating online, they all mention looking at the color, saying that good oil is relatively transparent and clear. However, Professor Fan Zhihong said that the color can be solved by "decolorization methods", so it cannot be judged from the color.
However, the viscosity of the oil cannot be tampered with, so when eating in a restaurant, if the oil on the dishes is particularly greasy, and it is oil that cannot be washed off even with hot water, it is already very bad oil.
Senior nutrition expert He Yingqiang of China: The laboratory cannot detect all gutter oils
He Yingqiang said that the effective nutrients of normal oils are vitamin E and unsaturated fatty acids, and the most important in unsaturated fatty acids are essential fatty acids.
What harm will long-term consumption of low-quality oil have on the human body? He Yingqiang said that the harm caused by frequently heated low-quality oil to the human body is more obvious. High-temperature pyrolysis products may be carcinogenic. In addition, aflatoxin in moldy peanuts is carcinogenic. If moldy peanuts are pressed to make peanut oil, it will contain a certain amount of aflatoxin.
He Yingqiang said that China currently has methods to detect gutter oil, such as indicators for fatty acid rancidity, because the fatty acid rancidity indicators of low-quality oil do not meet the national standards. However, gutter oil contains a variety of chemical substances, and it is difficult for laboratories to detect all gutter oils. There is no detection method that can be applied to all gutter oils.
Is there a simple method to identify gutter oil? He Yingqiang answered that it is difficult to identify gutter oil with the naked eye in daily life. It is difficult to identify gutter oil by sight or smell.
Less animal oil, more vegetable oil
Be wary of vegetable cream containing trans fatty acids
From a nutritional perspective, He Yingqiang advises consumers to choose more vegetable oils. He said that saturated fat is harmful to the body, while vegetable oil is beneficial, so he recommends that consumers eat less animal oil and more vegetable oil.
In addition, many foods such as cakes, cream, and biscuits contain vegetable cream, which may be written as "hydrogenated oil" or "vegetable powder," "vegetary cream," etc. on the packaging. The state has not yet paid attention to the harm of vegetable cream, and consumers need to be vigilant and eat less food containing vegetable cream.
Expert: There is a simple method to identify gutter oil
1. Look at the color. Qualified oil is transparent, while gutter oil has various chemical components, which will be turbid and opaque, and there may be sediment at the bottom of the bottle. This kind of low-quality oil is often visible in bulk oil wholesale markets, and some small street restaurants may also use low-quality oil.
2. Smell the smell. Qualified oil will have the natural aroma of the oil itself, for example, peanut oil will have the fragrance of peanuts; olive oil will have the fresh fragrance of olives. Gutter oil does not have the natural aroma that oil should have. Smelling it carefully, you can smell a sour smell and a strange chemical smell.
3. Taste it. Usually, when buying oil, you use the color and smell to identify it, but after chefs buy the oil, they will use chopsticks to dip a drop of oil on their palm, rub it lightly, and then lick a little oil from the palm with the tip of their tongue. Normal oil will have a fragrant taste, for example, peanut oil will taste like peanuts, but gutter oil will taste sour and also bitter. The most commonly used method in the entire chef industry is these three simple methods. Consumers can also use these three methods to identify it in daily life, and do not eat oil that feels bad.
4. After eating. The oil used in dishes in restaurants is often tampered with, so it is very difficult to identify. But after eating dishes made with gutter oil, the stomach will feel bloated, and the stomach and intestines will feel uncomfortable, with a feeling of indigestion. This method may not be called a method, because you have to eat it first to have an adverse reaction.
Li Jiansen said that small street vendors and small restaurants generally use bulk, cheap oil to reduce costs, so the probability of using gutter oil is relatively high. When consumers dine out, they can choose larger restaurants with brands and good reputations, because their procurement channels for edible oil are formal and generally more reliable.