Many people know the Pu'er tea health benefits. But recently, Pu'er tea has been pushed to the forefront, due to a statement that Pu'er tea causes cancer. People who hold this statement claim that aflatoxin is found in Pu'er tea, and people drinking Pu'er tea will cause cancer quickly. Is aflatoxin commonly detected in Pu'er tea? Can we still drink tea in safety?
As for this, I contacted the academician Chen Junshi, an authoritative scientist in the field of food safety in China. He believes that aflatoxin detected in Pu'er tea is not a common phenomenon. Furthermore, experts from domestic authorities have already carried out the risk assessment with clear conclusions in the possible result of the detection.
Is aflatoxin detected in 100%? The conclusion is likely to be wrong.
To explore whether aflatoxin in Pu'er tea will endanger health, firstly you need to know whether aflatoxin will be commonly detected in Pu'er tea.
This problem is more complicated than everyone has thought. The survey known to everyone in early was conducted by the Guangzhou disease control and prevention center. The research and sampling were in 2009 with a total of 70 samples, all of which were detected with aflatoxin B1. This survey was reported by the media in 2010. As a hot spot in public, Zhu Wei, a Ph.D. student in the Department for the toxicology test of Guangzhou center for disease control and prevention, publicly explained on the TV that the price of tea in sampling is 4-15 yuan per kilogram. The sampling is inferior to Pu'er tea and even some of them are of the musty smell. There is no such tea in regular shops and supermarkets.
Besides, a survey of a master's degree student at Nanchang University was similar in 2012. All of the samples are inferior quality Pu'er tea, and the test results were all positive.
There are more surveys of mycotoxins in Pu'er tea, but they have produced quite different results. For example, in 2014 the Liwan District CDC in Guangzhou purchased a random sample of Pu'er tea from the wholesale market. 8 of 140 samplings were detected in aflatoxin B1 with a detection rate of 5.7%. In other words, Pu'er tea with no aflatoxin in samples accounted for 94.3%.
In 2014, a study from Zhou Hongjie, a professor at the Yunnan Agricultural University, took 15 samples in different types of Pu'er tea from different locations in Yunnan, including samples that had been exposed to moisture, but none of them was detected in aflatoxins. Some people will suspect the credibility of the survey in China. But In 2013 Australia’s institution analyzed 8 mycotoxins from 36 samples of Pu'er tea, and no aflatoxins were detected.
It shows that the conclusions of different surveys are at two extremes. One of the explanations is that the survey in Guangzhou CDC and master's thesis at Nanchang University is based on inferior tea. The result in the sample can not reflect the overall situation of Pu'er tea in the market.
However, this argument is also not accurate. The sampling of the Guangzhou CDC is from different warehouses. Although it is inferior, it is not all moldy samples. Besides, in 2014 Zhou Hongjie's surveys were not detected with aflatoxin in samples, including three samples in mold Aflatoxin and one damp sample dried by three times. This shows that mold is not necessarily the "Aspergillus flavus".
Zhou Hongjie believes that 100% detection of positive is incredible. The problem involves the method of detection. The 100% positive project mentioned above uses the detection method of ELISA (enzyme-linked immunosorbent assay), because the interference of phenolic substances in tea produces false positive problems. That is to say, if this detection method is used, it is necessary to remove the interference of phenolic substances to obtain accurate conclusions.
It can be proved that in recently, the Shenzhen Institute for Metrology and Quality Inspection officially issued a document. It stated that tea detected with aflatoxins, caused by no standard in the methods of detection, was misrepresented on the Internet. In the old standard of detection in aflatoxin B1, the sample without contained aflatoxin can be easily regarded as positive in the result. These loopholes of detection have been revised in the latest version of the standard in 2016. The new standard was implemented on June 23, 2017.
Besides, the article also said that the Shenzhen Institute for Metrology and Quality Inspection tests 15,000 batches of samples in aflatoxin each year, and did not find aflatoxin B1 in tea during annual risk monitoring and daily inspection.
Chen Junshi, a researcher at the National Food Safety Risk Assessment Center and an academician of the Chinese Academy of Engineering, said that a comprehensive analysis of these different surveys should be drawn into a conclusion. Pu'er tea without aflatoxins in detection is impossible, but at least the tea with aflatoxins is not a common phenomenon in detection.
The process of production in Pu'er tea is not suitable for producing aflatoxin
The analysis of the key processes in how to make Pu'er tea can also reveal some truth. The production of a modern method in Pu'er tea will shorten the production cycle through a method called pile fermentation, but it needs to maintain the quality of Pu'er tea in production. The so-called pile fermentation is a process of solid-state fermentation, which involves many types of microorganisms. It has been studied very clearly. The early stage of fermentation mainly appears Aspergillus niger and Rhizopus, and in later it later appears Aspergillus niger, Penicillium and yeast. These strains are not harmful to health. Aspergillus niger is the main dominant strain in the fermentation process, accounting for about 80% of the total number of microorganisms.
Studies have also shown that when Aspergillus niger and Aspergillus fumigatus are contained in the cultivation, the growth of Aspergillus flavus produced aflatoxin is inhibited. Besides, certain compounds contained in tea, such as tannins, caffeine, etc., can inhibit the production of aflatoxins. Experiments have shown that 86% production of aflatoxin can be inhibited when the caffeine content reaches 0.5 mg/ml, and the production of aflatoxin is completely inhibited when the caffeine content reaches 2 mg/ml.
In 2003, in Taiwan, there were also so-called rumors about Pu'er tea, named poisoning Taiwan. As to this, Professor Sun Luxi at Taiwan University sampled 44 samples of Pu'er tea on the market. No aflatoxins were detected in tea. They also did an experiment to inoculate Aspergillus flavus in Yunnan sun-green tea, and simulate the process of pile fermentation. But only sterilized group A was detected aflatoxin, and the content was very low (1.05 μg/kg). The remaining B and C groups were not detected sterilized. This experiment shows that under normal conditions, Aspergillus flavus is not easy to breed in tea.
Chen Junshi analysis and believes that from the current study Pu'er tea is not a material suitable for the production of aflatoxin, and aflatoxin is not produced in Pu'er tea under normal conditions.
Chen Junshi said that if aflatoxin is detected in Pu'er tea, it may be the result of poor conditions in the circulation of Pu'er tea contaminated with Aspergillus fumigatus. And the temperature and humidity are suitable for growing Aspergillus flavus. And it can multiply to produce aflatoxin. However, the pollution problems in circulation encountered in many foods, and it needs to be guarded and controlled.
The conclusion that drinking Pu'er tea can trigger liver cancer in people is not valid.
In any conditions of the process and production, consumers hope that the food they buy is safe and will not endanger health. However, in reality, people are exposed to carcinogens found in air, water, and food included cigarettes, bacon, alcohol, and Beijing roast duck. Whether it will have a bad effect on health depend on the frequency and amount of intake.
Chen Junshi said that in 2010 after the Guangzhou CDC reported aflatoxin in Pu'er tea, the experts of domestic authorities conducted a scientific evaluation on the health effects of aflatoxin in Pu'er tea.
This assessment concluded the highest level of aflatoxin B1 in Pu'er tea at 8.52 μg/kg. The assessment was concluded with a consideration of the condition that roughly half of the aflatoxin will be dissolved from the tea leaves into the tea soup and the tea was drunk every day for a long time.
Based on the assessment, the annual increased incidence of liver cancer by the intake of aflatoxin B1 in Pu'er tea was 0.027/100,000 people. According to a population of 1.37 billion, 370 cases of liver cancer patients were added each year due to drinking Pu'er tea.
If compared with the new incidence of liver cancer in China is from 26 to 28 people per 100,000 in 2013. About 356,200 new cases of liver cancer will appear in the country every year, and it is clear that the risk of liver cancer caused by Pu'er tea contamination of aflatoxin is almost negligible.
"It is Obviously that people will not drink Pu'er tea polluted by aflatoxin every day. 370 cases of liver cancer caused by polluted Pu'er tea is only a theoretical figure, said Chen Junshi.
Chen Junshi stressed that Pu'er tea may be contaminated with aflatoxin, but we can not say that Pu'er tea can't be drunk. The food mentioned above like bacon, roast duck and wine may be contaminated. Can't bacon and roast ducks be eaten? Can't wine be drunk? The answer is not. If we cancel a class of food with a little risk, and we ultimately have no food to eat.
On the other hand, except for the aflatoxin detected in Pu'er tea and the probability of detection, consumers are concerned about the quality and safety of Pu'er tea, and the market may indeed have some inferior and polluted Pu'er tea in circulation. Therefore, experts like Chen Junshi also suggested that the relevant departments should strengthen supervision to prevent the deterioration of Pu'er tea from entering the food field. For example, whether tea in bulk will become the raw material of making milk tea needs to be prevented.
Needless to say, the primary responsibility for food safety lies in business. The enterprises in producing Pu'er tea should pay more attention to the health problems in production, transportation, and storage, should prevent the products from being contaminated by mycotoxins and strive to minimize the pollution in Pu'er tea.