Study suggests green tea extracts could reduce risk of infection with diarrhoea-causing norovirus
Scientists also found that green tea extract in combination with chitosan films can reduce levels of bacteria such as E coli and L innocua to undetectable levels after 24 hours of exposure
It’s not uncommon for one to get an upset stomach occasionally, particularly after eating outside food. This is often the result of different kinds of bacteria and viruses present in the food items. In a research, published in the International Journal of Food Science on 4 July 2020, scientists found that green tea extracts can help in reducing the risk of getting infected with a diarrhoea-causing virus known as norovirus.
What is norovirus?
Norovirus is a very contagious virus that leads to an infection that causes continuous vomiting and diarrhoea. It can affect both children and adults. Norovirus can spread by coming in direct contact with an infected person, by consuming contaminated food or water, or by touching contaminated surfaces and then putting the same unwashed hand in your mouth.
The green tea study
For this study, scientists from The Ohio State University prepared three different products to test the effectiveness of green tea extracts.
First, the scientists dissolved green tea extracts in chitosan film-forming solutions. Chitosan is a sugar that is collected from the hard outer skeleton of shellfish, including crab, lobster, and shrimp. A chitosan film-forming solution is prepared by dissolving 1.5 grams of chitosan powder in 100 millilitres of 1 percent acetic acid which is constantly stirred at 700 rpm (rotations per minute) at room temperature for six hours.
For the second one, they prepared dried chitosan edible films mixed with green tea extracts. The third product was green tea extract dissolved in de-ionised water, which acted as a control group.
All these products were exposed to norovirus, Escherichia coli (E. coli) and Listeria innocua.
The chitosan film-forming solution and de-ionised water were incubated in the norovirus solutions (which contained more than 1 million virus cells) for three hours while the dried chitosan edible films were exposed for 24 hours.
Effectiveness of edible chitosan films with green tea extracts
The results of the study showed that the chitosan film-forming solution which contained 2.5 percent and 5.0 percent rgreen tea extracts reduced the levels of norovirus by 2.5 and 4.0 logs, respectively, after 3 hours of exposure.
One log reduction means the viral load reduced by 10 times, whereas 2 log reduction means the viral load reduced by 100 times.
Similarly, the de-ionised water containing 1 percent, 1.5 percent, and 2.5 percent green tea extracts significantly reduced the levels of norovirus plaques by 1.7, 2.5, and 3.3 logs, respectively, after three hours of exposure.
The scientists found that after 24 hours of incubation, the dried chitosan edible films with 5 percent and 10 percent green tea extracts reduced 1.6 and 4.5 logs, respectively.
The most effective product was chitosan films with 15 percent green tea extracts as they reduced the levels of norovirus to an undetectable level after 24 hours of exposure.
The scientists further found that these chitosan green tea extract films can also reduce the levels of other foodborne illness-causing bacteria such as E coli and L innocua to undetectable levels after 24 hours of exposure.
The scientists concluded that these edible chitosan green tea extract films can be helpful in reducing the count of infectious viruses and bacteria such as norovirus and E coli within 24 hours. The combination of chitosan with green tea extract was considered the best as chitosan is reported to have antibacterial activities and can increase the effectiveness of green tea.
However, scientists believe that a lot of work is yet to be done before these green tea extract-infused films are ready for consumption. These films are to be made in such a manner that they would deliver the microbe-killing effect without changing the taste or smell of the food.
For more information, read our article on Green tea.
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