Scientists Reveal the Dirty Secret to a Better Cup of Tea

Could the secret to the perfect cup of tea be hiding underground?

The complex flavors in a quality cup of tea are often attributed to the plant’s leaves. But new research suggests that the taste of a quality cuppa may also depend on the plant’s roots—specifically, the microbes that live there.

Tea breeders in China have spent centuries cultivating the perfect cup of tea. But despite modern breeding technologies, improving the taste of tea through genetic selection alone has proven to be a challenge. But a new study, published in the journal Current Biology, has shown that DNA is not the only thing that affects the taste of tea.

“Significant disparities in microbial communities, particularly nitrogen metabolism-related microorganisms, were identified in the roots of tea plants with varying qualities through microbiomics,” co-author Tongda Xu, a researcher at the Fujian Agriculture and Forestry University in Fujian, China, said in a statement.

Previous studies have shown that these microbes can affect the plant’s ability to take up nutrients from the soil around them. And, it turns out, these nutrients can affect the plant’s production of certain chemicals that may affect their taste.

Specifically, the team found that plants with microbes that encourage the uptake of ammonia produce more of a compound called theanine, a key determinant of the tea’s taste.

Armed with this knowledge, the team created a synthetic microbial community, based on those found on high-theanine tea varieties. By applying these synthetic colonies to roots of other tea plants, the team found that they were able to boost theanine levels in low-theanine varieties too.

“The initial expectation for the synthetic microbial community derived from high-quality tea plant roots was to enhance the quality of low-quality tea plants,” co-author Wenxin Tang said in a statement. “However, to our astonishment, we discovered that the synthetic microbial community not only enhances the quality of low-quality tea plants but also exerts a significant promoting effect on certain high-quality tea varieties. Furthermore, this effect is particularly pronounced in low-nitrogen soil conditions.”

These findings suggest that synthetically produced microbial communities could be used to improve the taste of tea plants, particularly when their surrounding soils lack key plant nutrients. These colonies may also support nutrient uptake in other plant species, allowing farmers to rely less on synthetic fertilizers.

“Our study provides compelling evidence supporting the use of root microorganisms as functional microbial fertilizers to enhance tea quality,” the authors write.