Darjeeling tea vs Nepal tea: Can a ‘chemical fingerprint’ stop mislabelling?

For Darjeeling tea, the trouble with Nepal began with a crisis of its own. In 2017, due to the prolonged unrest related to the Gorkhaland movement, the Darjeeling tea gardens shut for more than 100 days during the crucial harvesting period. Buyers had to go elsewhere. Nepal, with tea-growing areas sharing several climatic and elevation characteristics with the Darjeeling hills, emerged as a cheaper alternative. What began as a supply issue gradually became a serious commercial challenge for Darjeeling tea.

Since then, the tea industry has faced a difficult question: how does it protect the value of a tea whose name has been built over more than a century?

Science may offer part of the answer

Researchers at the Tea Research Association (TRA) have analysed authenticated tea samples from 45 Darjeeling gardens and around 30 tea gardens in Nepal, as part of a much larger study covering 325 tea gardens across eight different tea-growing regions. The study identified 397 volatile flavour compounds (VFCs) in the Darjeeling samples. These are the chemical components that contribute to the aroma and flavour of tea.

More importantly, the research has identified a group of compounds that could potentially help to distinguish Darjeeling tea from Nepal tea. The importance lies not merely in discovering more chemicals in tea, but in trying to establish a considerable identity for Darjeeling.

Darjeeling tea received its Geographical Indication (GI) registration in 2004, recognising the distinct characteristics associated with tea produced in its defined geographical region. But a GI establishes geographical origin; it does not by itself provide a detailed laboratory fingerprint capable of identifying every sample.

That is where the latest TRA research could become important. Dr Bappaditya Kanrar, researcher at TRA, explained during an interaction at the association's Kolkata office that the scientists collected samples from 325 gardens representing eight tea-growing regions. These included Darjeeling and other Indian tea-growing areas such as Dooars, Assam, Himachal Pradesh and southern India, besides Nepal, Sri Lanka and Africa.

Of the total sample base, while 45 gardens represented Darjeeling, around 30 gardens were from Nepal. The Darjeeling samples were authenticated and represented different seasons, elevations, gardens, clones and manufacturing practices.

“The idea was to understand how the flavour chemistry varies across these regions and, more specifically, what makes Darjeeling special,” Kanrar said.

Across the samples, the researchers identified about 4,800 unique volatile flavour compounds. Of these, 397 were found in Darjeeling tea.

The scale of the study is significant because the researchers were not trying to define Darjeeling through a single garden, clone or harvest. Instead, they examined tea produced under different geographical and manufacturing conditions to understand the broader chemical profile of the region.

The research found that around 25 to 30 volatile flavour compounds could be particularly useful in differentiating Darjeeling tea from the Nepal samples analysed. Some were detected in the Darjeeling samples but not in the Nepal samples studied. The researchers also found compounds occurring in Nepal tea that were not detected in the Darjeeling samples.

The distinction, Kanrar stressed, should not be interpreted as a quality judgement on Nepal tea. The scientific question is narrower: whether a chemical pattern can help determine if a sample conforms to a genuine Darjeeling profile.

For an industry that has repeatedly raised concerns about the mixing or substitution of cheaper tea, that could be significant.

Joydeep Phukan, secretary and principal officer of TRA, regards the research as the beginning of a more scientific definition of Darjeeling's identity.

“What this study has done is essentially a self-diagnosis of Darjeeling tea,” Phukan said. “We have profiled its volatile flavour compounds across different clones, gardens and elevations, and found that its flavour profile is much more multifaceted.”

The next challenge is to turn that knowledge into practical use. Phukan said the identified volatile compounds could eventually be incorporated into a near-infrared analytical system. Such a system could compare a tea sample with the established chemical profile of authenticated Darjeeling tea and flag samples that do not conform.

“The GI tag by itself is essentially a declaration on paper. What Darjeeling needs now is an analytical backdrop to that geographical indication,” Phukan said.

The latest research could therefore add a new layer to the existing GI and traceability mechanisms. Instead of relying only on geographical declarations and certification, the industry could eventually have a scientific reference profile against which suspicious samples could be tested.

But that stage is for the future to hold. The chemical markers identified in the current research will need further validation.

If the transition is achieved, Darjeeling tea could acquire something its GI protection has never fully provided. It could have a scientific fingerprint.

For an industry that is trying to recover the premium attached to its name, the ability to demonstrate, through chemistry, what makes Darjeeling tea different could become an important weapon not against Nepal tea, but against the mislabelling and substitution that threaten the value of its name.