Lead researcher Nabarun Bhattacharyya
Tea tasters may soon be robbed of their sniff jobs to certify the aroma of black tea. Researchers from Kolkata and Assam have developed an electronic nose1 with sensor-based technology that smells and declares when to stop fermentation black tea, a vital process in the production of quality black tea. The instrument could have immense application in the tea industry.

Of all the processing stages that tea leaves pass through, fermentation is vital to the production of quality black tea. During fermentation, tea leaves change colour from green to copper. The grassy smell transforms into floral. To know optimum fermentation time, the researchers developed the electronic nose — metallic oxide semiconductor sensors connected to computer supported data acquisition devices with odour handling and delivery system. The computer devices contained olfaction software including time-delay neural networks (TDNN) and self-organizing map (SOM) to classify aroma and predict optimum fermentation time.

During tea fermentation, air-blown odour vapour molecules come in contact with the sensors. This decreases the sensors' resistance compared to their original values, which are converted into voltage and fed into a computer via analogue to digital converter. A computed aroma profile is plotted on the screen while TDNN and SOM predict the optimum fermentation time.

"This study, for the first time, explores the application of sensor technology in testing tea aroma and shows good promise in quality control for tea industries," says lead researcher Nabarun Bhattacharyya, additional director of the Centre for Development of Advance Computing (C-DAC), Kolkata.