Handheld Electronic Nose (HEN) for Detection of Optimum Fermentation Time during Tea Manufacture and Assessment of Tea Quality

Abstract

Fermentation is an important process in tea manufacturing cycle and proper fermentation of tea leaves determines the quality of made tea. Both over and under fermentation affects the quality of made tea. To understand the optimum fermentation time and flavour of the processed tea, CDAC Kolkata had developed a hand-held electronic nose system (HEN). The system consists of top, mid and bottom section. Top section contains major portion of electronics, display, pump, sensor array and battery. The detachable mid-section holds the valve and provides an air path between pump and sample holder and between sample holder and sensor array. The bottom section is a threaded glass jar that acts as the sample holder. The HEN can be handy in determining the optimum fermentation end point during manufacturing process and to assess the quality of processed tea based on its aroma. Fixed quantity (half of the sample holder) of sample was taken from fermentation bed at an interval of five minutes and the generated aroma volatiles were discharged to the sensor array. The captured aroma was plotted against time to get the second aroma peak, which determined the optimum end point of fermentation. This was compared with the existing chemical method. The results obtained through HEN were correlated with the existing chemical method. The processed teas consisting CTC and orthodox types of manufacture and different grades were evaluated through HEN and the results were compared with organoleptic evaluation of tea by national and international tea tasters. The results revealed that the Handheld Electronic Nose is a suitable instrument for determining the optimum fermentation time during tea manufacture based on aroma.