On-site estimation of total polyphenol in fresh tea leaf using near-infrared spectroscopy

The quality of tea liquor primarily depends on the quality of inbound fresh leaves to a tea factory. We report here the development of an industrial set-up using diffuse reflectance near-infrared spectroscopy for quick and on-spot estimation of total polyphenol content, which is one of the major quality indicators of tea. In the inspection system, freshly plucked tea leaves are dried with a heating system designed in such a way that the moisture content is reduced to around 3–4%. The dried leaves are then ground and sieved through a 250 µm mesh. Samples thus produced are placed automatically before the near-infrared beam and assessment of total polyphenol is done instantaneously.