Determination of Water Content in Oolong Tea and Green Tea by Near Infrared Spectrophotometric Analysis

Abstract

Near Infrared Spectrophotometer was examined to determine the water content in Oolong-tea and Green-tea, The second derivative NIR spectra of Olong-tea was nearly same as the result found in Greentea, and it showed a strong absorption at 1916 nm assigned to H₂O. Caribration curve of water content in Oolong-tea and Green-tea was made up of adsorbance values and used samples data by the method of loss on drying samples in atomospheric pressure. The water content of unknown tea samples was determined by NIR method with uses of these caribration curve. And these data were compared with the measure by drying method. As a result, with the uses of same kind of tea's caribration curve, the NIR method could compete in terms of accuracy with drying method. But, with the uses of different kind of tea's one, the errors were large.