Tea polyphenols (Tp) and free amino acids (Aa) are the most important quality materials in tea
drinks. Due to the high number of samples to be analyzed, new analytical techniques providing fast and
reliable data about the quality are essential. Therefore, a portable near-infrared spectroscopy (NIR)
analyzer was developed for real-time, continuous and quantitative determination of Tp and Aa in tea
drinks. The portable NIR tea drinks analyzer is composed of a lamphouse, a temperature-controlled
sample chamber, an optical fiber and an InGaAs array mini grating spectrometer. The analyzer is
compact, lightweight and robust with no movable elements. The software with the functions of
spectrum acquisition, model establishment, method selection and real-time analysis was also developed
for the analyzer. Using partial least squares (PLS) regression, the calibration models for the
quantification of Tp and Aa were established with reference to the GB methods (the national standard
methods). The values of root mean square error of cross validation (RMSECV) of the models for Tp
and Aa calibration were 0.059 mg/mL, 0.005 mg/mL, the values of the correlation coefficients (R2)
were 0.99 and 0.98 respectively. The relative standard deviation (RSD) of ten repetitive testing were
3.17% and 4.15%. It suggested that the portable NIR tea drinks analyzer could be a fast and reliable
alternative for tea drinks quality testing.
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