Rapid Discrimination of the Geographical Origins of an Oolong Tea (Anxi-Tieguanyin) by Near-Infrared Spectroscopy and Partial Least Squares Discriminant Analysis

Abstract

This paper focuses on a rapid and nondestructive way to discriminate the geographical origin of Anxi-Tieguanyin tea by near-infrared (NIR) spectroscopy and chemometrics. 450 representative samples were collected from Anxi County, the original producing area of Tieguanyin tea, and another 120 Tieguanyin samples with similar appearance were collected from unprotected producing areas in China. All these samples were measured by NIR. The Stahel-Donoho estimates (SDE) outlyingness diagnosis was used to remove the outliers. Partial least squares discriminant analysis (PLSDA) was performed to develop a classification model and predict the authenticity of unknown objects. To improve the sensitivity and specificity of classification, the raw data was preprocessed to reduce unwanted spectral variations by standard normal variate (SNV) transformation, taking second-order derivatives (D2) spectra, and smoothing. As the best model, the sensitivity and specificity reached 0.931 and 1.000 with SNV spectra. Combination of NIR spectrometry and statistical model selection can provide an effective and rapid method to discriminate the geographical producing area of Anxi-Tieguanyin.

The Quality Control of Tea by Near-Infrared Reflectance (NIR) Spectroscopy and Chemometrics

“…e same kind of tea from different geographical origins might vary dramatically in prices and quality [17]. erefore, almost all of the famous teas are labeled with their origins, such as Anji-white tea, Anxi-Tieguanyin tea, and Yingde-black tea [36,53]. However, some merchants fraudulently falsify the geographical origins of tea for illegal profits.…”

“…However, some merchants fraudulently falsify the geographical origins of tea for illegal profits. It is urgent to enforce quality control against various counterfeits [53]. NIR spectroscopy has been successfully used for determining the geographical origin of various teas in recent years.…”

“…e sensitivity and specificity of the PLSDA model based on SNV transformation reached 0.93 and 1.00, respectively. NIR spectrometry combined with the SNV-PLSDA model thus could discriminate the geographical origins of Tieguanyin tea rapidly [53]. Recently, the combinational analysis of NIR spectroscopy and proton nuclear magnetic resonance ( 1 H NMR) has been used for distinguishing 90 Tieguanyin tea samples, which were collected from three different growing places (Xiandu, Xianghua, and Xiping towns) in the Fujian Province of China.…”

Geographical origin identification and quality control of Chinese chrysanthemum flower teas using gas chromatography–mass spectrometry and olfactometry and electronic nose combined with principal component analysis

“…Identifying authentic flower teas is difficult when withered ornamental chrysanthemums are used in the processing of flower teas. Improper use of geographical origins damages the interests of consumers and harms the profits of tea producers (Huo et al, 2014;Yan et al, 2014). In addition, chrysanthemums are sulphur-fumigated during postharvesting handling and preservation to decrease the drying time, preserve colour and prevent insects and moulds (Ding et al, 2014;Chen et al, 2015).…”

Electronic Tongue Combined with Chemometrics to Provenance Discrimination for a Green Tea (Anji-White Tea)

“…This paper was focused on developing an instrumental technique for discriminating the provenance of Anji-White tea by electronic tongue system and chemometrics, to model the complicated relationship between the taste and the geographical origin; principal component analysis (PCA) and partial least squares discriminant analysis (PLSDA) models were used in classification [10][11][12][13].…”