Discrimination of tea varieties based on FTIR spectroscopy and an adaptive improved possibilistic c‐means clustering

Abstract

As a green and healthy beverage, tea has been fascinated by the people

Variation in the Optical Properties of PEO-Based Composites via a Green Metal Complex: Macroscopic Measurements to Explain Microscopic Quantum Transport from the Valence Band to the Conduction Band

“…For a number of compounds, including carboxylic acids, esters, and alcohols, a sharp and strong peak lies at 1036 cm −1 ; identifying the stretching modes of C-O and the stretching vibration peaks around1236 cm −1 originates from the C-N vibrations in aliphatic amine groups [ 39 , 40 ]. The recorded FTIR spectra in the present study for BTLs is relatively analogous to those reported in the literature for green and black teas [ 33 , 36 , 41 , 42 , 43 , 44 , 45 ]. Both the bending and stretching vibrations in pyrimidine, imidazole, carbonyl, and methyl groups are in good accordance with the bands in the caffeine spectra that change between 1700 cm −1 and 400 cm −1 [ 46 , 47 , 48 ].…”

“…The functional groups of the BTL sample could be obtained by analyzing the spectral range between 400 and 4000 cm −1 , since it allows for the identification of the vibrational frequency of the chemical bonds that make up both inorganic and organic molecules. Absorption at functional groups occurs as a result of vibrations in a certain frequency band and exhibits a clear feature of IR absorption [ 33 ]. Figure 4 displays the FTIR spectra of BTL extracts.…”

Comprehensive applications of metabolomics on tea science and technology: Opportunities, hurdles, and perspectives

“…With the help of multivariate calibration methods such as partial least squares (PLS) algorithm, random frog (RF) crossed with PLS (RF‐PLS), and competitive adaptive reweighted sampling (CARS) crossed with PLS (CARS‐PLS), FT‐NIR has been widely applied in simultaneously quantifying the levels of catechins, caffeine, free amino acids, theaflavins, and moisture in tea leaves or final tea products (Chen et al., 2008; Chen, Zhao, Chaitep et al., 2009; Wang, Wang et al., 2018; Zareef et al., 2018). Besides, FT‐NIR and FT‐MIR coupled with pattern recognition methods can also be widely used to discriminate teas with different varieties and geographical origins, and even can be applied in identifying tea grades and tea processing degree, such as the fermentation degree of black teas (Chen et al., 2009; Esteki et al., 2022; Jin et al., 2020; Song et al., 2021; Zhou, Fu et al., 2020). Unlike MS based metabolomics, FT‐IR based metabolomics is more suitable for discriminant analysis of tea samples rather than searching for marker compounds due to the heavily overlapped peaks in the FT‐IR spectra of tea samples.…”

“…significantly increased after rocking process, and some of them escaped into the air (Hu et al., 2018; Liu et al., 2018). These volatiles are derived from phenylalanine, long‐chain fatty acids ( e.g ., α‐linolenic acid and linoleic acid), carotenoids, and glycosidically bound volatiles (GBVs), or from de novo synthesis (Hu et al., 2018; Zhou, Wu et al., 2020). However, many years of studies by Ziyin Yang's group have demonstrated that GBVs contributed less to forming free volatiles during the rocking process.…”

Multidimensional Surface-Enhanced Raman Scattering (SERS) Strategy for Tea Differentiation

“…Thus, there is a growing need for methods that can differentiate tea products. In fact, many analytical methods have been explored for tea discrimination, which include high-performance liquid chromatography (HPLC), , gas chromatography–mass spectrometry (GC–MS), inductively coupled plasma mass spectrometry (ICP-MS), colorimetric assay and fluorometric sensors, − Fourier transform infrared reflectance (FTIR) spectroscopy, , and nuclear magnetic resonance (NMR) spectroscopy . These techniques are reliable but tend to be time consuming.…”