Aging Process of Puer Black Tea Studied by FTIR Spectroscopy Combined with Curve-Fitting Analysis
LI Dong-yu1, SHI You-ming1*, YI Shi-lai2
1. College of Physics and Electronic Engineering, Qujing Normal University, Qujing 655011, China 2. Citrus Research Institute, Southwest University-China Academy of Agricultural Sciences, Chongqing 400712, China
Abstract：For better determination of the chemical components in the Puer black tea, Fourier transform infrared spectroscopy was used for obtaining vibrational spectra of Puer black tea at different aging time. Fourier transform infrared (FTIR) spectra indicated that the chemical components had change in Puer black tea at different aging time. The leaf of Puer black tea was a complex system, its Fourier transform infrared spectrum showed a total overlap of each absorption spectrum of various components. Each band represented an overall overlap of some characteristic absorption peaks of functional groups in the Puer black tea. In order to explore the change of characteristic absorption peaks of functional groups with aging time, the prediction positions and the number of second peaks in the range of 1 900～900 cm-1 were determined by Fourier self-deconvolution at first, and later the curve fitting analysis was performed in this overlap band. At different aging time of Puer black tea, the wave number of second peaks of amide Ⅱ, tea polyphenol, pectin and polysaccharides at overlap band were assigned by curve fitting analysis. The second peak at 1 520 cm-1 was characteristic absorption band of amide Ⅱ, the second peaks of tea polyphenol and pectin appeared at 1 278 and 1 103 cm-1 respectively. Two second peaks at 1 063 and 1 037 cm-1, corresponds mainly to glucomannan and arabinan. The relative area of these second peaks could be indicated the content of protein, tea polyphenol, pectin and polysaccharides in the Puer black tea. The results of curve fitting analysis showed that the relative area of amide Ⅱ was increasing first and then decreasing, it indicated the change of protein in Puer black tea. At the same time, the content of tea polyphenol and pectin were decreased with the increase of aging time, but the glucomannan and arabinan were increased in reverse. It explained that the bitter taste was become weak and a sweet taste appeared in the tea with the increase of aging time. The present study suggested that Fourier transform infrared spectroscopy combined with curve-fitting analysis could reveal the biochemical changed of Puer black tea with the increase of aging time, and it was evidence for evaluation the quality of Puer black tea.
Key words：Fourier transform infrared spectroscopy;Curve-fitting analysis;Puer black tea;Aging process
李栋玉1，时有明1*，易时来2 . FTIR结合曲线拟合分析用于普洱熟茶陈化过程的研究 [J]. 光谱学与光谱分析, 2015, 35(07): 1860-1863.
LI Dong-yu1, SHI You-ming1*, YI Shi-lai2 . Aging Process of Puer Black Tea Studied by FTIR Spectroscopy Combined with Curve-Fitting Analysis . SPECTROSCOPY AND SPECTRAL ANALYSIS, 2015, 35(07): 1860-1863.
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