Rongxiang Zhang

Effect of different storage years on the quality of unzymic and zymic Pu-er tea by FTIR combined with feature extraction

In this paper, Fourier Transform Infrared Spectroscopy (FTIR) combined with feature extraction was used to study unzymic and zymic Pu-er tea for different storage years, including 6 kinds of zymic tea and 2 kinds of unzymic tea. The result indicated that the absorption peaks of unzymic and zymic Pu-er tea had the tendency to decrease while the storage times prolonged. Compared to the tea for 1 year, the change of unzymic Pu-er is stronger than that of zymic Pu-er. Using the characteristic extraction process, projection offset of various kinds of tea on the projection score can be obtained. The projection offset of unzymic and zymic Pu-er were 10.0∼14.2 and 1.7∼4.3. The result showed that the former is far more than the latter. It is due to different proportion of chemical constituents exists in unzymic and zymic Pu-er tea, such as alkaloids and phenolic compunds. This study presents the certain scientific bases for investigating the effect of different storage years on the quality of unzymic and zymic Pu-er and storing efficiently.

Study on relative contents of principal components of different tea by infrared absorption spectroscopy

Fourier transform infrared absorption (FTIR) spectroscopy has been used to study the relative contents of principal components of different tea. Middle infrared(MIR) spectra in the range of 400∼4000 cm−1 has been obtained, which included six kinds of brand tea, corresponding remains and four kinds of component molecular. Contents of components in different kind of tea have been obtained by a new method that made spectral reconstruction based on five principal component model, particularly the remains of tea considered as primary components, as well as anthocyanic, theanine, epi-gallocatechin-3-gallaet and caffeine. All the correlation coefficient between original spectra of tea and reconstructive spectra are beyond 99% in the range of 800–2000 cm−1. Meanwhile, the fitting results clearly showed that the relative contents and regularity of theanine, epigallocatechin-3-gallae and caffeine were consistent with the reported results in different kind of tea. Therefore, it was confirmed that this new method can be used to identify tea samples effectively.

A Research of the Tea Trace Element by ICP Spectrograph

The content of trace element in the tea from the different producing area was measured by using the Inductively Coupled Plasma spectrum (ICP). The distributive rule of trace element and the relativity of different trace element content is studied. The results shows that: (1)the content of certain trace element (B、Cu、Fe、Zn、Mn, etc.) in the different producing area tea change obviously, but the content of K、Ca、Na remain stabilization. (2)The relative content between the different tea represent the linearity to B、Cu、Fe、Zn、Mn etc， furthermore the slope change with the changing of tea producing region. (3) There also exist the relativity between the slope change and the tea latitude change. The study have significance to analysis the character of tea producing region and protect the original producing region tea。

Clustering analysis for parted band based on infrared spectra of tea

The standard mid-infrared spectra of fifteen kinds of tea that respectively belongs to slight fermentation (green tea, yellow tea, white tea), moderate fermentation (oolong tea) and deep fermentation tea (black tea, dark tea) are measured by Fourier transform infrared spectroscopy. By the visual analysis on the spectra it is found that they are strongly similar, so it is difficult to distinguish the different spectra directly. The main characteristics of spectra are obtained by informatics method of feature extraction, and then the scientific method of clustering analysis for teas belong to different fermentation degree is found. In order to further improve the validity of clustering result and emphasize the contrast of character parts, the zonal analysis of multiband for the spectra is done. The results show that using feature extraction for spectra in the wavenumber range of 1800 to 800cm−1, the clustering effect is better than that in wavenumber ranges of 3700 to 2400cm−1, 3700 to 2400cm−1 plus 1800 to 800cm−1, 1300 to 600cm−1 and all wavenumber range of 4000 to 400cm−1. The above results indicate that the wavenumber range of 1800 to 800cm−1 is the primary spectral region of reflecting characteristic of tea, which doesnt drop the primary information of reflecting fermentation feature of tea, and almost doesnt include the interferential information of nonfermentation feature of tea.

A new method for identification of zymic Pu-er tea based on fourier transform infrared spectroscopy

In this paper, a new method, feature extraction algorithm, for identification of zymic Pu-er tea based on Fourier Transform Infrared (FTIR) spectroscopy is proposed. Infrared spectra of 19 kinds of tea (including 6 kinds of zymic Pu-er tea) are recorded using Fourier Infrared Spectrometer. Six typical kinds of tea (including 4 kinds of zymic Pu-er tea) are chosen to establish training set, and the others (including 2 kinds of zymic Pu-er tea) are left to establish predicting set, which is used to check the accuracy of the identification by projecting. As a result, Puer characteristic basis and a stable linear arbiter can be obtained after the training set is dealt with feature extraction, and also the projecting result shows a clear identification: the zymic Pu-er teas in the predicting set are located in the same side of the linear arbiter as that in training set, meanwhile the others in the other side, which indicates that the linear arbiter is capable to identify zymic Pu-er tea.

Influence of pretreating methods on the score result of principal component analysis of tea

The mid-infrared spectra of six typical kinds of tea are recorded with a Fourier transform infrared spectroscopy. With different pre-treating methods, including vector normalization, derivation and smoothing, the spectra are investigated in this work. By comparing with the principal component analysis score results from different pre-treating methods, it draws conclusions: (1) The result from no pre-treating method is poor, because most scores of samples are crossing; (2) The result from vector normalization is better than that with no pre-treating method, because different kinds of tea can be distinguished basically; (3) The result from first-order derivation and smoothing is much better than the second one, because the aggregation of same samples is improved; (4) The result from vector normalization plus first-order derivative and smoothing is the best, because it makes the best aggregation of same samples and the biggest degree of decentralization between different kinds of samples, and also completely eliminates the singular points. Therefore, based on principal component analysis of infrared spectra of tea, the last pre-treating method ensures that the six kinds of tea can be distinguished accurately and effectively.

The grade recognition of green tea

It is urgent to think up a quick and precise method for the identification of tea varieties and grades. The Fourier-transform infrared spectra of three grades of Xihu Longjing tea are measured, and in the spectra region of 400-4000 cm-1, which are build separately by the Savitzky-Golay smoothing and standard normal variate preprocessing method. It can be shown that the three different grades of Xihu Longjing have nearly the same characteristic peaks in conventional Fourier-transform infrared spectra. And the data analysis shows that the difference of correction coefficient in different grades is small. So only from the spectrum characteristic or correction coefficient the three grades of green tea can not be effectively recognized. The further analysis shows that the average derivation of the spectra can identify effectively and separate the different grades of tea quickly. Based on the analysis, a way of tea recognition which need not relate to the complicated component analysis of tea is given.

Singlet-Excitation Energy Transfer Among Carotenoids in the HL-LH2 Complex from Rhodopseudomonas Palustris

The structure of peripheral light harvesting complex (LH2) from photosynthetic bacterium Rhodopseudomonas(Rps.) palustris cultured at high-light(HL) is very complicated, which includes five kinds of carotenoids(Cars) molecules in one unit. Femtosecond time-resolved absorption spectroscopy has been used to study the process of excited-state energy transfer(EET) among Cars in LH2 excited by femtosecond laser pulse at different wavelength. The characteristic spectra of singlet (Sn) and triplet (T1) excitation Cars were observed in visible spectral region. The results suggest that the singlet EET processes may occur from Cars with shorter conjugation length(n) to that with longer conjugation length besides excitation energy internal conversion. These complicated excitation energy equilibrium in the HL-LH2 from Rps. palustris fulfills within 6 ps. It might imply that the coexistence of many Cars is helpful for Cars serving as photoprotection.