Development of a New Three-Dimensional Fluorescence Spectroscopy Method Coupling with Multilinear Pattern Recognition to
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Development of a New Three-Dimensional Fluorescence Spectroscopy Method Coupling with Multilinear Pattern Recognition to Discriminate the Variety and Grade of Green Tea Leqian Hu 1 & Chunling Yin 1
Received: 2 November 2016 / Accepted: 2 January 2017 # Springer Science+Business Media New York 2017
Abstract According to the different types and contents of amino acids in green tea, a new method was proposed for green tea classification and quality evaluation based on excitation-emission matrix (EEM) fluorescence spectroscopy coupled with multilinear pattern recognition in this work. Amino acids in green tea samples were first derived with formaldehyde and acetyl acetone solution. Derivatives of green teas were then scanned with a three-dimensional fluorescence spectrometry. Multilinear pattern recognition methods, including multilinear principal component analysis (M-PCA), self-weight alternative trilinear decomposition (SWATLD), and multilinear partial least squares discriminant analysis (N-PLS-DA) methods, were used to decompose the EEM data sets. All of these multilinear pattern recognition methods showed the clustering tendency for five different kinds of green tea. Compared with the other two methods, N-PLS-DA got more accurate and reliable classification result because it made full use of all the fluorescence information of the derivative green tea samples. At the same time, this method also revealed the possibility of evaluating the grade of green tea.
Keyword Green tea . Amino acid . Fluorescence derivative . Three-dimensional fluorescence spectrometry . Multidimensional pattern recognition methods
* Leqian Hu [email protected]
1
School of Chemistry and Chemical Engineering, Henan University of Technology, Zhengzhou 450001, China
Introduction Tea is a very important product because of its physiological properties and potential health benefits. It originated in China more than 2000 years ago. There are different tea varieties with different external qualities and inner qualities due to their production methods and chemical composition. Green tea, black tea, and Oolong tea are among the most popular categories across the world. Green tea is produced by panfrying or steaming the tea leaves. By contrast, in the processing of black tea, leaves are additionally fermented. If this fermentation is partially carried out, an intermediate kind of tea is obtained the Oolong tea (Alcäzar et al. 2007). The different tea categories possess different chemical and medical properties. Each product is unique on the basis of the nature, amount, and combination of the various components that give to tea a unique and individual organoleptic character. At the same time, fraud was an increasingly frequent phenomenon in food products. Fraud was a false modification of foods carried out by labeling lowquality products as the high-quality ones or marking the products’ origins with the false one instead of the true one. Being a natural food of a relatively high price, expensive tea has been mislabeled with inexpensive ones (includ
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