Simultaneous and Rapid Measurement of Main Compositions in Black Tea Infusion Using a Developed Spectroscopy System Comb
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Simultaneous and Rapid Measurement of Main Compositions in Black Tea Infusion Using a Developed Spectroscopy System Combined with Multivariate Calibration Wenxiu Pan & Jiewen Zhao & Quansheng Chen & Dongliang Zhang
Received: 8 April 2014 / Accepted: 30 July 2014 / Published online: 9 August 2014 # Springer Science+Business Media New York 2014
Abstract This study assessed the feasibility on simultaneous and rapid measurement of total polyphenol and caffeine contents in black tea infusion using a developed spectroscopy system. First, a portable visible/near infrared (VIS-NIR) spectroscopy system was developed for data acquisition, and then synergy interval partial least squares (Si-PLS), backpropagation artificial neural network (BP-ANN), and adaptive boosting (AdaBoost) combined with BP-ANN, namely BP-AdaBoost, were used comparatively for modeling. The performances of these models were evaluated according to the correlation coefficient (Rp) in the prediction set. Experimental results showed that the performances of nonlinear BP-ANN and BP-AdaBoost models were superior to those of linear Si-PLS models. In particular, BP-AdaBoost models have made a great progress in contrast to BP-ANN models, with Rp =0.9382 for total polyphenol content and Rp =0.9471 for caffeine content. The overall results indicated that this developed spectroscopy system combined with a suitable multivariate calibration tool could be used for the simultaneous and rapid measurement of the main compositions in black tea infusion. Keywords Black tea infusion . Total polyphenols . Caffeine . Spectroscopy . Multivariate calibration
Introduction Tea is known to be one of the most popular beverages in the world with a long history, which has formed its own culture in W. Pan : J. Zhao : Q. Chen (*) : D. Zhang School of Food and Biological Engineering, Jiangsu University, 212013 Zhenjiang, China e-mail: [email protected]
a specific area. It is manufactured by a variety of processes producing a range of variants from green, nonfermented tea to black fermented tea. After tea leaves are plucked, a number of processing stages such as withering, rolling, fermentation, and drying are involved in producing finished black tea, among which, fermentation is a critical operation (Bhattacharyya et al. 2007). This process is a series of biochemical reactions concentrating on the enzymatic oxidation of tea polyphenols (Subramanian et al. 1999; Zhao et al. 2006), whereas caffeine is considered to have a stimulative effect, which can enhance observably tea flavor (Roberts 1963; Chen et al. 2006). Therefore, total polyphenol and caffeine contents are determined to be the main compositions in black tea infusion. With the increasing consumption of black tea, quality control of black tea becomes more and more important nowadays, for instance, numerous national and international authorities are setting criteria for quality attributes (Airy 1999). During the past few decades, various analytical methods had been employed to measure the contents of main quality compositions
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