Tea classification and quality assessment using laser-induced fluorescence and chemometric evaluation

Abstract

Laser-induced fluorescence was used to evaluate the classification and quality of Chinese oolong teas and jasmine teas. The fluorescence of four different types of Chinese oolong teas-Guangdong oolong, North Fujian oolong, South Fujian oolong, and Taiwan oolong was recorded and singular value decomposition was used to describe the autofluoresence of the tea samples. Linear discriminant analysis was used to train a predictive chemometric model and a leave-one-out methodology was used to classify the types and evaluate the quality of the tea samples. The predicted classification of the oolong teas and the grade of the jasmine teas were estimated using this method. The agreement between the grades evaluated by the tea experts and by the chemometric model shows the potential of this technique to be used for practical assessment of tea grades.

Laser-induced fluorescence monitoring of Chinese longjing tea

“…This is in contrast to the case of jasmine teas, which could be readily classified from their fluorescence signatures [16]. We suggest the use of multiple excitation wavelengths in further studies of tea quality.…”

“…This suggests that the tea quality of the Longjing tea has no obvious relationship with fluorescence spectra excited by 355 nm. By comparison with the fluorescence spectra of jasmine tea in [16], the fluorescence spectra of Longjing tea samples are quite similar to each other. On the other hand, it is obvious that the FRF/RF ratios for the dried tea samples are much lower than the ratios of the tea branches given in Fig.…”

“…In this work, we present the preliminary work on remote fluorescence monitoring of Longjing tea, which is one of the most famous green tea species in the world. Longjing tea varieties were also investigated in laboratory fluorescence measurements combining singular value decomposition (SVD) and linear discriminant analysis (LDA), which has previously been used to successfully identify the quality and type of Chinese jasmine and oolong teas in [16].…”

“…1. The remote measurement scheme as well as the laboratory systems used here have previously been described in [16,17]. A brief description of the system and the experimental scheme is also given here.…”

Grade Identification of Tieguanyin Tea Using Fluorescence Hyperspectra and Different Statistical Algorithms

“…Chlorophyll is a key pigment in the photosynthesis of tea leaves, and the fluorescent signal can reflect the content of chlorophyll. Chlorophyll has the dual‐peaked distribution in the near‐infrared region with peaks around 690 and 735 nm (Mei, Lundin, & Brydegaard, ). Differences in chlorophyll content between different samples can result in differences in fluorescent intensity.…”