Evaluation of matcha tea quality index using portable NIR spectroscopy coupled with chemometric algorithms

Abstract

BACKGROUND The study reports a portable near infrared (NIR) spectroscopy system coupled with chemometric algorithms for prediction of tea polyphenols and amino acids in order to index matcha tea quality. RESULTS Spectral data were preprocessed by standard normal variate (SNV), mean center (MC) and first‐order derivative (1stD) tests. The data were then subjected to full spectral partial least squares (PLS) and four variable selection algorithms, such as random frog partial least square (RF‐PLS), synergy interval partial least square (Si‐PLS), genetic algorithm‐partial least square (GA‐PLS) and competitive adaptive reweighted sampling partial least square (CARS‐PLS). RF‐PLS was established and identified as the optimum model based on the values of the correlation coefficients of prediction (RP), root mean square error of prediction (RMSEP) and residual predictive deviation (RPD), which were 0.8625, 0.82% and 2.13, and 0.9662, 0.14% and 3.83, respectively, for tea polyphenols and amino acids. The content range of tea polyphenols and amino acids in matcha tea samples was 8.51–14.58% and 2.10–3.75%, respectively. The quality of matcha tea was successfully classified with an accuracy rate of 83.33% as qualified, unqualified and excellent grade. CONCLUSION The proposed method can be used as a rapid, accurate and non‐destructive platform to classify various matcha tea samples based on the ratio of tea polyphenols to amino acids. © 2019 Society of Chemical Industry

Simultaneous sex and species classification of silkworm pupae by NIR spectroscopy combined with chemometric analysis

“…The CARS method is mainly applied to eliminate useless or irrelevant spectral variables with the aim of establishing the classification model with high performance 23 . Its principle is the survival of the fittest of Evolution Theory.…”

“…20,21,22 Adaptive reweighted sampling The CARS method is mainly applied to eliminate useless or irrelevant spectral variables with the aim of establishing the classification model with high performance. 23 Its principle is the survival of the fittest of Evolution Theory. In CARS, the importance of each variable is determined by calculating the absolute values of regression coefficients of PLSR.…”

Principles and Applications of Miniaturized Near‐Infrared (NIR) Spectrometers

“…Table 2 summarizes current progress being made in this direction. An overview of current progress in food analytical applications of miniaturized NIR spectrometers reveals that, while compact devices can be successfully adopted for numerous types of analyses, the applicability potential and relative performance between devices largely varies [126–137] . The instrumental differences seem to be particularly evident in such applications, for example, highly affordable SW‐NIR spectrometers may yield good performance in analyzing some macronutrients, yet their applicability is largely limited in other scenarios.…”

Historical Evolution and Food Control Achievements of Near Infrared Spectroscopy, Electronic Nose, and Electronic Tongue—Critical Overview

“…Matcha tea, another trending product, was also analyzed with portable NIR instruments and satisfactory results were obtained for the estimation of the polyphenol and amino acid content of the tea samples after choosing the most accurate pretreatment methods. The best results consisted of R 2 of 0.86 for the prediction of polyphenols and 0.96 for the determination of amino acids [ 78 ].…”