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.

© 2012 Optical Society of America

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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
  7. P. O. Owuor and M. Obanda, “Comparative responses in plain black tea quality parameters of different tea clones to fermentation temperature and duration,” Food Chem. 72, 319–327 (2001).
    [CrossRef]
  8. Y. R. Liang, J. L. Lu, L. Y. Zhang, S. Wu, and Y. Wu, “Estimation of black tea quality by analysis of chemical composition and colour difference of tea infusions,” Food Chem. 80, 283–290 (2003).
    [CrossRef]
  9. Q. S. Cheng, S. Q. Jiang, and X. Y. Wang, “Discrimination of tea’s quality level based on electronic tongue and pattern recognition,” Food Machinery 24, 124–126 (2008).
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  11. X. H. Gu, Y. Feng, and J. Tang, “Discrimination of tea varieties by mid-infrared spectroscopy combined with PLS,” J. Anal. Sci. 24, 131–135 (2008).
  12. Z. Y. Niu, M. Y. Liu, and X. Lin, “Application of different near-infrared spectrometers in tea quality inspection,” Hubei Agric. Sci. 48, 2562–2565 (2009).
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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
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2010 (1)

P. O. Owuor, N. W. Francis, and K. N. Wilson, “Influence of region of production on relative clonal plain tea quality parameters in Kenya,” Food Chem. 119, 1168–1174(2010).
[CrossRef]

2009 (2)

X. L. Li and Y. He, “Classification of tea grade by multi-spectral images and combined features,” Trans. Chin. Soc. Agric. Machinery 40, 113–118 (2009).

Z. Y. Niu, M. Y. Liu, and X. Lin, “Application of different near-infrared spectrometers in tea quality inspection,” Hubei Agric. Sci. 48, 2562–2565 (2009).

2008 (3)

Q. S. Cheng, S. Q. Jiang, and X. Y. Wang, “Discrimination of tea’s quality level based on electronic tongue and pattern recognition,” Food Machinery 24, 124–126 (2008).

J. Zhou, H. Cheng, and L. Y. Wang, “Recent advance on the application of near-infrared spectroscopy in tea,” J. Tea Sci. 28, 294–300 (2008).

X. H. Gu, Y. Feng, and J. Tang, “Discrimination of tea varieties by mid-infrared spectroscopy combined with PLS,” J. Anal. Sci. 24, 131–135 (2008).

2006 (1)

J. P. Wold, R. Bro, A. Veberg, F. Lundby, A. N. Nilsen, and J. Moan, “Active photosensitizers in butter detected by fluorescence spectroscopy and multivariate curve resolution,” J. Agric. Food Chem. 54, 10197–10204 (2006).
[CrossRef]

2005 (1)

S. H. Yan, “Evaluation of the composition and sensory properties of tea using near infrared spectroscopy and principal component analysis,” J. Near Infrared Spectrosc. 13, 313–325 (2005).
[CrossRef]

2003 (2)

Y. R. Liang, J. L. Lu, L. Y. Zhang, S. Wu, and Y. Wu, “Estimation of black tea quality by analysis of chemical composition and colour difference of tea infusions,” Food Chem. 80, 283–290 (2003).
[CrossRef]

M. S. Kim, A. M. Lefcourt, and Y. R. Chen, “Multispectral laser-induced fluorescence imaging system for large biological samples,” Appl. Opt. 42, 3927–3934 (2003).
[CrossRef]

2001 (2)

M. S. Kim, J. E. McMurtrey, C. L. Mulchi, C. S. T. Daughtry, E. W. Chappelle, and Y. R. Chen, “Steady-state multispectral fluorescence imaging system for plant leaves,” Appl. Opt. 40, 157–166 (2001).
[CrossRef]

P. O. Owuor and M. Obanda, “Comparative responses in plain black tea quality parameters of different tea clones to fermentation temperature and duration,” Food Chem. 72, 319–327 (2001).
[CrossRef]

1998 (2)

P. O. Owuor and M. Obanda, “The effects of blending clonal leaf on black tea quality,” Food Chem. 66, 147–152(1998).
[CrossRef]

V. Raimondi, G. Cecchi, L. Pantani, and R. Chiari, “Fluorescence lidar monitoring of historic buildings,” Appl. Opt. 37, 1089–1098 (1998).
[CrossRef]

1997 (2)

D. A. Balentine, S. A. Wiseman, and L. C. Bouwens, “The chemistry of tea flavonoids,” Crit. Rev. Food Sci. Nutr. 37, 693–704 (1997).

A. J. Hoff and J. Deisenhofer, “Photophysics of photosynthesis. Structure and spectroscopy of reaction centers of purple bacteria,” Phys. Rep. 287, 1–247 (1997).
[CrossRef]

1995 (1)

S. Svanberg, “Fluorescence lidar monitoring of vegetation status,” Phys. Scr. T 58, 79–85 (1995).

1991 (1)

M. Lang, F. Stober, and H. K. Lichtenthaler, “Fluorescence emission-spectra of plant-leaves and plant constituents,” Radiat. Environ. Biophys. 30, 333–347 (1991).

1990 (1)

S. Andersson-Engels, J. Johansson, U. Stenram, K. Svanberg, and S. Svanberg, “Time-resolved laser-induced fluorescence spectroscopy for enhanced demarcation of human atherosclerotic plaques,” J. Photochem. Photobiol. B 4, 363–369 (1990).

1988 (1)

H. K. Lichtenthaler and U. Rinderle, “The role of chlorophyll fluorescence in the detection of stress conditions in plants,” CRC Crit. Rev. Anal. Chem. 19, S29–S85 (1988).
[CrossRef]

1985 (1)

1984 (2)

1982 (1)

H. F. Stich, M. P. Rosin, and L. Bryson, “Inhibition of mutagenicity of a model nitrosation reaction by naturally occurring phenolics, coffee and tea,” Mutation Res. 95, 119–128 (1982).
[CrossRef]

1975 (1)

G. V. Stagg and D. J. Millin, “The nutritional and therapeutic value of tea: a review,” J. Sci. Food Agric. 26, 1439–1459 (1975).
[CrossRef]

Andersson-Engels, S.

S. Andersson-Engels, J. Johansson, U. Stenram, K. Svanberg, and S. Svanberg, “Time-resolved laser-induced fluorescence spectroscopy for enhanced demarcation of human atherosclerotic plaques,” J. Photochem. Photobiol. B 4, 363–369 (1990).

Balentine, D. A.

D. A. Balentine, S. A. Wiseman, and L. C. Bouwens, “The chemistry of tea flavonoids,” Crit. Rev. Food Sci. Nutr. 37, 693–704 (1997).

H. N. Graham, M. E. Harbowy, and D. A. Balentine, “Tea: the plant and its manufacture; chemistry and consumption of the beverage,” in Caffiene, G. A. Spiller, ed. (CRC Press, 1998), pp. 65–66.

Bouwens, L. C.

D. A. Balentine, S. A. Wiseman, and L. C. Bouwens, “The chemistry of tea flavonoids,” Crit. Rev. Food Sci. Nutr. 37, 693–704 (1997).

Brian, W. P.

M. A. Mycek and W. P. Brian, Handbook of Biomedical Fluorescence, 1st ed. (CRC Press, 2003).

Bro, R.

J. P. Wold, R. Bro, A. Veberg, F. Lundby, A. N. Nilsen, and J. Moan, “Active photosensitizers in butter detected by fluorescence spectroscopy and multivariate curve resolution,” J. Agric. Food Chem. 54, 10197–10204 (2006).
[CrossRef]

Bryson, L.

H. F. Stich, M. P. Rosin, and L. Bryson, “Inhibition of mutagenicity of a model nitrosation reaction by naturally occurring phenolics, coffee and tea,” Mutation Res. 95, 119–128 (1982).
[CrossRef]

Cecchi, G.

Chappelle, E. W.

Chen, Y. R.

Cheng, H.

J. Zhou, H. Cheng, and L. Y. Wang, “Recent advance on the application of near-infrared spectroscopy in tea,” J. Tea Sci. 28, 294–300 (2008).

Cheng, Q. S.

Q. S. Cheng, S. Q. Jiang, and X. Y. Wang, “Discrimination of tea’s quality level based on electronic tongue and pattern recognition,” Food Machinery 24, 124–126 (2008).

Chiari, R.

Daughtry, C. S. T.

Deisenhofer, J.

A. J. Hoff and J. Deisenhofer, “Photophysics of photosynthesis. Structure and spectroscopy of reaction centers of purple bacteria,” Phys. Rep. 287, 1–247 (1997).
[CrossRef]

Feng, Y.

X. H. Gu, Y. Feng, and J. Tang, “Discrimination of tea varieties by mid-infrared spectroscopy combined with PLS,” J. Anal. Sci. 24, 131–135 (2008).

Francis, N. W.

P. O. Owuor, N. W. Francis, and K. N. Wilson, “Influence of region of production on relative clonal plain tea quality parameters in Kenya,” Food Chem. 119, 1168–1174(2010).
[CrossRef]

Graham, H. N.

H. N. Graham, M. E. Harbowy, and D. A. Balentine, “Tea: the plant and its manufacture; chemistry and consumption of the beverage,” in Caffiene, G. A. Spiller, ed. (CRC Press, 1998), pp. 65–66.

Gu, X. H.

X. H. Gu, Y. Feng, and J. Tang, “Discrimination of tea varieties by mid-infrared spectroscopy combined with PLS,” J. Anal. Sci. 24, 131–135 (2008).

Harbowy, M. E.

H. N. Graham, M. E. Harbowy, and D. A. Balentine, “Tea: the plant and its manufacture; chemistry and consumption of the beverage,” in Caffiene, G. A. Spiller, ed. (CRC Press, 1998), pp. 65–66.

He, Y.

X. L. Li and Y. He, “Classification of tea grade by multi-spectral images and combined features,” Trans. Chin. Soc. Agric. Machinery 40, 113–118 (2009).

Hoff, A. J.

A. J. Hoff and J. Deisenhofer, “Photophysics of photosynthesis. Structure and spectroscopy of reaction centers of purple bacteria,” Phys. Rep. 287, 1–247 (1997).
[CrossRef]

Jiang, S. Q.

Q. S. Cheng, S. Q. Jiang, and X. Y. Wang, “Discrimination of tea’s quality level based on electronic tongue and pattern recognition,” Food Machinery 24, 124–126 (2008).

Johansson, J.

S. Andersson-Engels, J. Johansson, U. Stenram, K. Svanberg, and S. Svanberg, “Time-resolved laser-induced fluorescence spectroscopy for enhanced demarcation of human atherosclerotic plaques,” J. Photochem. Photobiol. B 4, 363–369 (1990).

Jolliffe, I. T.

I. T. Jolliffe, “Choosing a subset of principal components or variables,” in Principal Component Analysis, 2nd ed. (Springer, 2002), pp. 115–118.

Kim, M. S.

Lakowicz, J. R.

J. R. Lakowicz, “Multiphoton excitation and microscopy,” in Principles of Fluorescence Spectroscopy, 3rd ed. (Springer, 2006), pp. 607–621.

Lang, M.

M. Lang, F. Stober, and H. K. Lichtenthaler, “Fluorescence emission-spectra of plant-leaves and plant constituents,” Radiat. Environ. Biophys. 30, 333–347 (1991).

Lefcourt, A. M.

Li, X. L.

X. L. Li and Y. He, “Classification of tea grade by multi-spectral images and combined features,” Trans. Chin. Soc. Agric. Machinery 40, 113–118 (2009).

Liang, Y. R.

Y. R. Liang, J. L. Lu, L. Y. Zhang, S. Wu, and Y. Wu, “Estimation of black tea quality by analysis of chemical composition and colour difference of tea infusions,” Food Chem. 80, 283–290 (2003).
[CrossRef]

Lichtenthaler, H. K.

M. Lang, F. Stober, and H. K. Lichtenthaler, “Fluorescence emission-spectra of plant-leaves and plant constituents,” Radiat. Environ. Biophys. 30, 333–347 (1991).

H. K. Lichtenthaler and U. Rinderle, “The role of chlorophyll fluorescence in the detection of stress conditions in plants,” CRC Crit. Rev. Anal. Chem. 19, S29–S85 (1988).
[CrossRef]

Lin, X.

Z. Y. Niu, M. Y. Liu, and X. Lin, “Application of different near-infrared spectrometers in tea quality inspection,” Hubei Agric. Sci. 48, 2562–2565 (2009).

Liu, M. Y.

Z. Y. Niu, M. Y. Liu, and X. Lin, “Application of different near-infrared spectrometers in tea quality inspection,” Hubei Agric. Sci. 48, 2562–2565 (2009).

Lu, J. L.

Y. R. Liang, J. L. Lu, L. Y. Zhang, S. Wu, and Y. Wu, “Estimation of black tea quality by analysis of chemical composition and colour difference of tea infusions,” Food Chem. 80, 283–290 (2003).
[CrossRef]

Lu, Y.

Y. Lu, The Classic of Tea: Origins & Rituals, Translated by F. R. Carpenter, ed. (Ecco Press, 1995).

Lundby, F.

J. P. Wold, R. Bro, A. Veberg, F. Lundby, A. N. Nilsen, and J. Moan, “Active photosensitizers in butter detected by fluorescence spectroscopy and multivariate curve resolution,” J. Agric. Food Chem. 54, 10197–10204 (2006).
[CrossRef]

McMurtrey, J. E.

Millin, D. J.

G. V. Stagg and D. J. Millin, “The nutritional and therapeutic value of tea: a review,” J. Sci. Food Agric. 26, 1439–1459 (1975).
[CrossRef]

Moan, J.

J. P. Wold, R. Bro, A. Veberg, F. Lundby, A. N. Nilsen, and J. Moan, “Active photosensitizers in butter detected by fluorescence spectroscopy and multivariate curve resolution,” J. Agric. Food Chem. 54, 10197–10204 (2006).
[CrossRef]

Montán, S.

Mulchi, C. L.

Mycek, M. A.

M. A. Mycek and W. P. Brian, Handbook of Biomedical Fluorescence, 1st ed. (CRC Press, 2003).

Newcomb, W. W.

Nilsen, A. N.

J. P. Wold, R. Bro, A. Veberg, F. Lundby, A. N. Nilsen, and J. Moan, “Active photosensitizers in butter detected by fluorescence spectroscopy and multivariate curve resolution,” J. Agric. Food Chem. 54, 10197–10204 (2006).
[CrossRef]

Niu, Z. Y.

Z. Y. Niu, M. Y. Liu, and X. Lin, “Application of different near-infrared spectrometers in tea quality inspection,” Hubei Agric. Sci. 48, 2562–2565 (2009).

Obanda, M.

P. O. Owuor and M. Obanda, “Comparative responses in plain black tea quality parameters of different tea clones to fermentation temperature and duration,” Food Chem. 72, 319–327 (2001).
[CrossRef]

P. O. Owuor and M. Obanda, “The effects of blending clonal leaf on black tea quality,” Food Chem. 66, 147–152(1998).
[CrossRef]

Owuor, P. O.

P. O. Owuor, N. W. Francis, and K. N. Wilson, “Influence of region of production on relative clonal plain tea quality parameters in Kenya,” Food Chem. 119, 1168–1174(2010).
[CrossRef]

P. O. Owuor and M. Obanda, “Comparative responses in plain black tea quality parameters of different tea clones to fermentation temperature and duration,” Food Chem. 72, 319–327 (2001).
[CrossRef]

P. O. Owuor and M. Obanda, “The effects of blending clonal leaf on black tea quality,” Food Chem. 66, 147–152(1998).
[CrossRef]

Pantani, L.

Raimondi, V.

Rinderle, U.

H. K. Lichtenthaler and U. Rinderle, “The role of chlorophyll fluorescence in the detection of stress conditions in plants,” CRC Crit. Rev. Anal. Chem. 19, S29–S85 (1988).
[CrossRef]

Rosin, M. P.

H. F. Stich, M. P. Rosin, and L. Bryson, “Inhibition of mutagenicity of a model nitrosation reaction by naturally occurring phenolics, coffee and tea,” Mutation Res. 95, 119–128 (1982).
[CrossRef]

Stagg, G. V.

G. V. Stagg and D. J. Millin, “The nutritional and therapeutic value of tea: a review,” J. Sci. Food Agric. 26, 1439–1459 (1975).
[CrossRef]

Stenram, U.

S. Andersson-Engels, J. Johansson, U. Stenram, K. Svanberg, and S. Svanberg, “Time-resolved laser-induced fluorescence spectroscopy for enhanced demarcation of human atherosclerotic plaques,” J. Photochem. Photobiol. B 4, 363–369 (1990).

Stich, H. F.

H. F. Stich, M. P. Rosin, and L. Bryson, “Inhibition of mutagenicity of a model nitrosation reaction by naturally occurring phenolics, coffee and tea,” Mutation Res. 95, 119–128 (1982).
[CrossRef]

Stober, F.

M. Lang, F. Stober, and H. K. Lichtenthaler, “Fluorescence emission-spectra of plant-leaves and plant constituents,” Radiat. Environ. Biophys. 30, 333–347 (1991).

Svanberg, K.

S. Andersson-Engels, J. Johansson, U. Stenram, K. Svanberg, and S. Svanberg, “Time-resolved laser-induced fluorescence spectroscopy for enhanced demarcation of human atherosclerotic plaques,” J. Photochem. Photobiol. B 4, 363–369 (1990).

S. Montán, K. Svanberg, and S. Svanberg, “Multicolor imaging and contrast enhancement in cancer-tumor localization using laser-induced fluorescence in hematoporphyrin-derivative-bearing tissue,” Opt. Lett. 10, 56–58 (1985).
[CrossRef]

Svanberg, S.

S. Svanberg, “Fluorescence lidar monitoring of vegetation status,” Phys. Scr. T 58, 79–85 (1995).

S. Andersson-Engels, J. Johansson, U. Stenram, K. Svanberg, and S. Svanberg, “Time-resolved laser-induced fluorescence spectroscopy for enhanced demarcation of human atherosclerotic plaques,” J. Photochem. Photobiol. B 4, 363–369 (1990).

S. Montán, K. Svanberg, and S. Svanberg, “Multicolor imaging and contrast enhancement in cancer-tumor localization using laser-induced fluorescence in hematoporphyrin-derivative-bearing tissue,” Opt. Lett. 10, 56–58 (1985).
[CrossRef]

S. Svanberg, “Fluorescence spectroscopy and imaging of lidar targets,” in Laser Remote Sensing, T. Fujii and T. Fukuchi, eds. (CRC Press, 2005), pp. 433–467.

Tang, J.

X. H. Gu, Y. Feng, and J. Tang, “Discrimination of tea varieties by mid-infrared spectroscopy combined with PLS,” J. Anal. Sci. 24, 131–135 (2008).

Veberg, A.

J. P. Wold, R. Bro, A. Veberg, F. Lundby, A. N. Nilsen, and J. Moan, “Active photosensitizers in butter detected by fluorescence spectroscopy and multivariate curve resolution,” J. Agric. Food Chem. 54, 10197–10204 (2006).
[CrossRef]

Wang, L. Y.

J. Zhou, H. Cheng, and L. Y. Wang, “Recent advance on the application of near-infrared spectroscopy in tea,” J. Tea Sci. 28, 294–300 (2008).

Wang, X. Y.

Q. S. Cheng, S. Q. Jiang, and X. Y. Wang, “Discrimination of tea’s quality level based on electronic tongue and pattern recognition,” Food Machinery 24, 124–126 (2008).

Wilson, K. N.

P. O. Owuor, N. W. Francis, and K. N. Wilson, “Influence of region of production on relative clonal plain tea quality parameters in Kenya,” Food Chem. 119, 1168–1174(2010).
[CrossRef]

Wiseman, S. A.

D. A. Balentine, S. A. Wiseman, and L. C. Bouwens, “The chemistry of tea flavonoids,” Crit. Rev. Food Sci. Nutr. 37, 693–704 (1997).

Wold, J. P.

J. P. Wold, R. Bro, A. Veberg, F. Lundby, A. N. Nilsen, and J. Moan, “Active photosensitizers in butter detected by fluorescence spectroscopy and multivariate curve resolution,” J. Agric. Food Chem. 54, 10197–10204 (2006).
[CrossRef]

Wood, F. M.

Wu, S.

Y. R. Liang, J. L. Lu, L. Y. Zhang, S. Wu, and Y. Wu, “Estimation of black tea quality by analysis of chemical composition and colour difference of tea infusions,” Food Chem. 80, 283–290 (2003).
[CrossRef]

Wu, Y.

Y. R. Liang, J. L. Lu, L. Y. Zhang, S. Wu, and Y. Wu, “Estimation of black tea quality by analysis of chemical composition and colour difference of tea infusions,” Food Chem. 80, 283–290 (2003).
[CrossRef]

Yan, S. H.

S. H. Yan, “Evaluation of the composition and sensory properties of tea using near infrared spectroscopy and principal component analysis,” J. Near Infrared Spectrosc. 13, 313–325 (2005).
[CrossRef]

Zhang, L. Y.

Y. R. Liang, J. L. Lu, L. Y. Zhang, S. Wu, and Y. Wu, “Estimation of black tea quality by analysis of chemical composition and colour difference of tea infusions,” Food Chem. 80, 283–290 (2003).
[CrossRef]

Zhou, J.

J. Zhou, H. Cheng, and L. Y. Wang, “Recent advance on the application of near-infrared spectroscopy in tea,” J. Tea Sci. 28, 294–300 (2008).

Appl. Opt. (5)

CRC Crit. Rev. Anal. Chem. (1)

H. K. Lichtenthaler and U. Rinderle, “The role of chlorophyll fluorescence in the detection of stress conditions in plants,” CRC Crit. Rev. Anal. Chem. 19, S29–S85 (1988).
[CrossRef]

Crit. Rev. Food Sci. Nutr. (1)

D. A. Balentine, S. A. Wiseman, and L. C. Bouwens, “The chemistry of tea flavonoids,” Crit. Rev. Food Sci. Nutr. 37, 693–704 (1997).

Food Chem. (4)

P. O. Owuor, N. W. Francis, and K. N. Wilson, “Influence of region of production on relative clonal plain tea quality parameters in Kenya,” Food Chem. 119, 1168–1174(2010).
[CrossRef]

P. O. Owuor and M. Obanda, “The effects of blending clonal leaf on black tea quality,” Food Chem. 66, 147–152(1998).
[CrossRef]

P. O. Owuor and M. Obanda, “Comparative responses in plain black tea quality parameters of different tea clones to fermentation temperature and duration,” Food Chem. 72, 319–327 (2001).
[CrossRef]

Y. R. Liang, J. L. Lu, L. Y. Zhang, S. Wu, and Y. Wu, “Estimation of black tea quality by analysis of chemical composition and colour difference of tea infusions,” Food Chem. 80, 283–290 (2003).
[CrossRef]

Food Machinery (1)

Q. S. Cheng, S. Q. Jiang, and X. Y. Wang, “Discrimination of tea’s quality level based on electronic tongue and pattern recognition,” Food Machinery 24, 124–126 (2008).

Hubei Agric. Sci. (1)

Z. Y. Niu, M. Y. Liu, and X. Lin, “Application of different near-infrared spectrometers in tea quality inspection,” Hubei Agric. Sci. 48, 2562–2565 (2009).

J. Agric. Food Chem. (1)

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Figures (13)

Fig. 1.
Fig. 1.

Laser-induced fluorescence setup, L38 (long pass filter at 380 nm). The tea samples were placed on a black metal sheet which was kept moving during each experiment.

Fig. 2.
Fig. 2.

Pictures of Guangdong (GD) teas: (a–e) correspond to Wudong Baiye Dancong (WBD), Dawuye (Autumn) (DA), Huangzhixiang Dancong (Spring) (HDS), Zhilanxiang Dancong (ZD), and Gongxiang Dancong (GD), respectively.

Fig. 3.
Fig. 3.

Pictures of north Fujian (N-FJ) oolong teas: (a–c) correspond to Shuixian (SX), Dahongpao (DHP), and Wuyi Rougui (superfine) (WRs), respectively.

Fig. 4.
Fig. 4.

Pictures of south Fujian (S-FJ) teas: (a–d) correspond to Baiya Qilan (BQ), Yongchun Foshou (YF), Huangdan (HD), and Tieguanyin (TGY), respectively.

Fig. 5.
Fig. 5.

Pictures of the Taiwan (TW) teas: (a–d) correspond to Wenshan Baozhong (WB), Dayuling (DYL), Dongding Oolong (DDO), and Alishan Tea (ALS), respectively.

Fig. 6.
Fig. 6.

Oolong tea fluorescence: (a–d) correspond to the spectra of GD, N-FJ, S-FJ, and TW tea samples, respectively. The peak around 355 nm is the elastic scattering of the excited wavelength. The fluorescence peak in the near infrared region is due to chlorophyll.

Fig. 7.
Fig. 7.

Eigenvalues of the principal components which represent the weight of each principal component. When data are projected on the first principal component, the signal to noise ratio, SNR, is as large as 10001.

Fig. 8.
Fig. 8.

Principal components: (a–i) correspond to the first through ninth components, respectively.

Fig. 9.
Fig. 9.

Predicted classifications for the oolong tea samples. The dotted lines are the mean predicted classification and the solid lines are the standard deviations corresponding to the mean predictive classification. Q14 is the discrimination index for each type of tea.

Fig. 10.
Fig. 10.

Jasmine tea pictures, (a–j) correspond to grade 1 to 10, respectively.

Fig. 11.
Fig. 11.

Fluorescence of jasmine teas. The fluorescence spectra have been averaged five times. The peak around 355 nm is the elastic scattering of the excited wavelength. The small peak around 710 nm is the second-order of the excitation wavelength. The weakness of this peak shows that the influence of the grating second-order spectrum in the 700–800 nm region is negligible. The fluorescence peak in the near infrared region is due to chlorophyll.

Fig. 12.
Fig. 12.

(a) Eigenvalues of the principal components, the first three eigenvalues represent most of the information; (b) the first three principal components.

Fig. 13.
Fig. 13.

Grade assessment of jasmine tea samples (where grade 1 means the best quality). The correlation coefficient between the predicted and expert grades is 0.986.

Tables (1)

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Table 1. Oolong Tea Names, Types, and Corresponding Abbreviations

Equations (8)

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S=U1N,1NΣ1N,1PV1P,1PT,
SU1N,1trΣ1tr,1trV1P,1trT.
Yk=1,2N,ki;1M=ϕk=1,2N,ki;0trθ0tr;1M,
ϕk,j={1j=0;Uk,jj=1,2tr;k=1,2N,ki.
Y^1M=ϕi;0trθ0tr;1M.
Yn,m={1ntypem0ntypemn=1,2N.
Qm=|μY^nmμY^nm|σY^nm2σY^nm2.
Ynt=nn=1,210,t=1,2,3,4,5,

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