Abstract:Four varieties of tea were collected from different areas in China including jasmine tea, Kuding tea, Longjing tea and Tieguanyin. A total of 120 samples (30 samples for each variety) were prepared. The original samples spectra were obtained using NIRSystem6500 analyzer. Tea was analyzed qualitatively and quantitatively by near infrared spectroscopy technology. Principal component analysis and discriminant analysis were used to distinguish the four varieties of tea. The optimal calibration model for qualitative discrimination was established according to comparison of different spectral data pretreatment methods and the uncertain factor coefficients. Quantitative analysis models for moisture content, tea polyphenol and caffeine in tea were developed with modified partial least square. The results show that the accurate recognition rate for the four varieties of tea in the validation set reached 100%. The coefficients of determination (R2P) and relative prediction deviation (RPD) of independent validation sets were more than 0.91 and 3.0, respectively. It is concluded that NIRS can be used as a rapid method to detect the variety and chemical components in tea.
[1] LIU Jun-hai, LI Zhi-zhou(刘均海, 李志州). Food Research and Development(食品研究与开发), 2007, 28(3): 173. [2] XIE Li-juan, YING Yi-bin, YING Tie-jin, et al(谢丽娟,应义斌,应铁进,等). Spectroscopy and Spectral Analysis(光谱学与光谱分析), 2008, 28(5): 1062. [3] LIU Li-li, YUAN Yuan, CHEN Wan-sheng, et al(刘荔荔,原 源,陈万生,等). Chinese Traditional and Herbal Drugs(中草药), 2001, 32(11): 1024. [4] SUN Yao-guo, LIN Min, Lü Jin, et al(孙耀国, 林 敏, 吕 进, 等). Chinese Journal of Spectroscopy Laboratory(光谱实验室), 2004, 21(5): 940. [5] LIU Hui-jun, Lü Jin, ZHANG Wei-gang, et al(刘辉军, 吕 进, 张维刚, 等). Infrared Technology(红外技术), 2007, 29(7): 429. [6] Kerstin Michel, Christian Bruns, Thomas Terhoeven, et al. J. Near Infrared Spectroscopy, 2006, 14(4): 251. [7] LI Qiong-fei, YANG Zeng-ling, HAN Lu-jia(李琼飞, 杨增玲, 韩鲁佳). Journal of Infrared Millimeter Waves(红外与毫米波学报), 2007, 26(6): 414. [8] LIU Qing-sheng, FAN Zhi-ying, ZHANG Ping(刘庆生, 范志影, 张 萍). Modern Scientific Instruments(现代科学仪器), 2007, (1): 66. [9] LIN Xin, NIU Zhi-you(林 新,牛智有). Journal of Huazhong Agricultural University(华中农业大学学报), 2008, 27(2): 326. [10] Malley D F, Mcclure C, Martin P D. Communications in Soil Science & PlantAnalysis, 2005, 36(4): 455.