三类滇产茶的红外光谱解析及三级鉴定

为了建立一种滇产绿茶、红茶及普洱熟茶的红外光谱鉴定方法,通过采集三类茶的红外光谱及二维相关红外光谱并进行三级红外光谱(傅里叶变换红外光谱结合二阶导数红外光谱及二维相关红外光谱)解析.红外光谱对比分析表明:1 644、1 517、1 451、1 237及1 040 cm-1是三类茶的共有特征峰,它们的吸收强度从绿茶、红茶到普洱熟茶依次减弱;二阶导数谱中,三类茶间的吸收峰位置、强度差异更加明显;与草酸钙的二阶导数谱对比分析发现,三类茶的草酸钙相对含量为:绿茶<红茶<普洱熟茶.二维相关红外光谱显示了三类茶的最强自动峰分别为1 635、1 563及1 639 cm-1,通过三级红外光谱分析可实现三类滇产茶的鉴定.

Analysis and identification of three kinds of tea from Yunnan province by three-level infrared spectroscopy

For developing a method to identify green tea( GT),black tea( BT) and ripened Pu-erh tea( PET) from Yunnan province,Fourier transform infrared spectroscopy( FT-IR) and two-dimensional correlation infrared spectroscopy( 2D-IR) were used plus a three-level infrared spectroscopy method( FT-IR combined with second derivative infrared spectroscopy( SD-IR) and 2D-IR). The comparative analysis of FT-IR shows that 1 644,1 517,1 451,1 237 and 1 040 cm-1are common characteristic peaks of GT,BT and PET and the absorption intensity of them decreases in order. Accordingly,the three kinds of tea can be differentiated primarily. The differences of peak position and peak intensity among the three teas become more evident in SD-IR. By comparison with SD-IR of calcium oxalate,it can be found that the relative content of calcium oxalate in the three tea samples is as follows:GT < BT < PET. Subsequently,2D-IR spectra have displayed the differences among the three types tea in a visualized way. The strongest auto-peak in 2D-IR of GT,BT and PET is 1 635,1 563 and 1 639 cm-1respectively. The analysis results have demonstrated that GT,BT and PET have their own infrared spectral characteristics and can be identified unambiguously by the three-level infrared spectrum analysis.