LED-induced fluorescence system for tea classification and quality assessment

•A fluorescence system, integrating several LEDs with different wavelengths, is constructed.•LED, instead of laser, was used for tea measurement and the choice of LED was discussed.•Classification of six types of tea beverages was studied to verify the ability of the system.•The system was employed in quality evaluation for tea leaves and corresponding liquid tea.

A fluorescence system was developed by using several light emitting diodes (LEDs) with different wavelengths as excitation light sources. The fluorescence sensor head consists of multi LED light sources and a multimode fiber for fluorescence collection, where the LEDs and the corresponding filters can be easily chosen to get appropriate excitation wavelengths for different applications. By analyzing fluorescence spectra with the principal component analysis method, the system was utilized in the classification of four types of green tea and two types of black tea beverages. Quality of Xihu Longjing tea leaves of different grades and that of the corresponding liquid tea samples were studied to further investigate the ability and application of the system in the evaluation of classification/quality of tea and other foods.