LAUSR

BACKGROUND The aim of this study is to monitor the antioxidant activity (AA) and total phenolic content (TPC) variations of different kinds of teas depending on the infusion temperature and time by using synchronous fluorescence spectroscopy (SFS) combined chemometrics as a rapid method. In this study, black tea, oolong tea, green tea, green tea powder (matcha) samples were brewed at 80°C and 96°C for 2.5 to 30 min. Synchronous fluorescence spectra were recorded at different wavelength interval (Δλ) values for optimal models. AA and TPC of tea samples were determined by 2,2-Diphenyl-1-picrylhydrazyl (DDPH) assay and Folin Ciocalteu methods as reference methods, respectively. Partial least square (PLS) method was used for correlation between reference methods and SFS method. RESULTS Results showed that SFS combined with chemometrics could be an alternative rapid way to TPC and AA activity of teas with 0.932 and 0.918 of validation R2 values in fermented teas (black tea-oolong) while with 0.961 and 0.860 of validation R2 values in non fermented teas (green tea and green tea powder), respectively. LOD and RMSEP values were ≤ 6.61 μg/mL and ≤ 17.42, respectively. CONCLUSION Based on the lowest R2 value (0.860) on TPC analysis, proposed method is more appropriate for AA analysis of green tea and green tea powder. Furthermore, infusion time was more effective for obtaining different amounts of TPC and AA in fermented tea types while only infusion temperature was effective on green tea and green tea powder samples. Therefore, obtained calibration-validation models gave better results for fermented tea types. This article is protected by copyright. All rights reserved.