Real-time monitoring of tea volatiles using soft ionization by chemical reaction in transfer with an online sampling interface

Abstract

Characterization of tea volatile substances is important for tea quality assessment, flavor evaluation, and manufacturing process control. In this work, an online monitoring system was developed and directly coupled with soft ionization by chemical reaction in transfer (SICRIT) ion source. Tea samples were roasted online at 160 °C, and the generated vapors were transferred to the SICRIT source for real-time ionization and high-resolution mass spectrometry (MS) detection. The results showed progressive release of numerous volatile compounds during the roasting process. Distinctive mass spectral profiles were observed at different time intervals, and teas with varying fermentation degrees exhibited different chemical fingerprints. The detected compounds included N-heterocyclics, esters, amines, alcohols, amino acids. Some are characteristic tea flavor compounds while others are Maillard reaction products. Multivariate data analysis clearly differentiated tea samples based on the acquired mass spectral data. With its miniaturized design and simple operation, SICRIT demonstrated excellent performance for direct analysis of odor compounds. The integrated SICRIT-MS system enabled direct, real-time analysis of volatile compounds through continuous vapor generation, transfer, and ionization, providing a simple and efficient analytical approach that requires no sample pretreatment or front-end separation.