In February 2024, the Molecular Sensory Science team from the School of Food and Health published a research paper titled "In Situ Oral Metabolism Analysis of Astringent Compounds in Tea by Paper Spray Mass Spectroscopy, Electrospray Mass Spectroscopy, Turbidity and Sensory Evaluation" in the international journal "Journal of Agricultural and Food Chemistry".

In this paper, the changes of oral astringency intensity with time after tea drinking were determined by quantitative description and analysis, and the phenolic substances in tea were identified by electrospray ionization mass spectrometry. Then, based on in vivo experiments, the metabolic patterns of phenolic compounds in tea after drinking tea in the oral saliva environment were studied. The study found that the oral metabolism of phenolic compounds in tea after drinking tea is a long-term process, and the key perceptual area for the astringency of tea is the tongue surface. In addition, based on in vitro experiments to explore the metabolic patterns of phenolic substances in tea in the saliva environment, the study found that the optimal reaction time between phenolic substances in tea and saliva proteins is 30 minutes. Prolonged reaction time and high temperature can enhance the interaction between phenolic substances in tea and saliva proteins, but excessive reaction temperature can also disrupt this binding.

In this study, combined with sensory evaluation and paper spray mass spectrometry, a method for in situ detection of phenolic substances in tea after tea drinking was developed, which can accurately sample from the mouth. The combination of multiple methods to analyze the metabolic patterns of phenolic substances in saliva environment from both in vivo and in vitro perspectives is innovative.

Figure A. Qualitative detection results of phenolic substances in tea; B. The residual amount of phenolic substances in the oral cavity at different times after drinking tea; C. The residual levels of phenolic substances in different oral parts after drinking tea; D. Changes in the content of phenolic substances in green tea saliva mixture at different reaction times; E. Changes in the content of phenolic substances in green tea saliva mixture at different reaction temperatures