Discovery and identification of novel color compound formed from EGCG upon heating: Integrated multispectral, sensory evaluation, metabolomics, and nuclear magnetic resonance

(−)-Epigallocatechin gallate (EGCG) is the major catechin in tea. However, its transformation mechanisms into sensory-active compounds during tea roasting remain unclear. LC-MS-based metabolomics and multispectral analysis discovered a variety of novel color compounds (NCCs) formed from EGCG during high-temperature heating, and these compounds were positively correlated with color indexes. The critical NCC1 was identified, with a color dilution factor of 14 and taste thresholds for bitterness and astringency at 35.61 μM. The effects of substrate ratio, temperature, time, and pH on NCC1 content were explored, revealing that (−)-epigallocatechin (EGC) contributed to its formation. The NCC1 content ranged from 0.03 to 448.03 μM under different in vitro conditions. The content of NCC1 in tea roasted for different times ranged from 1.25 to 3.59 μM. The present study provides a basis for exploring how sensory-active compounds are formed from catechins in tea during high-temperature roasting, and for evaluating their properties.