Simultaneous detection of amino acids and short-chain fatty acids in tea using rapid pre-column derivatization coupled with GC–MS: Exploring their spatial distribution in tea trees and the impact of processing techniques on their content

Amino acids (AAs) and short-chain fatty acids (SCFAs) are key to tea's flavor and health benefits. This study developed a novel GC–MS and GC-FID method using rapid (3 min), high-sensitivity (0.00062 μg mL −1  < LOD < 0.04964 μg mL −1 ) pre-column derivatization with propyl chloroformate to simultaneously measure 17 AAs and 9 SCFAs. The spatial distribution analysis revealed total AAs and theanine were enriched in tender stems, buds, and tender leaves, while mature and older leaves had lower concentrations. Within the same leaf, theanine, glutamic acid, and acetic acid are primarily located near the leaf veins. Six teas from the same raw material were analyzed for processing impacts, showing green, white, yellow, and oolong teas had higher AA and theanine levels than black and dark teas. Certain dark teas exhibited elevated acetic acid levels compared to other teas. This study enhances our understanding of AA and SCFA profiles, providing valuable insights for tea research.