Mechanism of aroma enhancement methods in accelerating Congou black tea acidification subjected to room temperature storage.

• Acidification can occur during storage of Congou black tea. • Aroma enhancement process (AEP) accelerates acidification of black tea during storage. • AEP promotes conversion of Phenylalanine and glucose to oxalic acid, quinic acid, etc. • AEP also changes tea soup composition and increases acidification during storage. Acidification of aroma-enhanced black tea during storage was studied. UPLC-Q-TOF/MS (Ultra Performance Liquid Chromatography and Quadrupole-Time of Flight Mass Spectrometer) and HPLC (High-Performance Liquid Chromatography) analysis of non-volatile substances and organic acids revealed a decrease of soluble sugars and amino acids in aroma-enhanced black tea, while an increase in organic acids such as oxalic acid, malic acid and quinic acid. Further in vitro experiments indicated that the acidification of aroma-enhanced tea during storage can be attributed to decomposition of sugars and amino acids by heating, oxidation of aromatic aldehydes. Meanwhile, the amino acids, catechins, soluble sugars and flavonoids that constitute the taste of black tea are further reduced, changing the taste composition of tea infusion and further increasing its acidity. This study revealed the reasons for black tea acidification during aroma enhancement and storage and provided a theoretical basis for improving black tea quality. [ABSTRACT FROM AUTHOR]