We were trying the litmus paper test and we found out that tea is acidic. So the question came in my mind and my science teacher could not give me any satisfactory answer: what acids are found in tea?
Some of the major components of tea are polyphenols. They are fairly acidic and may dominate the pH of tea.
For some examples of the types of polyphenol that are common see this site on tea chemistry:
The major flavanols [a specific type of polyphenolic compounds] in tea are: catechin (C), epicatechin (EC), epicatechin gallate (ECG), gallocatechin (GC), epigallocatechin (EGC), and epigallocatechin gallate (EGCG).
from which some degree of acidity is likely to result from all those phenolic OH groups.
According to this analysis from 1965, there are several different acids in tea leaves:
Succinic, oxalic, malic, citric, isocitric, and five unknown acids have been found at appreciable levels (>0·1 μequiv./g. fresh wt.) in tea shoot tips. The major acids quantitatively were oxalic, malic and citric acids. The acids studied were recovered quantitatively from plant extracts, but they accounted for less than one-fourth the total acidity present in tea shoot tips.
However, some of these acids degrade as the leaves go from the plant to your teapot, in particular during the withering process:
Changes in the levels of organic acids take place in tea shoot tips during the manufacture of tea which are typical of senescing plant tissues. Notably, the levels of succinic and malic acids are markedly reduced during withering. The level of oxalic acid, however, remains nearly constant throughout manufacture.
Unfortunately, the full article is behind a paywall and I don't have access to further details.