My tea tastes sour or acidic

In short

Sourness is a taste, and it is a different taste from both of the faults tea writing usually discusses. Bitterness comes from catechins and caffeine and is driven by temperature and time; astringency is not a taste at all but the drying grip of polyphenols binding saliva proteins. Sourness is acid, and every cup of tea has some — tea liquor is mildly acidic by nature. It becomes a fault only when something has raised it, and the four things that raise it are different enough that the cause decides whether the tea is recoverable.

Likely causes, in order

Most likely first. Answer the question under each one before moving on — several of these look alike in the cup and are told apart only by what was done to the leaf.

1. 1. There is fruit, hibiscus or rosehip in the blend and the acid is an ingredient

   Leaf quality

   Check: Read the ingredients rather than the name. Does the blend contain hibiscus, rosehip, apple, citrus peel or 'fruit pieces' — and is the dry mix noticeably red or pink?

   Fix: Then the sourness is the product. Hibiscus in particular is strongly acidic and is used in blends precisely for that tartness; it will dominate any tea it is mixed with and no brewing change removes it. This is worth ruling out first because it is the commonest answer for anyone drinking supermarket 'fruit tea', and because it costs nothing to check.

2. 2. The tea was steeped long and strong, which raises acidity along with everything else

   Over-extraction

   Check: Was this a long steep, a large dose, or the last cup out of a pot that had been standing? Does a deliberately short, light brew of the same leaf taste clean?

   Fix: If the short brew is clean, this is a brewing fault and it is fully reversible. A heavily extracted or long-standing infusion is measurably more acidic than a fresh light one, which is why the last cup from a stewed pot is both the harshest and the one most likely to curdle milk. Brew shorter, dose lower, and decant off the leaf rather than leaving the pot to stand.

3. 3. Moisture reached the dry leaf and acidity developed in storage

   Storage

   Check: Smell the dry leaf on its own. Is the sourness there before any water is added, and does it sit alongside a musty, damp-cardboard or cellar note rather than alongside sweetness?

   Fix: Sour plus musty in the DRY leaf is a storage failure rather than a brewing one, and it does not brew out. Leaf that has taken on damp does not recover and drying it does not restore it. Replace it, and check what the container was doing: the usual causes are a tin filled before it was fully dry, storage near a kettle or hob, or a resealable pouch that was folded rather than closed.

4. 4. It is a lactic-fermented tea and the sourness is the entire point

   Leaf quality

   Check: Is this a Japanese goishicha or awabancha, a Burmese laphet, a Thai miang, or another fermented leaf product rather than an ordinary tea?

   Fix: These are made by lactic-acid fermentation and are supposed to be sour in the way a pickle is supposed to be sour. The same word therefore names a defect in one category and the defining character of another, which is why identifying what you are holding comes before judging it. Nothing needs fixing.

5. 5. It is a dark tea, where sourness carries much more specific information

   Leaf quality

   Check: Is this a sheng or shou pu-erh, a Liu Bao or another dark tea?

   Fix: Stop here and use the dark-tea record instead. In that category sourness is the single most diagnostic fault there is — it separates a young sheng brewed too hard from an unrested wet pile from storage that ran too wet, and those three have completely different outlooks. This record's general answers are too coarse for it.

Brewing methods this applies to

• Western brewing (teapot or mug) — A small amount of leaf in a large volume of water, steeped once for a few minutes and then strained off. The approach most English-speaking drinkers already know, and the one most teas sold in the West are made for.
• Mug infuser brewing — Loose leaf in a basket inside a mug — the most common way loose tea is actually made, and the method most often responsible for people concluding that loose leaf is not worth the trouble.

When this cannot be fixed

Where the sourness is in the dry leaf and comes with a musty note, the tea is finished. That combination means moisture, and moisture is the one storage fault that does not reverse — airing, re-drying and hotter brewing all fail, because what changed is the leaf rather than the infusion.

Related problems

Sharing a cause category, a tea type or a brewing method with this one.

• My tea arrived broken, with dust at the bottom of the packet — Whole-leaf tea bought at a whole-leaf price contains a lot of fragments, and there is fine material in the bottom of the bag.
• My tea is harsh and I cannot tell whether it is bitter or astringent — The cup is unpleasant in a way that is hard to name, and every piece of advice about it assumes you already know which of the two words applies.
• My Japanese green tea tastes of seaweed or fish — A sencha, gyokuro or matcha reads as marine — seaweed at best, distinctly fishy at worst — and it is not clear whether that is the tea or a fault.
• My tea came out too strong — can I just add water? — A cup or pot is far stronger than intended, and the obvious response is to dilute it.
• My tea gets drier and harsher as it cools — The first mouthful is balanced and the last one, several minutes later, grips the tongue and feels rough — from the same cup, with nothing added.

Sources