Storing dahi, pickles and tamarind: acidity and steel
The most acidic things in an Indian kitchen are exactly the things stored longest. Here is what that means for the container.
Curd, pickle, tamarind pulp and chutney share two properties: they are acidic, and they sit in storage for a long time. That combination is precisely the test of a storage material.
Curd and dahi
Lactic acid gives dahi its tang, and it is mild as acids go, but the contact is long.
Steel is entirely comfortable with this. Curd sets well in steel, does not pick up any flavour from the vessel, and the vessel washes clean without holding on to the smell — which is more than can be said for a plastic tub that has held dahi for a week.
For setting, a wide, shallow vessel gives a more even set than a deep narrow one because the whole mass reaches setting temperature at a similar rate.
Pickles: the one to think about
Achar is the genuinely demanding case, because it combines three things:
- High acidity, from lemon, vinegar or fermentation.
- High salt, often very high.
- Very long storage — months, not days.
Salt is what deserves care here. Chlorides in prolonged contact are the one thing that can break down steel's passive layer.
For short-term working stock — a few days of pickle in the kitchen — steel is fine. For long-term maturing, traditional practice uses glazed ceramic or glass, and that tradition is sound. We would rather say so than pretend otherwise.
If you do keep pickle in steel:
- Keep the pickle submerged in oil; the oil layer excludes brine from the metal.
- Do not leave the vessel part-empty with brine drying on the walls.
- Wash and dry thoroughly between batches.
Tamarind
Tamarind is strongly acidic and completely unproblematic in steel. It will not pick up metal taste and it will not pit the vessel. Note that tamarind is mildly abrasive chemically in a useful way — it is the traditional method for cleaning tarnish off copper, which is why the copper base of a lagan brightens if you happen to spill some on it.
Chutneys and wet masalas
Ground chutneys — coriander, mint, coconut — are acidic and oxidise quickly. Steel helps here in a way people do not expect: it conducts heat well, so a steel container placed in the fridge chills its contents faster than plastic, and cold slows the oxidation that turns green chutney brown.
A simple rule
Acid alone: steel is ideal. Acid plus heavy salt plus months of storage: use glass or glazed ceramic.
Everything else in an Indian kitchen falls comfortably into the first category.
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