The sour leaf that ranks first in iron

A plate of Andhra food arrives with three kinds of sour on it and no lemon. There is tamarind in the dal, there is raw mango in the summer pickle, and there is a dark green paste at the edge of the plate that tastes like all the sourness in the meal has been concentrated into a vegetable. That paste is gongura, and it is the reason this part of the country can treat sourness as a main flavour rather than a correction.

Every cuisine has a sour note. Most of them get it from a fruit: lemon in the eastern Mediterranean, lime in the Gulf, tamarind in Southeast Asia, vinegar in northern Europe. The Deccan gets a great deal of its sourness from a leaf, and that choice has consequences that go past taste. A leaf that is sour is also a leaf, which means it arrives with fibre, minerals and vitamins attached. Whether that is a good bargain depends on which of them you needed.

What the leaf is

Gongura is a hibiscus, grown as a shrub, harvested by stripping leaves from stems that can reach two metres. It has a dozen names and each one describes it differently. In Telugu it is gongura. In Tamil it is pulicha keerai — sour leaf — which is the most honest of the names. In Kannada, pundi soppu. In Hindi and Marathi, ambadi. In Bengali, mestapaat. In Odia, khata palanga: sour spinach. Only the botanical name is supposed to settle the question, and it does not, because two species are in play and the sources disagree about which one is on the plate.

Two forms are sold side by side in every market that carries it. The green-stemmed one is milder and belongs to coastal Andhra; the red-stemmed one is noticeably sourer, has anthocyanins in the stem, and is the one Telangana cooks ask for. The difference is not cosmetic. It changes how much of the paste you can eat at once, and it changes what the dish is for.

The number that makes it unusual

Here is where the leaf stops being a flavour and becomes a supply. Per 100 g of fresh leaf, gongura carries 7.65 mg of iron in the green form and 9.56 mg in the red — the highest figure in a table of 26 green leafy vegetables, ahead of every spinach, amaranth, drumstick leaf and colocasia in the set. The same 100 g has 36 kcal, 1.9 g of protein, 4.6 g of fibre, 5,285 µg of beta-carotene, 433 µg of vitamin K and 75 µg of folate.

That is a strange set of numbers for a leaf that most of the country has never eaten. Spinach is famous for iron and carries about a third of this. The comparison is worth making because it explains why gongura is not a garnish in the Deccan but a bulk ingredient: it is doing the job a dal or a meat would otherwise do, in a region where both were expensive for most of the year.

Why sourness is a main flavour here

In a temperate kitchen, acid is a finish. You squeeze it on at the end to lift a heavy dish. In the Deccan it is a component, present in quantity, balanced against chilli and fat rather than used to cut through them. There are practical reasons and the leaf is only one of them: tamarind grows here, raw mango is a season, and the summer pickle shelf exists because the hot months are long.

But sourness also does something specific to a meal eaten at 40°C. It makes you salivate, and saliva makes dry food go down; it makes water taste like more than water; and it covers the flat, metallic taste of a leafy green cooked to nothing. A cuisine that has to get a large volume of leaves and lentils into people in May has an interest in sourness that a cuisine built on butter and bread does not.

The dish, and why it is built that way

Gongura pachadi is the standard form and it is short: leaves washed and dried, wilted in a pan until they collapse and lose their raw edge, then ground with roasted dried red chillies, garlic and salt, and finished with a tempering of mustard seed and fenugreek in hot oil. Every step has a reason that the recipe does not state.

Wilting drives off water, which concentrates the acid and stops the paste fermenting in two days. Roasting the chillies rather than frying them gives a toasted note that survives the grinding. Garlic is antimicrobial as well as flavouring, which matters in a preparation that is kept for a week without refrigeration. Fenugreek is bitter and slightly mucilaginous, and that texture is what stops a sour paste from tasting thin. And the oil is not there for richness: beta-carotene is fat-soluble, so a dish cooked without enough fat delivers the colour and leaves the vitamin in the bowl.

The one thing the recipe does that nobody planned is the interesting one. Vitamin C enhances non-haem iron absorption; oxalate inhibits it. Gongura contains both, and the traditional method — a fast cook, an acid medium, a lot of fat, garlic and no long soaking — happens to be a method that keeps the vitamin C and does not add another source of oxalate. Whether the women who developed it knew any of this is unknowable. That the method works is measurable.

The pickle is the point

Fresh gongura is a monsoon-to-autumn leaf; the plant is cut back and the leaves stop. So the leaf is also made into a pickle with salt, chilli and oil, packed tight, and eaten through the months when there is none — which puts it in the same category as every other Indian preserve: a machine for moving one season's glut into another season's absence. In Guntur and the districts around it, a jar of gongura pickle is standard household equipment, and the oil layer on top is the seal.

There is a version of this story that ends with a superfood label and a exported powder. It would not be wrong about the numbers and it would miss the point. The leaf is interesting because it is a solution to a local shortage — no lemons inland, iron hard to come by, green vegetables scarce for half the year — and because the solution is a single plant that answers three of those shortages at once with the same tissue.

Look at the pillar's four variables together and gongura is the neatest case of the fourth one. Grain decides the plate. Fat decides the flavour. A date decides the chilli. And absence decides what a cuisine invents: where there is no lemon, there is a sour leaf, and the sour leaf turns out to be the best source of iron in the garden. That is not a coincidence anybody arranged. It is what happens when a kitchen is forced to be literal about what it has.

This is entry 18 of Food in About India. The pillar's argument — grain and fat, not spice blends — is set out on the pillar page.