Kaeng Som

Central Thai sour fish curry: an austere, fiercely sour broth of dried chilli paste and tamarind with fish and seasonal vegetables, served over jasmine rice

Origin: Central Thailand

From the journey of Chilli Pepper.

Kaeng som (แกงส้ม), literally sour curry, is one of the oldest and most widely eaten curries of central Thailand: a clear, intensely sour and spiced broth built on a dried chilli paste base and sharpened primarily with tamarind, containing fish or prawns and seasonal vegetables. It stands apart from virtually every other Thai curry. There is no coconut milk, no warm spice blend, no richness or creaminess to moderate the heat or the sourness. Kaeng som is defined by its austerity and its acidity; where massaman is built for the comfort of long-braised richness and kaeng khiao wan for the perfumed freshness of green chilli and basil, kaeng som makes no concessions. The curry paste for kaeng som is deliberately spare: dried red chillies, shallots, and fermented shrimp paste (kapi), with turmeric added in the southern Thai version, which carries the alternative name kaeng lueang (yellow curry). The broth is water-based, brought to a simmer and seasoned with fish sauce. The sourness arrives from two directions: tamarind water, which is the classical and primary souring agent throughout the central Thai tradition, and cherry tomatoes, a Bangkok adaptation in which the tomatoes are added with the vegetables to contribute both an additional layer of acidity and a brightness of colour that rounds out the tamarind's deeper, darker sourness. The protein is invariably fish or prawns: whole fish fillets or firm white fish such as sea bass or tilapia, or large raw prawns. Pork and chicken are not traditional in the central Thai version; the clean, marine character of fish or shellfish suits the sharpness of the broth. Vegetables vary by season: white radish, pak choi, green beans, and Chinese cabbage are the most common. Kaeng som is served ladled directly over steamed jasmine rice, with fresh raw cucumber or spring onion alongside to cool the palate against the broth's assertive heat.

Ingredients

Curry Paste

  • 8 large dried red chillies, stems and seeds removed, soaked in warm water for 10 minutes and drained
  • 4 shallots (approx 80g), peeled
  • 1 tsp kapi (Thai fermented shrimp paste), dry-roasted in a dry pan for 30 seconds per side, or wrapped in foil and grilled
  • 0.25 tsp ground turmeric (for colour; traditional in the southern version, optional in the central)
  • 0.5 tsp fine salt

Broth

  • 1 litre fish stock, or water
  • 3 tbsp tamarind water (2 tbsp tamarind paste dissolved and strained from 4 tbsp warm water)
  • 2.5 tbsp fish sauce (nam pla), plus more to taste
  • 1 tsp palm sugar or light brown sugar

Protein and Vegetables

  • 400 g firm white fish fillets (sea bass, tilapia, or snapper), cut into 3cm pieces; or 300g large raw prawns, peeled and deveined
  • 150 g white radish (daikon), peeled and sliced 1cm thick
  • 100 g green beans, trimmed and cut into 4cm lengths; or 1 small pak choi, separated into leaves
  • 100 g cherry tomatoes, halved

To Serve

  • To serve: steamed jasmine rice, fresh cucumber sliced, spring onion trimmed

Method

  1. Make the tamarind water: place the tamarind paste in a small bowl, add 4 tablespoons of warm water, and work the pulp with your fingers to dissolve it fully. Strain through a sieve, pressing the solids firmly to extract all the liquid. Discard the fibres and seeds. Set aside.
  2. Pound the curry paste: in a mortar, pound the drained soaked chillies with the salt until broken down. Add the shallots and dry-roasted kapi; pound until a smooth, cohesive paste forms. Stir in the turmeric. Alternatively, blend in a small food processor with 2 tablespoons of water to help the blades move.
  3. Bring the fish stock (or water) to a steady simmer in a medium saucepan. Add the curry paste and whisk to dissolve it completely into the broth. Simmer for 3 minutes.
  4. Add the tamarind water, fish sauce, and palm sugar. Stir well and taste: the broth should be simultaneously sour, salty, and hot, with a clear, clean flavour. Adjust with more tamarind water for sourness or fish sauce for saltiness.
  5. Add the white radish. Simmer for 5 minutes until just beginning to soften.
  6. Add the fish or prawns, green beans or pak choi, and cherry tomatoes. Simmer for 3 to 4 minutes until the fish is just cooked through and the vegetables are tender but retain a little bite. Do not overcook the fish.
  7. Taste once more and adjust the seasoning. Ladle directly over steamed jasmine rice in deep bowls. Serve with sliced cucumber and spring onion alongside.

Notes

Tamarind is the primary souring agent in kaeng som; cherry tomatoes are an addition of the Bangkok and central Thai adaptation that adds brightness and co-acidity. In the more austere traditional version, the tomatoes are omitted entirely and the full sourness comes from tamarind alone. For the southern Thai version (kaeng lueang, yellow sour curry), increase the turmeric to 1 teaspoon and substitute pineapple chunks for some or all of the white radish, adding them with the fish. Kapi is essential to the depth of the paste; without it the broth will taste thin and one-dimensional. Both fish and prawns work well in the same recipe; if using both together, add the prawns 2 minutes after the fish as they cook slightly faster.

The Gastrographer

The Gastrographer

Mapping Culinary History

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Journey Point Map Key

Ingredient originTrade or transit route
Became a culinary stapleColonial / trade control
c. 1800 CE
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19 of 19 stops
1800 CE
6000 BCE1530 CE1555 CE1800 CE
Chilli Pepper

Chilli Pepper

Capsicum spp.

VegetablesSpices & AromaticsNightshades

🌍Origin

Central and South America. — c. 6000 BCE

🌱Domestication

The chilli is not a single domesticated plant but a whole genus, Capsicum, brought into cultivation many times over by many peoples across the breadth of the Americas, and its extraordinary diversity is the direct record of that repeated, independent domestication. The wild ancestors of the genus arose in the highlands of what is now Bolivia and the surrounding lowlands of South America, small-fruited, bird-dispersed plants whose pungent berries spread across South and Central America long before any human cultivated them. Five species were eventually domesticated, each in a different region and from a different wild stock, and it is this multiplicity, rather than any single founding event, that gives the chilli its bewildering range of form, colour, and heat. The most consequential of these domestications produced Capsicum annuum, the species that today encompasses the great majority of the world's cultivated chillies and sweet peppers alike. It was taken into cultivation in central and southern Mexico no later than 6000 BCE, and possibly considerably earlier: desiccated seeds and pod fragments recovered from the dry caves of the Tehuacán Valley in Puebla and from sites in Tamaulipas demonstrate that Mesoamerican peoples were growing and selecting the plant by that date, amongst the earliest of all American crops. From this single species, through millennia of patient selection, came the dried ancho (the ripened poblano), the smoked chipotle (the dried, smoked jalapeño), the fruity mulato, the searing chile de árbol, the deep guajillo, and the long vocabulary of named Mexican chillies that no other cuisine has matched. Quite separately, the civilisations of South America domesticated their own species from their own wild ancestors. Capsicum chinense, the species of the habanero and the Scotch bonnet, with its rising, aromatic, floral heat, was brought into cultivation in the Amazonian lowlands and carried northward into the Caribbean. Capsicum baccatum, the ají amarillo family that gives Peruvian cooking its golden colour and fruity warmth, was domesticated in the Andean valleys and coastal oases of Peru. Capsicum pubescens, the thick-walled, black-seeded rocoto, was selected in the high Andes at altitudes no other chilli could tolerate, and Capsicum frutescens spread as a semi-domesticated bird pepper across the lowland tropics. By the time of European contact, the peoples of Mesoamerica and the Andes between them had developed hundreds of distinct cultivars, each chosen for a particular flavour, heat, colour, and use, a breeding inheritance of more than ten thousand years that the rest of the world would receive, all at once, after 1492.

Global Voyage

The diffusion of the chilli out of the Americas, beginning with the return of Columbus in 1493, is one of the swiftest and most complete migrations of any food plant in the whole of history. Where the potato, the tomato, and maize took generations to overcome suspicion and become European staples, the chilli was adopted across Africa, Asia, and the warmer parts of Europe within a single century, and in many regions it so thoroughly displaced the native sources of heat that it now seems indigenous. Columbus himself carried the first pods back to Spain from the Caribbean, where he had met the aromatic Capsicum chinense of the Taíno and named it 'pepper' by analogy with the black pepper of the Indies he had been sent to find; the misnomer has clung to the plant in nearly every European language ever since. The primary engine of the chilli's spread was not Spain but Portugal. The Portuguese maritime empire of the sixteenth century, the most geographically extensive trading network in the world, ran from Lisbon south along the West African coast, around the Cape of Good Hope, and on to Goa, Malacca, Macau, and Japan, and the chilli travelled these routes along the very sea lanes that had carried black pepper for centuries. The irony was considerable, for the chilli offered heat far cheaper and easier to grow than the spice it partly replaced, and lands that had once priced pepper in gold took up the chilli with practical enthusiasm. Portuguese ships planted it on the Guinea coast, where West African cooks who already prized the heat of grains of paradise embraced the Scotch bonnet so completely that it became the defining chilli of the region; carried it to Goa, where it entered the vindaloo and spread inland across India within a century, displacing long pepper; and brought it to Malacca, Sumatra, and the Siamese port of Ayutthaya, where it transformed the sambal and the curry paste of Southeast Asia. A second, wholly distinct route ran across the Pacific. The Manila Galleon, the annual Spanish service that linked Acapulco in New Spain to Manila from 1565, carried the chilli westward directly from Mexico into the Philippines and onward into the coastal provinces of southern China, so that Sichuan and the Fujian coast received the plant from two directions at nearly the same moment, the Portuguese stream moving inland from the south coast and the Spanish stream arriving by way of the Pacific. There it met the indigenous Sichuan pepper to create the numbing, burning málà flavour that now defines the region's cooking. A third route was Ottoman: from the Iberian Mediterranean and through Egypt the chilli entered the Ottoman world, where it became the Aleppo pepper of the Levant and the Anatolian table, and travelled north with Ottoman soldiers and administrators into the Balkans and Hungary, where two centuries of selection turned it into paprika. By way of these three great networks, Portuguese, Spanish, and Ottoman, a clutch of American plants reached the kitchens of Africa, Asia, and Europe in the span of a hundred years, and from Korea's gochujang to Ethiopia's berbere to Hungary's goulash the chilli was absorbed so deeply that it became inseparable from the cuisines that received it.

🍽Modern Culinary Role

The chilli is consumed today by more human beings than any other spice or flavouring, with an estimated 80 per cent of the world's population eating some form of it daily, and it is grown across every warm and temperate region on earth, with India, China, and Mexico amongst the largest producers. Its work in the kitchen falls into three broad registers. As a fresh ingredient it supplies heat, aroma, and bright flavour to Mexican salsas, Thai and Vietnamese salads, Indonesian raw sambals, and the relishes of East Africa. As a dried, ground, or smoked spice it becomes Hungarian paprika, Spanish pimentón, Aleppo pepper, Indian chilli powder, and Korean gochugaru, each a regional product as distinct from the others as one wine region is from another. And as a fermented or preserved paste it underpins whole cuisines: Korean gochujang, North African harissa, Chinese doubanjiang, Indonesian and Malaysian sambal, and the pepper sauces of West Africa. The heat itself is the work of a single family of compounds, the capsaicinoids, of which capsaicin is the most abundant; they bind to the same receptors that register physical heat and abrasion, so that the mouth is fooled into feeling a burn where there is no actual injury. The body answers this false alarm with a flood of endorphins, and it is this paradox, a pain that the brain rewards with pleasure, that has made the chilli the most compelling and the most addictive of all the world's seasonings. The heat is now measured on the Scoville scale, and competitive breeding has driven cultivated varieties to extremes their wild ancestors never approached. No plant carried by the Columbian Exchange has been more completely absorbed into the cooking of the wider world than the chilli. Where the potato and the tomato took centuries to win acceptance, the chilli was embraced with total commitment within a generation of its arrival in every region it reached, until the cuisines of Sichuan, Korea, Thailand, India, Ethiopia, Hungary, and West Africa became, in the modern imagination, unthinkable without it, despite the plant having been unknown to all of them before 1500. It is the rare ingredient that travelled the entire globe and was naturalised everywhere as though it had always belonged.

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