Vol. XXIX · The Cuisines of India Plate 9 of 11South India, idli, dosa, fermented batter, urad dal, rice, Leuconostoc, lactic acid bacteria, fermentation, pH, sambar, rasam, coconut, tamarind, curry leaves, Kerala, Tamil Nadu, Karnataka, AndhraMS

The South.

In Chennai an idli batter rises overnight on the counter. In a cold European kitchen the same batter may sit for a day and barely move.

The cooking of Tamil Nadu, Kerala, Karnataka and Andhra Pradesh is built on rice, eaten at every meal, and on lentils, coconut, tamarind, black mustard seed and curry leaves (XXIX.1). Sambar is a tamarind-sour stew of toor dal and vegetables with sambar powder (XXIX.3); rasam a thin, peppery tamarind-and-tomato broth; Kerala cooks with coconut milk and coconut oil, and with seafood along the coast; Andhra is famous for fierce chilli heat. Meals are often served on a banana leaf, rice at the centre, with a sequence of curries, dal, rasam and curd rice to end.

Idli and dosa are the triumph of fermentation (XIV.3). Rice and urad dal are soaked separately, ground with water — the dal to a fluffy, mucilaginous paste that traps gas — mixed with salt and left 8–14 hours in a warm place. Lactic acid bacteria, especially Leuconostoc, and wild yeasts that come from the grains and the cook's hands multiply; their carbon dioxide raises the batter to nearly double, and their lactic acid sours it and lowers its pH towards 4.5. The thick batter is steamed in idli moulds into soft, spongy cakes; thinned and spread on a hot griddle it becomes crisp dosa. In cool weather, fermentation slows sharply; cooks put the batter in a switched-off oven with the light on. The workshop ferments a batter.

Below: the rise and the pH of an idli batter over the hours you choose at the kitchen temperature you choose (teaching model: logistic growth with its midpoint at 8 hours at 30 °C, doubling in time for every 10 °C cooler), with the ready point.

What you will learn
Workshop
Teaching model, after published idli fermentation studies (volume nearly doubling and pH falling from about 6.2 to 4.5 in 12–14 hours at 28–32 °C): rise = 1 + 1.2 × logistic((t − t½) ÷ 1.5), pH = 6.2 − 1.7 × logistic((t − t½) ÷ 2.5), each scaled to start at its initial value; t½ = 8 h × 2^((30 − T) ÷ 10). Ready: risen 1.8 times and pH 4.8 or below.

Warmth is the recipe

In the teaching model a batter at 30 °C is ready in about 12 hours — overnight; at 25 °C about 17; at a cool 20 °C about 24, a whole day. Cooks in cold kitchens keep the batter warm rather than wait: in an oven with only the light on (about 30 °C), wrapped in a towel, or with a little more salt held back until morning. Over-fermented batter turns very sour and runny; refrigerate it once it has risen, where it keeps three or four days.

Idli batter (about 30 idlis): soak 300 g idli rice (or parboiled rice) and 100 g whole skinned urad dal separately 6 hours. Grind the dal with about 150 mL cold water until white, light and fluffy (10 minutes in a wet grinder or in short bursts in a blender, keeping it cool); grind the rice to a slightly coarse paste with about 200 mL water; mix them with 1½ tsp salt by hand in a large bowl, cover loosely and leave warm 8–14 hours until doubled and sour-smelling. Stir gently, fill oiled idli moulds and steam 10–12 minutes; serve with sambar and coconut chutney. For dosa, thin the batter with water and spread a ladleful in a spiral on a hot, lightly oiled griddle.

At the stove

Divide a batter into two jars, keep one at room temperature and one in a warm oven with the light on. Mark the levels and check them in the morning.

Idli appears in Kannada texts of the tenth century, but early recipes do not mention fermentation; food historians such as K. T. Achaya suggested the fermented version may have arrived from Indonesia, where similar fermented rice cakes are made, between the eighth and twelfth centuries.

Terms

Idli
Steamed cakes of fermented rice and urad dal batter.
Dosa
Thin crisp pancake of the same batter.
Leuconostoc
Lactic acid bacterium that leavens and sours the batter.
Sambar / rasam
Tamarind-lentil stew / thin peppery broth.
South Indian cooking: rice, lentils, coconut, tamarind, curry leaves. Idli and dosa batter ferments with lactic bacteria and yeasts: it nearly doubles and sours to pH ~4.5 in about 12 hours at 30 °C — much longer when cool.

Sources

  1. K. T. Achaya, Indian Food: A Historical Companion, Oxford University Press, 1994; and A Historical Dictionary of Indian Food, 1998.
  2. A teaching value chosen for the course: the right order of magnitude and shape, not a measurement of a particular food.