Tempering in Fat.
Mustard seeds dropped into hot oil crackle and pop within seconds; boiled in water, they stay bitter and almost odourless. The fat and the heat do the work.
The aromas of spices are mostly small oily molecules — terpenes, phenols, aldehydes — and like the capsaicin of chilli they are far more soluble in fat than in water (XI.8). Chemists measure this by the octanol–water partition coefficient: most spice aromas prefer the oily phase by a hundred to a thousand times. Frying spices in fat therefore pulls their aroma into a medium that coats the tongue and carries it through the dish, while heat breaks open the seeds, drives Maillard and caramel reactions on their surfaces (VIII.1) and turns harsh, raw notes toasty: mustard seed's bitterness becomes nutty, cumin's sharpness warm.
The method is about order and timing, because each spice browns at its own rate. Heat ghee or oil until it shimmers; add seeds that need the most heat first — black mustard until they pop, then cumin until it darkens a shade; then dried red chillies and curry leaves, which spit; then a pinch of asafoetida, a few seconds only; and ground spices last, off the heat or with a splash of water, because powders burn in seconds. A tadka poured sizzling over dal (XXIX.5) or a raita is a finish; one that begins a curry is the base on which onions and tomatoes are cooked (XXIX.4). The workshop dissolves an aroma.
Below: the share of each spice compound held in the fat of a dish rather than its water, for the fat content you choose (exact two-phase partition from the octanol–water coefficient, approximate published logP values), and the order in which a South Indian tadka goes into the pan.
- Explain why spices are fried in fat.
- Temper spices in the right order.
- Use a tadka to start or finish a dish.
- Avoid burning ground spices.
Hot fat, right order, seconds not minutes
With 8 % fat in a dish, about 0.99 of a compound like capsaicin or linalool sits in the fat — almost all of it — and even with 1 % fat, mustard's pungent isothiocyanate is 0.56 in the fat; with a mere trace, 0.1 %, still 0.11. A dal cooked without fat is flat for this reason; the tadka puts both fat and the fried aromas into it at the end, where they stay on the surface, fragrant.
A South Indian tadka for dal for 4: heat 2 tbsp ghee or oil in a small pan until it shimmers; add 1 tsp black mustard seed and cover — when the popping slows (about 30 seconds), add 1 tsp cumin and 1 tsp urad dal and stir until the dal turns golden; add 2 broken dried red chillies and 10 curry leaves (stand back — they spit), then a pinch of asafoetida; after 3 seconds pour it all, sizzling, over the dal. For a northern tadka use ghee, cumin, sliced garlic until golden, dried chilli and, off the heat, a pinch of Kashmiri chilli powder for colour. If anything turns black and smells acrid, start again: burnt spices are bitter (VIII.8).
Boil a pinch of mustard seeds in water and fry another pinch in hot oil until they pop. Taste each.
Terms
- Tadka
- Spices fried in hot fat to start or finish a dish.
- Partition coefficient
- How much more soluble a molecule is in oil than water.
- Blooming
- Releasing spice aroma by frying in fat.
- Ghee
- Clarified butter, the classic tempering fat.
Sources
- NIST Chemistry WebBook (SRD 69): normal boiling points and enthalpies of vaporisation; octanol–water partition coefficients (log P) from PubChem. Vapour pressure from the Clausius–Clapeyron equation.
- H. McGee, On Food and Cooking: The Science and Lore of the Kitchen, 2nd ed., Scribner, 2004.
- K. T. Achaya, Indian Food: A Historical Companion, Oxford University Press, 1994; and A Historical Dictionary of Indian Food, 1998.