Editors' Note: Nik Sharma's new book, The The Flavor Equation: The Science of Great Cooking Explained in More Than 100 Essential Recipes, comes out in October 2020. You can pre-order it anywhere books are sold.
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There are many ways to coax the flavor out of dried spices, but in India, they’re often bloomed in hot fat. That technique produces an infused oil called tadka, also known as chaunk (chhonk), baghaar, and many other names. The word tadka is used both to refer to the cooking method and the spiced liquid fat.
Though many cooking techniques evolved out of necessity and practicality, I’m fascinated by the science behind them, which often proves why they work. It’s what led me to write my forthcoming book, The Flavor Equation: The Science of Great Cooking Explained, out this October. With many spices (and even herbs), the aromatic molecules responsible for flavor are highly volatile. Drying spices “freezes” these flavor molecules in place (to a certain extent, and for a limited amount of time), and increases their shelf life. But drying also reduces the strength of their aroma and taste. Cooks across the globe have developed numerous ways to “unfreeze” them, or to draw them out and amplify them.
Applying heat to most dried spices—a technique known as tempering—helps move these fragrances out of the spices, so that when they hit your tongue, they produce a stronger flavor experience. (We will get into this in a bit more detail later.) Heat can also transform some of the flavor molecules in spices into new, tastier ones—or it may reduce their harshness. (It also kicks out any moisture that might have accumulated over time during storage.) The end result is an amplified sensorial experience that would not otherwise be achieved in the absence of heat. Some cooks dry-toast spices; others pound whole spices with wet ingredients before warming them. But I’m most interested in tadka, so I looked into the physical and chemical reactions that occur when dried spices are tempered in hot oil.
What Is Tadka?
Simply described, tadka is a heat-based, flavor infusion technique that relies on fat as a flavor-delivery vehicle. Depending on the types of spices, herbs, and aromatic ingredients used, the fat extracts, sometimes alters, and subsequently delivers a combination of aromas, tastes, textures, color, and even sound to the dish. Some fats also carry their own flavor, which adds to the tadka experience.
As we’ll outline in more detail below, tadka (which is a noun and a verb in Hindi) is made when oil or a fat like ghee is heated in a pan, and dried spices (whole, crushed, or ground), other aromatics like garlic or fresh ginger, or leaves like those from a curry tree, are added and briefly warmed.
How to Use Tadka
Think of tadka as a layer of flavor. Often, it’s added as a garnish to a dish before serving. Tadka can be drizzled over the top of or be incorporated into dishes both hot—as in dals, sauteed vegetables, or meaty stews—and cold, such as raitas. South Indian coconut chutneys that are served warm or at room temperature are also often garnished with tadka.
Tadka may also be the foundation of a dish; when a tadka is prepared at the start, before you add other ingredients, I call it a “reverse tadka.” In the case of a reverse tadka, the cook is aiming to draw out the flavor molecules from the spices in the cooking oil, but then, as the dish cooks, those flavor molecules infuse into the rest of the components of the dish, including any vegetables, liquids, or proteins. (This is similar to how many soups, stocks, braises, and other dishes are made, in which aromatic vegetables are first sautéed and browned to build flavor at the start.)
A Tadka By Any Other Name
In many Asian countries, spices, especially chilies and peppercorns, are bloomed in hot oil. There are many names for this technique; for me, an Indian who grew up in Mumbai, it’s called tadka. But even within India, people speak nearly twenty-two different languages (in different scripts and dialects), so it’s not surprising that tadka goes by many names. My dad’s family is from the state of Uttar Pradesh, and mostly call it tadka and sometimes chaunk (also spelled chhonk). My maternal grandmother, who was from the West Coast of India, often called it phanna, as it is known in the Konkani language, and sometimes as baghar, which is another name for it in Hindi. Vaghar in Gujarati, phoron in Bengali, tarka in Urdu, oggarane in Kannada; these are just some of the other names for this technique and flavor layering element.
The Science of Tadka
There are three main players in the making of a tadka: heat, fat, and spices. But time and the right tools are also key to achieving a fragrant, well-developed tadka that is neither musty nor bitter. Here’s what you need to know.
One of the oldest methods of preserving food, including spices, is drying it at a low temperature. When spices are dried, the water is removed by evaporation, which helps to prevent the growth of microorganisms and slows down enzyme-based reactions. This process arrests the flavor molecules in spices, “freezing” them inside their cells, and preserves the quality of their flavor.
Much like when Han Solo is thawed out from a block of carbonite in Star Wars: The Empire Strikes Back, the flavor molecules in tadka can come back to life when they’re introduced to heat. When spices are heated, the heat provides energy—it makes molecules vibrate. First, the fat becomes more fluid as it gains the energy necessary to penetrate the dried spices, and then the flavor molecules inside the spices gain energy and dissolve in the hot fat quickly.
A cook will be able to tell when this chemical reaction has occurred because they’ll smell it: The flavor molecules will start to volatilize. Aromatic molecules are very small in mass, which is why they evaporate very quickly into the air, and heat speeds up their rate of evaporation.
Heat also promotes two flavor-producing reactions: caramelization and the Maillard reaction. When sugars are heated, they undergo a series of chemical reactions that result in browning and new flavor molecules, which we identify as caramelization. The Maillard reaction refers to a series of reactions that involve the amino acids present in proteins and certain sugars (reducing sugars like glucose and fructose), but it also leads to browning and the development of new flavor substances. These reactions happen in foods of all sizes, not just onions or large cuts of meat. Even the essential oils inside spices are transformed chemically through oxidation during heating. The combined effect of these different transformations helps change the flavor profile of each of the individual ingredients in a tadka.
Below I'll review all of the possible and mostly traditional ingredients that can go into a tadka. This list is organized, in general, by the order in which you would add the ingredient to the pot. There are many potential exceptions, which I also note below.
Because most of the flavor molecules in spices are fat-soluble, they can be easily extracted using fat. Fat also helps pull out color from spices; the pigments present in turmeric and red chilies are fat-soluble and the fat will quickly take on their color. This may add visual interest to a finished dish, in addition to flavor.
When it comes to the choice of fat, there are numerous options. Using fresh oil is important.* In India, many of these options are tied to what’s available locally. For example, recipes from the Southern coastal regions of India will use coconut oil; while in the North, mustard oil and ghee are more popular.
Fats that carry distinct flavors, like ghee, coconut oil, sesame oil (and gingelly, which is a type of sesame oil used in India that has a darker golden color), and mustard oil, and neutral oils, like peanut, grapeseed, canola, or safflower, are all great options. While not a traditional option by any means, I’ve used extra-virgin olive oil and it works well in dishes that are served warm.
*If you use an old, rancid bottle of oil to make tadka, your tadka will taste rancid.
A few things to keep in mind when choosing a fat for a tadka:
- Do you want to use a fat with a unique flavor like coconut or mustard oil, or a neutral oil like grapeseed? For example, the aroma of coconut oil will enhance the flavor of a coconut chutney, but might be distracting or compete with other flavors in a dish like raan, a spiced roasted leg of lamb, or a biryani.
- Is your dish served warm or cold? If your dish is served chilled, like a raita, avoid using fats like ghee and coconut oil because they will congeal and harden as soon as they meet cold temperatures. (Even some brands of olive oil may do this, depending on how many free fatty acids they contain at the time of extraction; the more free fatty acids an oil contains, the more likely it is to solidify at cold temperatures.)
- Check the smoke point of the oil you plan to use. When I prepare a tadka at home, I typically heat the oil to between 325°F (163°C) and 350°F (180°C), so I make sure the oil I use has a smoke point that’s higher than this range. Though this is not necessary, and in fact may hinder your cooking process, oil temperature can be measured using an infra-red thermometer. (See: how to use spice seeds as a tool for temperature, below.)
Note: If the fat is too hot or the spices are left for too long in the hot fat, they will burn, and the tadka will be bitter. If that happens, you will need to discard the burnt tadka, and start fresh.
Spices and Other Flavorings
While fat is the delivery vehicle and, in some instances, provides its own layer of flavor, it's the combination of spices used that makes each tadka unique. Tadka is dictated as much by recipe as by personal preference; every home has their own favorite combination of spices that they like to use, and some tadka formulas work better for some dishes than others. Two notes on spices and fresh ingredients:
- Whole spice seeds like cumin and coriander, and some legumes (such as urad beans and peas like split pigeon peas or toor dal) add texture and can be used directly, but they can also be lightly cracked to help the oil penetrate and dissolve the flavor substances inside their shells.
- Grinding a spice breaks it down into many individual smaller particles, thereby increasing its exposed surface area. Consequently, ground spices will cook faster, and release their flavor molecules more quickly than when cooked in their whole form. Besides spices, ingredients like onions, garlic, and tomatoes are also added to some tadkas for texture and flavor. (Note that fresh ingredients will add moisture to the hot fat, and may cause sputtering.)
By no means is this a complete list of all the spices and ingredients that can be used to build flavor in a tadka, but my goal here is to give you a sense of what the most common ingredients are, what they do, how to use them, and the order in which you would add them to the hot oil.
Whole, Dried Spices, Seeds, and Small Beans
Coriander, Cumin, Fennel, Fenugreek, Nigella, or Sesame Seeds: Crunchy and aromatic, when these seeds are added to hot oil, they sizzle and pop. This is the easiest way to ascertain how hot the fat is without using a thermometer. Add one or two seeds (mustard seeds, see below, also work) to the hot fat, and if it sizzles, the fat is ready. Once the seeds stop sizzling and turn brown, it’s time to add the next ingredient, or remove the tadka from the stove.
Mustard Seeds: Small and round, mustard seeds belong to the family of plants that include cabbages, and leave a wasabi-like sensation on the tongue. In Indian cooking, black and brown mustard seeds can be used interchangeably, but white or yellow mustard seeds are not usually used, as they have a weaker flavor in comparison. (This is because the latter produces a different type of chemical substance: sinigrin in black and brown mustard seeds gives the spice a more pronounced heat, and sinalbin in white mustard seeds gives a significantly milder dose of heat.) They also add a nutty aroma to the oil along with texture.
Green and Black Cardamom Pods: These pods must be cracked lightly, in a mortar with a pestle, for example, before they are added to the hot fat.
Cinnamon: Cinnamon sticks give a warm and sweet aroma to hot oil. In Indian cooking, cinnamon usually refers to the cassia bark, but you can use true cinnamon if you have that on hand. Their aromas are slightly different; I find the latter to be a bit more floral. Ground cinnamon can also be used in a tadka, though it will give a more intense flavor. (I use 1/2 teaspoon ground cinnamon for every 1-inch [2.5-cm] piece of cinnamon stick.)
Turmeric: This root contains the fat-soluble pigment curcumin, which will turn oil a bright yellow-orange. For the most part, ground turmeric is used in tadkas; however, you can cut fresh turmeric into thin strips and add it to the hot oil like ginger. Heat also helps mellow the pungency of raw turmeric.
Lentils and Some Beans Split-pigeon peas and hulled urad dal (vigna mungo) are added to tadkas, especially in South Indian cooking, and used to garnish coconut chutneys. A teaspoon or two of dried uncooked lentils will be rendered crunchy, and will impart a nutty aroma to the oil.
Asafetida: Also called hing in Hindi, this is the dried latex obtained from the root of the Ferula plant. It's sold as a ground powder with a slight yellow tinge that develops as it ages in storage. When raw, it carries a smell that some find unpleasant, but when heated in hot fat, it undergoes a chemical transformation and produces an aroma that's very similar to garlic and onions. Though they're from different plant families, asafetida and alliums contain certain types of sulfides that give them their unique aromas. Some communities in India that do not consume garlic or onions take advantage of this property, and use asafetida as a substitute to recreate that onion flavor. A tiny pinch goes a long way. Add asafetida after adding whole spices to a tadka, as the oily resin needs ample time to reveal its aromatic character.
Onions and Shallots: When thinly sliced and added to the hot fat, these alliums add their fragrance and flavor to the finished tadka. Depending on how long you cook them and how thinly you slice them, they will turn crispy or remain tender. The sugars inside these vegetables also undergo caramelization and the Maillard reaction to produce bittersweet-tasting substances and toffee-colored pigments. Both work well, though I prefer shallots due to their smaller size.
Ginger: Whether cut into thin, fine strips, minced, or grated, ginger adds a fresh and energizing aroma to tadkas. Fresh ginger gets its heat from gingerol, which is fat-soluble. Add ginger carefully, as it has a large quantity of water inside that can spurt and sputter as it meets the hot fat. Keep in mind that the thicker the cut of ginger, the longer it will take to cook. I add julienned ginger to the fat after I add the whole seed spices, since it takes a little more time to cook than other aromatic ingredients, but smaller cuts or grated ginger after adding most of the other ingredients, so it does not overcook.
Chilies: Chilies contribute two important substances to tadkas: capsaicin, the substance that works by “irritating” specialized nerve receptors that sense heat and pain—a phenomenon called chemesthesis—which we’ve evolved to find pleasurable, and, in the case of dried chilies, the bright red carotenoid pigments, like capsanthin, which tinge the oil red.
While researching my new book, I learned that capsaicin can do one more thing when it’s added to hot oleic acid—a fatty acid that’s present in high quantities in ghee and grapeseed and olive oil: it can decompose and produce two new substances that act as antioxidants and protect the oleic acid from degradation. Essentially, it can slow the rate at which a fat oxidizes, thereby inhibiting rancidity.
Both fresh and dried chilies can be used in a tadka. The trick is to cut the chilies to allow the hot oil to come into contact with the heat-producing capsaicin concentrated within the thin membrane that lines the pepper's center cavity and the seeds. Fresh chilies can be cut in half across their length or chopped into thin slices and added to the hot fat. If you use whole, dried chilies, you can break the stalk off or leave it, but I recommend tearing or cutting the chili so the hot oil can reach inside and extract those flavor substances.
Dried Kashmiri chilies are often used for their milder heat and bright color, but hotter dried chilies can also be used in a tadka. While a bit unconventional, I like to use chili flakes from Aleppo or Maras peppers for their bright color and aroma. Dried chilies can burn faster than fresh chilies, so add them toward the end of cooking the tadka, and if you use chili flakes or ground chilies, I recommend adding them as soon as you take the oil off the heat. The heat from the hot fat will continue to extract the flavors from the chili flakes without the risk of scorching them.
Curry Leaves: Prized for their unique aroma and the crunchy texture of their leaves as they crisp up in the hot fat, curry leaves are more popular in South Indian cooking, and in recipes from the warmer coastal states of India where the plant grows. When I cook with curry leaves, I rinse them under cold running tap water and then pat them dry with a clean towel to remove any excess water. It’s a good idea to rub the leaves gently between your palms to bruise them before adding them to the hot fat—this additional step ensures their flavor will be fully released into the oil.
I prefer fresh curry leaves to dried ones because they have a stronger aroma, but when I add them to the hot oil, I immediately cover the saucepan with a lid because the moisture in the leaves can cause the oil to sputter. Fresh leaves have a more pronounced flavor than dry, so if you're substituting dried curry leaves for fresh, you'll need to double or triple the quantity of leaves.
Bay Leaves: Fresh or dried Indian bay leaves (tejpatta in Hindi) can be added to the hot fat to impart a cinnamon-like aroma. Sweet European bay leaves can be used in a pinch, but they look different and taste more herbaceous.
Garlic: Fresh garlic is sometimes added to tadka. The chemicals responsible for the heat and aroma in garlic are fat-soluble, so they dissolve in the hot fat. Garlic burns easily; I recommend adding it just before finishing a tadka, after dry spices are added, so that it doesn’t burn and become bitter. I’m often asked if garlic is necessary in a tadka, and the short answer is no: There are plenty of tadkas that don't use garlic. (See: asafetida)
Tools for Making Tadka
Because seeds can sputter and fly out, and fresh herbs like curry leaves and even green chilies contain water that will crackle in the hot oil, I prefer to use a small saucepan with deep sides and a lid when I make a tadka.
You can grind whole spices down with a mortar and pestle or use a heavy object like a rolling pin or cast iron pan. Chilies can be cut using a knife or a pair of kitchen shears.
I typically do not use a spoon to mix the spices once they’re added to hot oil; instead I gently swirl the contents of the saucepan to disperse the spices and prevent them from sticking to the bottom. Once the tadka is complete, you can pour the hot oil with the spices directly over the dish or use a dry metal spoon to spoon it out and onto the dish.
How to Make Tadka
In general, it takes just around a minute for the spices in a tadka to brown, sizzle, and release their fragrance. Use all of your senses, especially sight, sound, and smell, to assess a tadka’s development. I find the sound and visual cues to be much more useful guides than a precise measurement of time or temperature.
Whole spices will stop sizzling and sputtering when they’ve released all of their moisture and flavor, and they will turn light to toffee brown—don't let them get too dark or they will taste bitter. Curry leaves, when completely cooked, will be crisp and somewhat translucent.
While every tadka is unique, here is a rough guide to how I approach making it; other cooks may have slightly different methods. Generally speaking, the process is as follows:
- Heat the oil in a small saucepan over a medium or medium-low flame. Test the temperature of the oil to make sure it is hot enough by dropping in one or two whole spice seeds (based on what you’re using) such as cumin, coriander, or mustard. The spices will sizzle immediately if the oil is sufficiently hot.
- Add the rest of the whole spices, including larger pieces like cinnamon sticks, and small beans or lentils.
- If using onions, shallots, and ginger, and if you want them browned and crisp, add them now.
- If using asafetida (hing) or other ground spices, add them next. They will be fragrant and lightly toasted within a few seconds.
- Dried chilies can burn easily so, to reduce the risk, I add whole dried chilies after adding the ground spices.
- If using fresh green chili, add it here, but take care as it may cause the oil to sputter. If using onions, shallots, and ginger, and you do not want them browned or crisp and want to retain a fresher flavor, add them now. This is also a good moment to add curry leaves or bay leaves
- If using garlic, add it now, because garlic cooks very quickly.
- At this point, remove the saucepan from the stove and, if using, add ground chili powder or chili flakes. The residual heat is enough to extract their flavor.
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