Discovered by accident thousands of years ago, yogurt has become a staple in home cooking. A quick and calcium-filled snack for a hungry kid or a healthy means of adding a creamy taste to baking and cooking, the fermented milk product has a variety of uses. However, when attempting to make a yogurt-based sauce or a simple curry, yogurt's creamy texture often breaks, leaving a curdled mess. A few simple techniques can prevent this devastation and result in a break-free and smooth sauce.
Adding acidic ingredients like lemon juice, vinegar and even fruits can curdle both milk and yogurt. Using whole-fat yogurts reduces the curdling effect, and cooking at a low temperature can offset the effects of acid. However, the best way to keep a yogurt-based food from curdling is by omitting acids or substituting them for milder, more pH-neutral ones. Serve acid-based compotes or chutneys on the side, for instance, instead of stirring them into yogurt during a recipe's cooking process.
Heat is one of the main reasons for yogurt curdling. To maintain the smooth texture of yogurt while cooking, add the yogurt at the end of the dish's cooking time; avoid bringing the dish to a boil, and remove the dish from the heat, then stir in the yogurt.
Using a stabilizer in a yogurt-based dish to keep it from curdling is one of the most common steps in Indian cooking. Whisk in a small amount of chickpea flour, cornstarch, or plain all-purpose flour to stabilize the yogurt before cooking. Ensure that the stabilizer is completely combined, then add the combination slowly to a low-temperature dish, or heat the stabilizer slowly on its own, again keeping it from boiling, and stirring it in at the end of the preparation.
The type of yogurt plays a large part in whether it will curdle. Buffalo-milk yogurt is less prone to curdling overall, and is commonly used by traditional Indian cooks. However, if this is unavailable, substitute full-fat yogurt, or Greek yogurt, where much of the water has been removed; both are less likely to break than low-fat yogurt, because the fat within the yogurt keeps proteins from clumping together and curdling. If you want to use low-fat products, only use a small amount of acid in the recipe, use a stabilizer in the yogurt and cook on low heat to prevent curdling.