IIT-Madras professor explains why dosas are crispy on outside & soft on inside
Dosa, a traditional South Indian dish, has been a staple in many Indian households for centuries. The delicate balance of crispy exterior and soft interior has always been a topic of interest among food enthusiasts. Recently, Prof Mahesh Panchagnula from IIT-Madras shed some light on the science behind this phenomenon. In a fascinating explanation, he revealed that the secret to achieving the perfect dosa lies in the Leidenfrost Effect, a concept identified in Germany in the 18th century.
For those who are unfamiliar with the Leidenfrost Effect, it is a phenomenon where a liquid, in this case, water, comes into contact with a surface that is significantly hotter than its boiling point. When this happens, the water droplets do not immediately evaporate, but instead, create a thin layer of vapor between the liquid and the hot surface. This vapor layer reduces the heat transfer between the surface and the liquid, allowing the water to float on top of the vapor, rather than coming into direct contact with the hot surface.
Prof Panchagnula explained that the practice of sprinkling water on a hot tawa (griddle) before pouring the dosa batter is linked to the Leidenfrost Effect. When the tawa is not hot enough, the water evaporates slowly, and the dosa batter sticks to the surface. However, when the tawa is heated to the right temperature, the water glides and floats on a thin vapor layer, preventing the dosa from sticking and making it crisp.
To achieve the perfect dosa, the tawa needs to be heated to a temperature of around 200-250°C. At this temperature, the water droplets create a thin vapor layer, allowing the dosa batter to cook evenly and preventing it from sticking to the surface. The vapor layer also helps to cook the dosa batter quickly, resulting in a crispy exterior and a soft interior.
The Leidenfrost Effect is not limited to cooking dosas; it has many other practical applications. For example, it is used in heat transfer systems, where a thin layer of vapor is created to reduce the heat transfer between two surfaces. It is also used in the design of cooling systems, where a thin layer of vapor is created to increase the heat transfer between a surface and a fluid.
In addition to the Leidenfrost Effect, Prof Panchagnula also explained that the type of batter used to make dosas plays a crucial role in achieving the perfect texture. The batter should be made with a combination of rice and lentils, which provides the necessary structure and texture to the dosa. The ratio of rice to lentils, as well as the type of lentils used, can affect the final texture of the dosa.
The cooking time and temperature also play a crucial role in achieving the perfect dosa. The dosa should be cooked for a short period, typically around 1-2 minutes, to prevent it from becoming too crispy or too soft. The temperature of the tawa should also be adjusted to achieve the perfect cooking time.
In conclusion, the science behind the perfect dosa is fascinating, and it involves a combination of the Leidenfrost Effect, the type of batter used, and the cooking time and temperature. By understanding the science behind cooking dosas, we can appreciate the complexity and nuance involved in creating this simple yet delicious dish. Whether you are a seasoned chef or a novice cook, the next time you make dosas, remember the Leidenfrost Effect and the importance of achieving the perfect temperature and cooking time.
News Source: https://x.com/iitmadras/status/1993901259925909929
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