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 households for centuries. The crispy exterior and soft interior of a perfectly cooked dosa is a delight to the senses. However, have you ever wondered what makes a dosa crispy on the outside and soft on the inside? A professor from IIT-Madras, Prof Mahesh Panchagnula, has shed some light on this phenomenon, and it’s fascinating.
According to Prof Panchagnula, the secret to a crispy dosa lies in the way it’s cooked on the tawa. Specifically, the practice of sprinkling water on the hot tawa before pouring the dosa batter is linked to a fascinating scientific concept known as the Leidenfrost Effect. This phenomenon was first identified in Germany in the 18th century by Johann Leidenfrost, a German physician and theologian.
So, what is the Leidenfrost Effect? In simple terms, it’s 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 on the surface vaporize rapidly, creating a thin layer of vapor between the liquid and the surface. This vapor layer reduces the heat transfer between the surface and the liquid, allowing the liquid to glide and float on the surface without coming into direct contact with it.
Now, let’s apply this concept to cooking dosas. When you sprinkle water on a hot tawa, the water droplets vaporize rapidly, creating a thin layer of vapor between the tawa and the dosa batter. This vapor layer prevents the dosa batter from sticking to the tawa, allowing it to cook evenly and crisp up on the outside. However, if the tawa isn’t hot enough, the water evaporates slowly, and the dosa batter sticks to the surface, resulting in a soggy or undercooked dosa.
The Leidenfrost Effect also explains why dosas are soft on the inside. When the dosa batter is poured onto the hot tawa, the vapor layer created by the water droplets helps to cook the batter evenly and quickly. The heat from the tawa is transferred to the batter through the vapor layer, cooking the exterior rapidly while keeping the interior soft and fluffy.
In addition to the Leidenfrost Effect, there are other factors that contribute to the crispy exterior and soft interior of a dosa. The type of rice and lentils used to make the dosa batter, the proportion of ingredients, and the fermentation process all play a crucial role in determining the texture and flavor of the dosa.
The fermentation process, in particular, is critical in creating the soft and fluffy interior of a dosa. During fermentation, the starches in the rice and lentils are broken down, producing lactic acid and carbon dioxide gas. The carbon dioxide gas gets trapped in the batter, creating a light and airy texture that is characteristic of a well-made dosa.
In conclusion, the combination of the Leidenfrost Effect and the fermentation process are the key factors that make dosas crispy on the outside and soft on the inside. The next time you cook a dosa, remember the science behind this delicious dish, and appreciate the complexity and beauty of the culinary process.
This fascinating explanation by Prof Mahesh Panchagnula has shed new light on the art of cooking dosas, and we’re sure that dosa enthusiasts will appreciate the science behind this beloved dish.
News Source: https://x.com/iitmadras/status/1993901259925909929
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