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 fascinated food enthusiasts and scientists alike. Recently, Prof Mahesh Panchagnula from IIT-Madras shed light on the science behind this phenomenon, and it’s more interesting than you might think.
For those who are unfamiliar, dosas are made from a fermented batter of rice and lentils, which is then poured onto a hot tawa (griddle) to cook. The practice of sprinkling water on the hot tawa before pouring the dosa batter is a common one, and it’s this step that holds the key to achieving the perfect dosa texture. According to Prof Panchagnula, this practice is linked to the Leidenfrost Effect, a phenomenon that was first identified in Germany in the 18th century.
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 evaporates rapidly, creating a thin layer of vapor between the water droplets and the hot surface. This vapor layer reduces the heat transfer between the water and the surface, allowing the water to “float” on the surface rather than coming into direct contact with it.
Now, let’s apply this concept to the process of making dosas. When the tawa is not hot enough, the water sprinkled on it evaporates slowly, and the dosa batter comes into direct contact with the surface. This can cause the dosa to stick to the tawa, resulting in a suboptimal texture. However, when the tawa is heated to the right temperature, the water sprinkled on it creates a thin vapor layer, allowing the dosa batter to glide and float on the surface. This prevents the dosa from sticking and helps to create a crispy exterior.
But how does this process contribute to the soft interior of the dosa? The answer lies in the way the heat is transferred to the dosa batter. When the dosa is cooking, the heat from the tawa is transferred to the batter through the vapor layer. This process, known as convective heat transfer, allows the batter to cook evenly and quickly, resulting in a soft and fluffy interior. The crispy exterior, on the other hand, is a result of the Maillard reaction, a chemical reaction between amino acids and reducing sugars that occurs when the batter is exposed to high temperatures.
The combination of the Leidenfrost Effect and convective heat transfer is what makes the perfect dosa possible. By sprinkling water on the hot tawa, the dosa batter is able to cook evenly and quickly, resulting in a crispy exterior and a soft interior. This is a testament to the ingenuity of traditional Indian cooking techniques, which have been perfected over centuries through trial and error.
In conclusion, the science behind the perfect dosa is more complex than one might think. The Leidenfrost Effect, convective heat transfer, and the Maillard reaction all play a role in creating the delicate balance of crispy exterior and soft interior that we associate with a well-made dosa. By understanding these principles, we can appreciate the art of traditional Indian cooking and the ingenuity of the people who developed these techniques.
The next time you enjoy a perfectly cooked dosa, remember the science behind it. The sprinkling of water on the hot tawa, the sizzling sound of the batter as it hits the surface, and the aroma of the crispy exterior all contribute to the sensory experience of eating a dosa. And now, thanks to Prof Panchagnula’s explanation, we have a deeper understanding of the science that makes it all possible.
News source: https://x.com/iitmadras/status/1993901259925909929
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