IIT-Madras professor explains why dosas are crispy on outside & soft on inside
Dosa, a traditional Indian dish, has been a staple in many households for centuries. The crispy exterior and soft interior of a perfectly made dosa is a delight to the senses. But 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 explained the science behind this phenomenon, and it’s fascinating.
According to Prof Panchagnula, the practice of sprinkling water on a hot tawa before pouring the dosa batter is linked to the Leidenfrost Effect, a phenomenon identified in Germany in the 18th century. The Leidenfrost Effect is a physical phenomenon in which a liquid, in close contact with a surface significantly hotter than the liquid’s boiling point, produces a vapor layer that prevents the liquid from coming into direct contact with the surface. This effect is responsible for the crispy exterior and soft interior of a dosa.
When a tawa is heated to the right temperature, the water sprinkled on it does not evaporate immediately. Instead, it glides and floats on a thin vapor layer, creating a non-stick surface. This is because the vapor layer acts as a barrier between the dosa batter and the tawa, preventing the dosa from sticking to the surface. As the dosa cooks, the vapor layer helps to distribute the heat evenly, resulting in a crispy exterior.
On the other hand, when the tawa is not hot enough, the water evaporates slowly, and the dosa batter comes into direct contact with the surface. This results in a dosa that is sticky and soft on the outside, rather than crispy. Therefore, the key to making a crispy dosa is to heat the tawa to the right temperature, so that the water sprinkled on it creates a vapor layer that prevents the dosa from sticking.
But why does the dosa remain soft on the inside? The answer lies in the way the dosa batter is cooked. When the dosa batter is poured onto the hot tawa, it starts to cook immediately. The heat from the tawa causes the starches in the batter to gelatinize, resulting in a soft and fluffy interior. At the same time, the vapor layer created by the Leidenfrost Effect helps to retain the moisture in the dosa, keeping it soft and tender on the inside.
In addition to the Leidenfrost Effect, the type of batter used to make the dosa also plays a crucial role in determining its texture. The traditional dosa batter is made from a combination of rice and lentils, which are soaked, ground, and fermented to create a natural yeast. The fermentation process helps to break down the starches in the rice and lentils, resulting in a batter that is light and airy. When cooked, this batter produces a dosa that is crispy on the outside and soft on the inside.
In conclusion, the science behind a crispy dosa is fascinating. The Leidenfrost Effect, a phenomenon identified in Germany in the 18th century, plays a crucial role in creating the crispy exterior and soft interior of a dosa. By heating the tawa to the right temperature and using the right type of batter, one can create a dosa that is crispy on the outside and soft on the inside. Whether you are a foodie or a scientist, the next time you eat a dosa, remember the science behind its crispy exterior and soft interior.
This explanation by Prof Mahesh Panchagnula has shed new light on the traditional Indian dish, and it’s a reminder that there’s always more to learn about the food we eat. So, the next time you’re cooking dosas, make sure to sprinkle some water on the hot tawa before pouring the batter, and enjoy the crispy exterior and soft interior of a perfectly made dosa.
News Source: https://x.com/iitmadras/status/1993901259925909929
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