Engineering behind Daily life

Engineering behind "Chapati"

How does Chapati inflate like balloon?


Question is that how does a chapati separate into 2 layers and inflate like balloon when cooked.


The uncooked dough is composed of 3 components.
1. Water
2. Flour
3. Trapped air bubbles

The flour being a complex carbohydrate is hydrolyzed by water and hence form long molecular chains that cling with each other, thereby giving a sticky plastic dough.
These molecular chains form an air proof matrix. Hence no air bubbles can escape out, without breaking the surface of the dough.
Now since you understand the chemistry part of the reaction, let us look at the physics of the phenomenon. Let us see how a good chapati is cooked.
  • Step 1: Press the dough by a "roller" (sorry couldn't find a better word for Belan) to make it a flat round slice.
  • Step 2: Place the slice on the tawa (flat pan) and heat it till one face slightly dries by heat.
  • Step 3: Turnover the slice on the tawa, such that other side of the slice becomes more dry. This side should be heated more than the previous side.  Hence it becomes drier compared to other side.
  • Step 4: Place the less cooked side of the chapati on open fire. The chapati will inflate like a balloon

This is the key to the inflating of the chapati. Since one side is more dry compared to other side. Hence there is difference in the density of the two sides which is responsible for their division. The intersection of the two sides is the layer which splits up, forming the two layers of chapati. 

On heating up, the air bubbles trapped inside the dough and the water convert into steam, expand and create an inflationary force. The more dry layer is able to escape from the hydrophilic bond of the moist layer when the air expands it.

So you see, this is the key to making a good chapati. Cook one side more than the other.

 About Chapati :


Chapati (alternatively spelled chapatti, chappati, chapathi, or chappathi), also known as roti, safati, shabaati, phulka and (in the Maldives) roshi,[1] is an unleavened flatbread from the Indian Subcontinent and staple in India, Nepal, Bangladesh, Pakistan, Sri Lanka, East Africa and the Caribbean.[2] Chapatis are made of whole wheat flour known as atta, mixed into dough with water and optional salt in a mixing utensil called a parat, and is cooked on a tava (flat skillet).[3][4]
It is a common staple in the Indian subcontinent as well as amongst expatriates from the Indian subcontinent throughout the world. Chapatis were also introduced to other parts of the world by immigrants from the Indian subcontinent, particularly by Indian merchants to Central Asia, Southeast Asia, East Africa, and the Caribbean islands.[5]

History

The word chapat (Hindi:चपत) means "slap","flat" which describes the traditional method of forming rounds of thin dough by slapping the dough between the wetted palms of the hands. With each slap, the round of dough is rotated. Chapati is noted in the 16th-century document Ain-i-Akbari by Abu'l-Fazl ibn Mubarak, vizier of Mughal Emperor Akbar.[2]
Chapatis are one of the most common forms of wheat bread which is staple food in the Indian subcontinent. The carbonized wheat grains discovered at the excavations at Mohenjo-daro are of a similar variety to an endemic species of wheat still to be found in India today. The Indus valley is known to be one of the ancestral lands of cultivated wheat. Chapati is a form of roti or rotta (bread). The words are often used interchangeably.
Chapatis, along with rotis, were introduced to other parts of the world by immigrants from the Indian subcontinent, particularly by Indian merchants who settled in Central Asia, Southeast Asia, and the Caribbean islands.[5]

Cooking

Chapatis are made using a soft dough comprising atta flour, salt and water. Atta is made from hard gehun (Indian wheat, or durum).[6] It is more finely ground than most western-style whole wheat flours. Traditionally, roti (and rice) are prepared without salt to provide a bland background for spiced dishes.[7]
Chapati dough is typically prepared with atta, salt and water, kneaded with the knuckles of the handmade into a fist and left to proof for at least 10 or 15 minutes to an hour for the gluten in the dough to develop. After proofing, the dough becomes softer and more pliable. Small portions of the dough are pinched off and formed into round balls that are pressed between the two palms to form discs which are then dipped into flour and rolled out on a circular rolling board (a chakla), using a rolling pin known as a velan or belan, into a perfect circle. There are also automatic roti makers like Rotimatic available that automate the whole process.

The rolled-out dough is then thrown on the preheated dry tava and cooked on both sides. In some regions of the Indian subcontinent chapatis are only partially cooked on the skillet, and then put directly on a high flame, which makes them blow up like a balloon. The hot air cooks the chapati rapidly from the inside. In some parts of northern India and eastern Pakistan, this is called a phulka. In southern parts of India, it is called a pulka. It is also possible to puff up the roti directly on the tava.Once cooked, chapatis are often topped with butter or ghee.

Chapati diameter and thickness vary from region to region. Chapatis made in domestic kitchens are usually not larger than 15 centimetres (6 in) to 18 centimetres (7 in) in diameter since the tava on which they are made comes in sizes that fit comfortably on a domestic stovetop. Tavas were traditionally made of unglazed earthenware, but are now typically made from metal. The shape of the rolling pin also varies from region to region. Some households simply use a kitchen worktop as a sort of pastry board, but round flat-topped "boards" made of wood, stone, or stainless steel are available specifically for rolling out chapatis.

In most parts of the Indian subcontinent, there is a distinction made between a chapati and other related flatbreads eaten in the region like roti, paratha, kulcha, puri and naan based on cooking technique, texture and use of different types of flours. For example, parathas are either made layered by spreading with ghee, folding and rolling out again into a disc which turns out flakey once cooked or is filled with spinach, dal or cooked radish or potato. Parathas are mostly made using all-purpose flour instead of whole wheat flour.
There are many regional varieties of chapati in India.
  • Paneer chapati: Grated paneer is added to the usual chapati dough
  • Radish or mullangi chapati: Grated radish and turmeric powder is added to the dough and the chapati is usually thick. It is often eaten by lorry drivers who eat in roadside dhabas during long trips.
  • Vegetable-stuffed chapati: Mashed carrot, potato, peas, and fenugreek are slightly sauted into a masala gravy. These chapatis are usually served rolled, and many households prepare them using their own combinations of available vegetables.
In the Maldives, chapatis are traditionally eaten for breakfast along with a dish known as mas huni.
 
 
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