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We all knead flour at home to make rotis or chappatis. It seems like such a routine activity that we dont consider it to be a chemical reaction anymore. We have noticed before that when dough is kneaded too long it becomes elastic, we always rest the dough for sometime before using it, why do we follow these steps ?
Here is an attempt to answer these questions. We start with a simple dough that is made by kneading wheat flour with water and go on to understand how yeast acts on dough to give us the delicious bread we eat everyday.
When flour is mixed with water the proteins present in flour – Glutenin & Gliadin, grab water and each other to form an elastic mass of molecules called ‘Gluten’.
The more you knead the dough stronger the gluten bonds become.
Let the dough rest for sometime before making bread or
rolling it out into rotis/chappati
When the dough is allowed to rest the gluten bonds relax
making it easier to give shape to the dough.
Leavening is the process of adding gas to a dough before baking to produce a bread that is light and easy to chew.
Stir yeast with sugar in warm water until it
dissolves.
Yeast cells feed on sugar and get activated.
Yeast metabolizes sugar to produce CO2 and
ethanol.
Warm water is used because optimal temperature for yeast to ferment sugar is 32 ° C.
The yeast mixture is now kneaded with flour to prepare a dough
Kneading helps distribute the yeast evenly
throughout the dough hence strengthening the
gluten bonds.
The more the dough is worked upon, the chewier the end product will be. This would be desirable for bakes like bagels, pizza crust or French bread.
Bread that has not been kneaded enough tends to be crumbly and falls apart easily due to weak gluten bonds.
The by-product ‘Ethanol’ is an alcohol that contributes to the bread’s flavor.
The dough is now allowed to rest. In about an hours time it doubles up in volume.
If the dough has a strong gluten network the produced CO2 is trapped in the dough in the form of tiny bubbles and the dough begins to inflate.
Each Co2 bubble helps more protein find water, hence forming more gluten. Its almost like kneading at the molecule level resulting in a stronger gluten network.
The dough is now punched down and kneaded further with light hands
Punching down the dough releases the large
CO2 bubbles. If the gas is not allowed to
escape you will end up with yeasty flavored
bread! Kneading further causes the gluten
bonds to strengthen.
Now allow it to rest for a short while so that the gluten bonds relax and it will be easier to shape the bread.
Give the desired shape to the dough and
let it rest for a short while till it puffs up.
This is to complete any yeast activity
before the dough goes into the oven.
Once in the oven, yeast will become
completely inactive as yeast cells die at
around 45 °C.
The enzymes in the flour that were assisting the break down of starch also become inactive now.
Once the bread is done you can tap the bottom of the bread can. If it sounds hollow the bread is ready, else it needs to be baked further.
Certain breads appear more brown on baking than others. There are a couple of reasons behind that :
1) Wheat flour breads are naturally browner than breads made with white flour.
2) If milk was used in the dough you will get a browner bread. Milk contains lactose, a sugar that yeast can not act on. Hence, lactose is available for browning. The color change starts when its heated to about 175 °C.
Dough that doesn’t contain milk can be refrigerated up to 3 days. However, if it has milk then its shelf life is reduced to 2 days.
There is another case of bread making where you intentionally refrigerate the dough and bake it later as the bread seems to have a better flavor this way.
The reason behind this change of taste is that at low temperatures bacteria begins to act on the dough. Yeast does not die at low temperatures, rather its activity reduces giving bacteria a chance to feed on the sugar and produce flavorful acids. This process of bread making is also known as ‘Cool Rise’.
If the dough is stored for too long the CO2 released by slow yeast action, along with the acids produced by bacteria will cause the dough to turn sour.
Nice writeup. Enjoyed reading it. These type of what-is-behind kind posts are refreshing to read apart from the recipes. Good job.
great info very intresting and helpfull
nice writeup… loved the chemistry twist to it… makes an interesting read…
This is a neat post, Roma!! I read all about this from here and there but to see it all in one post is great!
Very good post! So useful.
veru useful post..never thought what actually happens during bread making until I read this post ..
Wonderful post!!! Atleast someone thought of putting some logic into things that we’ve been doing since ages and didn’t bother to think why.. Awesome post..Thanks for putting this together for us..:)
Lovely post Roma..Loved reading the chemistry. It is useful and interesting to know the mechanism behind cooking/baking.
My sis will love to read this,she is a post graduate in chemistry ,but i am not sure whether she had LOOKED dough or bread with this perspective
Lovely informative post:-)
very nice post – informative without completely going over my head – thanks to the gfx~!!!good job and thanks!
very informative write up … bread making simplified..
Great post! Kneading is also a stress buster!! But I use my KitchenAid! 😀
That was a very good post…things we always overlook while we go about performing the routine steps, well presented!
Well done Roma!… Think this is the best post on food I have read in a long time.. informative and explanatory with pictures like an easy to read story book 🙂
Dear All,
Thanks so much for your comments. Do remember me (and the bacteria cartoon :)) when you make bread next.
Cheers,
Roma
Hi..Great post..Thank you..
Very interesting n informative..loved the explanation with pictures..
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Lovely…nice to read
Lovely write-up Roma..never knew all these things happen wth our humble chapathi dough;-)
Very informative post Roma, was a very interesting read 🙂
There’s a Malay dish that i want to share with you. Hope that you can have a look at this and let me know what you thing of it yea?
http://icedlemontea.wordpress.com/2009/01/17/ayam-masak-merah-chicken-with-chilli-paste/
You did a wonderful job at breaking down the bread making steps Roma. I thought I was watching Alton Brown on Good eats 😀 My first few attempts at making bread failed miserably and only after I had read the process behind did I get decent quality ones. Its so much fun knowing all these too 🙂
Wow…thats a wonderful post. Very informative, I had no idea about all the logic behind making a dough. This is really helpful.
That’s an awesome post… fun to read 🙂
A very nice way to describe the bread making chemistry 🙂
Excellent quality of information, easy reading. Can you also clarify the use of vinegar in puff pastries? Does is help the gluten development?
Vinegar being acidic in nature helps in relaxing the gluten, hence making it easier to roll out the dough.
I LOVE YOU! You saved my chemistry project! I LOVE BREAD!
Love this but will like you to explain the process of making other flour foods