rice curling and bursting

[Zulfiqar Ali]

Dear guys,
What is the reason of bursting and curling or rice after boiling them?

Thanks,

Rgrds,
Zulfiqar

[Judy Sebastian]

Dear Mr. Zulfiqar,
Hello.

To understand what really happens when rice grains swell and burst or curl
after they have been cooked, you would have to go down to the molecular and
sub molecular level.

Rice is rich in starch and starch is made of linked sugar molecules namely
amylose and amylopectin. Amylose is comparatively smaller in size and both
these molecules are arranged like little stacks within the grain.

As the temperature of the water increases during the cooking process, the
starch molecules become more and more soluble -that is, they begin to
partially dissolve in water. This process is known as gelatinization.

During gelatinization, the amylose and amylopectin molecule disperse
themselves kind of like disturbing an ant trail - they scatter across.
The rice grain begins to absorb water because the amylose leaches out and
tries to lock the water in. This is what gives the cooked rice a somewhat
'burst open' look .
Also, you'll notice that cooked rice has greater volume as well because of
the water that has been absorbed.

Different varieties of rice have different starch levels and the way you
cook them too, affects the final appearance / texture.

Hope I've clarified your query.


Thank you
Warm regards,
Judy



E: ju...@apexfoodconsultants.com | W: www.apexfoodconsultants.com

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[Preveen Kumar]

Hello,

I have attached 2 images along with the mail. I believe this might give a pictorial understanding of the process "how a starch molecule dissolves in water". 

Image 1 - Amylopectin is the brach like structure and amylose is like a long thread like structure entangled in between the amylopectin branches as shown in the images above.

The second image shows the different stages by which a starch molecules dissolves in water. The process has been beautifully explained my Ms. Judi in her previous mail.

Regards

Preveen

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From: ju...@apexfoodconsultants.com
To: za....@yahoo.com; bkth...@dm.gov.ae; foodsaf...@googlegroups.com
Subject: RE: {Dubai's Food Safety Clinic} rice curling and bursting
Date: Wed, 22 May 2013 20:34:42 +0400

Dear Mr. Zulfiqar,

Hello.

 

To understand what really happens when rice grains swell and burst or curl after they have been cooked, you would have to go down to the molecular and sub molecular level.

 

Rice is rich in starch and starch is made of linked sugar molecules namely amylose and amylopectin. Amylose is comparatively smaller in size and both these molecules are arranged like little stacks within the grain.

 

As the temperature of the water increases during the cooking process, the starch molecules become more and more soluble -that is, they begin to partially dissolve in water. This process is known as gelatinization.

 

During gelatinization, the amylose and amylopectin molecule disperse themselves kind of like disturbing an ant trail – they scatter across.

The rice grain begins to absorb water because the amylose leaches out and tries to lock the water in. This is what gives the cooked rice a somewhat ‘burst open’ look .

Also, you’ll notice that cooked rice has greater volume as well because of the water that has been absorbed.

 

Different varieties of rice have different starch levels and the way you cook them too, affects the final appearance / texture.

 

Hope I’ve clarified your query.

 

 

Thank you

Warm regards,

Judy