jueves, 31 de julio de 2014

Getting ahead in bread, and goopy gluten activity

 
 
  CSIRO   Lloyd's Register
1 AUGUST 2014
 
  Science by Email  
  
News: Getting ahead in bread    
   


Wheat is Australia’s main winter crop. Sown in autumn and harvested in spring or summer, it provides us with flour to make our daily bread. We eat wheat as toast with vegemite, or sandwiches for lunch. But wheat is not for everyone, as eating it can cause trouble for some people, such as those with celiac disease.
 

Songs and hymns have been sung for bread, yet even today it has its mysteries. Like all living things, it contains a genome – the collection of its genetic material, such as DNA. Scientists have found the DNA sequence for the genomes of humans, lions, tigers and bears. Oh my, but bread wheat is a whole other story.
 
“With bread wheat, it is a big challenge,” says Ute Baumann at the Australian Centre for Plant Functional Genomics. “Bread wheat has a genome more than five times larger than the human genome. It’s massive. Rice is tiny by comparison.”
 
Why so big? Today’s bread wheat came from three ancestor species, which combined thousands of years ago and shared their DNA. Each grain of wheat contains three sub-genomes from the three ancestor species.
 
In July, an international team of scientists announced that they had made a rough draft of the whole genome of bread wheat, and a detailed version of one single chromosome, 3B. A team in Australia is working now to create a detailed version of chromosome 7A. “There are a number of important traits on chromosome 7A,” says Ute. “It has genes involved in salt tolerance, yield and flour quality.”
 
The rough draft was made using a method called shotgun sequencing, which breaks the genome into small parts and then sequences them. It’s like a big jigsaw, and the trick is putting all the little pieces together. It’s very difficult, because the wheat genome is very repetitive and a lot of the pieces are the same.
 
A more detailed version, like the one Australian scientists are working on for chromosome 7A, uses a method called BAC by BAC sequencing. BAC stands for bacterial artificial chromosome, and this method cuts the DNA into much larger sections and grows them in bacteria. This method is slower, but makes it possible to piece the whole chromosome together.
 
With a map of wheat’s genome, it’s much faster for plant breeders to grow varieties of wheat that are more productive, or better suited to Australian conditions. As the world’s population grows bigger and bigger, better bread wheat needs to be on the menu.
 

More information

Wheat genome project.
Fiendish wheat genome reveals grain’s history.
How shotgun sequencing and BAC by BAC work.

 
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Image of bio-printed blood vessel

Scientists are shedding light on bread wheat's genome.
Image: © iStock.com/ithinksky

 
 
   
    Quiz questions    
   
  1. What kind of animal is a barbel?
  2. In rocket fuel, which liquid is known as LOX?
  3. How thick is the Earth’s crust? Is it approximately a) 40 kilometres, b) 400 kilometres or c) 4000 kilometres?
  4. True or false? Red blood cells are larger than liver cells.
  5. What force, starting with d, is created by parachutes to slow objects down?
   
Sci-ku competition  
 
 
 
Sci-ku competition
 
 
   
   

Can you Sci-ku? Get involved in the RiAus Sci-ku competition for a unique blend of science and poetry and have the chance to win some great prizes.  

This year the theme is FOOD, recognising the UN International Year of Family Farming, and National Science Week’s theme ‘Food for our Future’.

With such a broad topic, there’s lots of creative scope. The only rule is: your entry must relate to BOTH science and food.

For more information, visit the RiAus website.
 

     
Try this: Goopy gluten  
 
 
 
Flour, two glasses, bowl, water, measuring spoon
You'll need these things, and a spoon for stirring.
 
Stirring flour into a glass of water
Put two tablespoons of flour and one tablespoon of water into a glass and stir.
 
Pressing the dough
In a bowl, put two tablespoons of flour and one tablespoon of water. Mix them together, then knead the dough by pressing it flat and folding it over.
Folding the dough
This is how to fold the dough over. Keep pressing and folding it for ten minutes.
Washing the dough
Wash the dough in a glass of water, until you are left with a creamy-brown, stretchy blob.
 
Gluten
You have now extracted gluten.
 
 
   
   


You will need

  • Plain flour
  • Water
  • Bowl
  • Two glasses
  • Measuring spoons
  • Spoon
  • Pen and paper

What to do

  1. Fill two glasses with an equal amount of water. Label one as flour and the other as dough.
  2. In the glass labelled flour, put two tablespoons of flour and one tablespoon of water. Stir well. What happens?
  3. Now we are going to make dough. In a bowl, put two tablespoons of flour and one tablespoon of water. Mix together to form a dough.
  4. Using your hands, knead the dough by pressing it flat and folding it over. Keep up this press-fold, press-fold for ten minutes.
  5. Put the kneaded dough in the glass labelled dough. Use your fingers to wash the dough in the water. You’ll see the water become white – this is the starch or carbohydrate in the flour. Keep washing the dough until you are left with just a creamy-brown stretchy blob – it might take five or ten minutes. You have now extracted gluten.
 

What’s happening?

When we wash the dough in water, we are separating the dough into the parts that dissolve in water and those that don’t. Starch is one of the parts that dissolve in water. Gluten does not, so this method allows us to extract it.
 
When you stirred just the flour into the glass labelled flour, you would have noticed that there was no glob of gluten at the end. Why? Gluten is actually formed from two proteins, gliadin and glutenin, both found in flour. When flour is mixed with a bit of water and kneaded, these proteins become hydrated and combine to make gluten. Kneading makes the gluten form a network of fine protein strands. This makes it stick together into a gloopy glob.
 

Applications

Gluten is tough stuff. Play around with your glob of gluten and feel how strong and elastic it is. Gluten gives bread an elastic texture and traps air bubbles, allowing the bread to rise. Too much gluten in a scone, muffin or pancake will make them tough.

In gluten-free cooking, people might use rice and maize flour instead of wheat, as they don’t contain gluten. To get the dough to rise they need to add extra ingredients, such as guar gum, to do the work that gluten would.
 
Washing dough to extract gluten is sometimes used in vegetarian cooking. The gluten is collected and used as a meat-free form of protein also known as seitan. It can be dried and powdered, and then used to make an imitation meat.
 

More information

Extend this activity – try it with different types of flour.
What is gluten?


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Read it!

Parsley plastic? Scientists have found an easier way to turn food scraps into biodegradable plastic.
 

See it!

Artist Sam Van Aken has created a tree that produces 40 different types of stone fruit (PDF). He used a process called grafting, which is commonly used in apple orchards to put a great apple-producing variety onto a variety with good roots.
   
   
 
 
 
Video
Watch it! Extract DNA from a banana at home, with this activity from CSIRO.
 
 
   
    Quiz answers    
   
  1. A barbel is a type of fish.
  2. LOX is liquid oxygen.
  3. a) The Earth’s crust is approximately 40 kilometres thick.
  4. False. Red blood cells are actually smaller than liver cells.
  5. Drag is created by parachutes to slow objects down.
   
  
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