Stretch your mind to understand elasticity

By Carlin Hsueh

Download the full elasticity poster.

My name is Carlin (pronounced Car-leen) and I’m a scientist. But that’s not the only thing I’m interested in. Along with doing cutting-edge research in nanotechnology and biotechnology at UCLA, I also enjoy volunteering at outreach programs connect science with our everyday lives. I love to eat, and when I’m not locked up in the lab all night I also enjoy to cook. Working on Top Chef Masters was a dream come true, and it was great to have a partner like Naomi Pomeroy. Naomi is the chef and owner of Beast, an intimate French restaurant in Portland, Oregon. She likes to describe her food as refined grandmother’s food. Luckily for me, Naomi actually liked learning about science when she was in school, so explaining our topic, elasticity, and building a dish around it was really fun.

A rubber band is elastic. You can stretch it and once you let go (carefully, safety first) it will return to its original shape.

At first you might not think elasticity and food go together. However, elasticity is very present in the food we cook and it can be something fun to play around with when making dishes with interesting textures. Elasticity, the springiness or stretchiness of a material, is how much an object returns to its original shape after being deformed.  A rubber band or metal spring (like a slinky) is a great example of elasticity. Stretch a rubber band as much as you can and it will keep bouncing back to its original shape.

However, if you stretch the rubber band or metal spring too far you end up permanently deforming the material (meaning it gets bent out of shape). When you permanently deform something without breaking it we call that plasticity. An easy way of remembering plasticity is thinking about a plastic bag. When you pull the bag really hard you can stretch the plastic bag and see stretch marks in the bag as you keep pulling. When you let go of the bag, it doesn’t spring back and there’s not much you can do to make it go back to its original shape. The plastic bag is experiencing plasticity.

Jello is elastic. Photo Credit: http://sarahbarchyn.files.wordpress.com/2009/10/jello3.jpg?w=420

You can think of elasticity in chewy and stretchy foods. And just like in science, you can play around with elasticity to create new and exciting textures and flavors. Want more wiggle in your jiggle when making Jello? Just alter the ratio of water to gelatin and you can get very elastic Jello that can bounce off the walls or very jiggly Jello that wiggles for minutes and melts in your mouth?

As a way to get the chefs’ culinary juices flowing, I used pizza dough in my demonstration of elasticity. Yup — Pizza dough is quite elastic! Have you ever tried to roll out pizza dough? It really likes to spring back each time you try to stretch it out. This elasticity in the dough results from molecules called gluten. Gluten is like an elastic spring, and so the more gluten you have in your dough the more elastic it becomes (imagine having a single rubber band and then intertwining more and more of them until you get a super bungee cord). The elasticity of the pizza dough will determine what kind of crust you get after baking. Elastic dough made with bread flour will give you a chewy fluffy crust while low elastic dough made with cake flour will give you thin and brittle crust.

In the image you can see that dough is made up of tangled glutenin and gliadin molecules, which make up gluten. As the dough is stretched this gluten structure also gets stretched and the molecules become straighter. Unfortunately, these molecules prefer to be balled up so they resist this stretching. When you let go of the dough it springs back as the molecules return to their balled-up, tangled state. However, if you overstretch the dough you permanently damage the gluten structure and the dough tears or stays stretched out. Photo Credit: Ioana Urma

Using lab equipment to cook food, they don’t teach that in school.

Chef Naomi liked the idea of using pizza dough in her main dish. We decided to make two kinds of pizzas, one with high gluten flour and one with low gluten flour. However, because the chefs had to cook with lab equipment only (it wouldn’t be Top Chef without a twist) she decided to deep fry the pizza dough instead of baking it.

We decided to add a smorgasbord of elasticity components to the dish. The two pizzas would contrast each other, one would have melted stretchy cheese and the other would have uncooked tougher cheese; one would have springy mushrooms and the other would have a veal stock gelee (a savory gelatin).

Not the same dish we made in the episode but pizza nonetheless. So much work was spent stretching that dough!

Additionally, we separated each elastic ingredient into petri dishes so that students could poke and prod the items. Just eating the pizzas helped students see the elasticity. Students who ate the melted cheese pizza had long cheese strings dangling from their mouths and those who ate the pizza with the veal stock gelee felt the savory gelatin melt in their mouth without stretching (heat causes the collagen in gelatin to break apart and melt).

Finished product, with warm oozing cheese (plasticity)

The pizzas seemed like a big hit with the students and the judges. The audience really liked being able to stretch and poke the different kinds of bread dough to feel the difference in elasticity. They also liked poking the cheese and mushrooms to see them spring back into shape and shaking the gelatin to watch it jiggle.

The scientists in front of the Top Chef Masters kitchen. What an amazing experience!

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4 Responses to Stretch your mind to understand elasticity

  1. Adi June 20, 2011 at 12:51 pm #

    Thanks for touchign on this interesting food science topic!
    Gluten is composed of gliadin and glutenin. Though glutenin is elastic, gliadin is more cohesive. Therefore, if your dough is high in glutenin, the insoluble glutalin protein fraction, it will be highly elastic.

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