Tortillas are a staple of Mexican food. Their historical roots may go back 5,000 years when corn was first domesticated in the arid Sierra Madre Mountains. Corn dating from that time, and discovered by archaeologists, was much smaller than today’s variety and its history belongs to another lesson. Nevertheless, when Spanish soldiers arrived in Mexico in the 1500’s, they saw Aztecs making the flat breads with corn meal. The Spaniards named the flat bread tortillas or little cakes, after the Spanish word for cake: tort. Hernando Cortez described this food in a letter to the Spanish King. The Spanish soldiers found tortillas useful and tasty; and the recipe spread throughout Europe and beyond. Although the Aztecs were making corn tortillas, wheat tortillas became popular with the introduction of wheat.
This lesson combines tortilla cooking with science: a simple tool, the lever.
First, make tortilla dough.
1. Mix:
2 cups whole wheat flour
1/2 cup all-purpose flour
1 teaspoon baking powder
2. Pulse flour mixture briefly in food processor with
1/4 cup shortening (without transfat)
The fat should be evenly and finely mixed throughout the flour mixture.
3. Put this mixture into a large bowl and make a well in the center. Pour 3/4 cup hot water into the well. Mix with spoon or hands until a dough is formed.
4. Let this dough rest 20 minutes. Then divide into golfball-sized balls.
Shaping the tortillas – and an introduction to the lever.
Hand- patted: In many rural parts of Mexico, women still shape the tortilla dough into flat patties using their hands. Take a ball of dough between your flattened palms and slap back and forth until the dough is flattened. Pay attention to the amount of time and effort you use. Observe the flatness you are able to achieve with this method. Put this hand-patted tortilla on a plate and set aside.
Pressed: Find two heavy hardback books or two clean boards. If using books, either place waxed paper between the books or put the books into large ziplock bags to protect them. Put a ball of dough between the books and press down with your arms to flatten the ball. Pay attention to the effort used in pressing down. Your shoulders, arms, and maybe even your legs are involved. Look at the flattened ball. It should be flatter than your previous hand-patted tortilla.
Pressed with a hand tortilla press: A tortilla press uses leverage to lesson your work. Dust the tortilla press with a little flour. Place a ball inside the press and use your hand to press down on the end of the lever arm. Notice the amount of effort used. You can even press the end of the lever with a finger instead of your entire hand. Observe the flatness of the finished ball. Which method used the least effort and resulted in the flattest tortilla?
How levers work: A lever is a simple machine. It consists of a lever arm and a fulcrum (the point around which the lever swivels). Can you find the lever arm, and the fulcrum on the tortilla press? There are actually two levers at work: the second one is the hinged lid on the press. A lever does some of the work for you. A longer lever does more work than a shorter lever, which is why you want to press on the end of the lever arm when using the tortilla press.
Now cook the tortillas:
Use an electric skillet, electric pancake tray, or a heavy cast iron skillet for best results. Do not use grease on the cooking surface. Wait until the cooking surface is hot and drop the flattened tortilla on it. Cook briefly on each side until the tortilla begins puffing up. Remove with a spatula (another lever!). Serve any way you wish. I like adding a small pat of butter to the hot tortilla, along with cinnamon sugar.
For further discussion: Can you find other levers around your house? The tortilla press is a “pressing lever” and we use many of them on a daily basis. Fingernail clippers, staplers, hammers, and hole punches are examples. Another type of lever might be called a “prying lever.” These would include using a spoon to pry open a lid, a wheelbarrow, the claw end of a hammer.
Science Without a Laboratory 