September 16: The Science of Baking Bread

"So long as you have food in your mouth, you have solved all questions for the time being." – Franz Kafka

Milling flour

Monday, September 16:  
yeast and bread baking
(Sources: The Little Red Hen (Project Gutenberg), Science in School: Bread-baking, teaching science in primary school, Homebaking.org: Second Grade: Science of Baking)

Grade Level: Elementary

Objective:
Students will learn more about fungi, yeast, and chemistry through baking bread.

Materials:
flour, salt, yeast, sugar, olive oil, warm water, baking tray or loaf tin, tea towel, measuring cup, mixing bowl, fork

Class Introduction/hook:
yeast review, flour grinding, and baking soda experiment.

I only had one student in science today--the tiniest class I've ever taught.  My chalet is only a couple hundred meters from school, so with his mother's permission, M and I went on a bread-baking field trip to my kitchen.  We're having a community bread bake today and I wanted M to be able to use his knowledge of yeast and fungi to craft his own contribution to the event.

When M and I got to my kitchen, I asked him what he needed to bake bread, he answered, "Yeast!"

"Is yeast a plant?" I asked

"No." He answered.

"Is yeast an animal?"

"Kind of..."

"What's it related to?"

"Oh!  I remember!  It's a fungi."

I asked M if he remembered the balloon experiment we did last week.  He did.

"Do you remember what the yeast ate?"

"Sugar....!"

M also recalled that yeast needs warm water.  We filled a bowl with a cup and a half of warm water, two tablespoons of sugar, and a teaspoon and a half of quick rise yeast.  We placed the bowl on the table.

M's flour

While we waited for the yeast to begin feeding, M and I talked about quick breads and non-yeast based baking.  We discussed other leavening agents.  To contrast yeast with another baking ingredient we combined 1 teaspoon of baking powder and 1/3 cup of very hot water.  As soon as the powder hit the water the combination brewed and bubbled, foaming and frothing.

"Whoa!"  M shouted.

M and I also explored how flour is made.  We looked at wheat berries and I showed M how to use a mill to process the wheat berries into whole wheat flour.  He churned a couple cups of flour while we waited for our yeast to feed.

When we checked on our yeast, it had also begun to bubble, foam, and smell.  Then we took a slice of already-made bread and looked for the yeast bubbles in that bread.  M understood instantly that the bubbles in the sliced bread were the same kind of bubbles our yeast made, cooked into shape by the flour.

"What does the yeast do for the bread?"  I questioned.

"It makes it rise."

"How?"

"It makes bubbles of air which puff up the flour."  M told me.

M measured out 4 cups of flour and I added three tablespoons of olive oil and two teaspoons of salt.  He mixed the ingredients together until they began to clump then we switched from mixing to kneading.  We talked about kneading technique and discussed it's purpose.  I told M that kneading helps activate the gluten which binds the bread together.  When M had kneaded the bread into a neat ball we headed back to the classroom where we read the Little Red Hen and mapped our bread-baking process on the white board for M's teacher Kim.

"Who will help me bake the bread?"

Washington State content areas covered:

EALR 2: Inquiry 
Big Idea: Inquiry
Core Content: Conducting Investigations

Students know that:
-2-3 INQA Question: Scientific investigations are designed to gain knowledge about the natural world.
-2-3 INQB Investigate: A scientific investigation may include making and following a plan to accurately observe and describe objects, events, and organisms; make and record measurements, and predict outcomes.
-2-3 INQD Investigate: Simple instruments, such as magnifiers, thermometers, and rulers provide more information than scientists can obtain using only their unaided senses.

Students are expected to:
• Explain how observations can lead to new knowledge and new questions about the natural world.
• Work with other students to make and follow a plan to carry out a scientific investigation. Actions may include accurately observing and describing objects, events, and organisms; measuring and recording data; and predicting outcomes.

EALR 4: Physical Science
Big Idea: Properties and Change
Core Content: Properties of Matter

Students know that:
-2-3 PS2A Objects have properties, including size, weight, hardness, color, shape, texture, and magnetism. Unknown substances can sometimes be identified by their properties. List several properties of an object. Select one of several objects that best matches a list of properties. Sort objects by their functions, shapes, and the materials they are composed of. 
-2-3 PS2B An object may be made from different materials. These materials give the object certain properties.

Students are expected to:
-List several properties of an object.
-Select one of several objects that best matches a list of properties.
-Sort objects by their functions, shapes, and the materials they are composed of.
-List properties of common materials. 
-Compare similar objects made of different materials (e.g., a plastic spoon and a metal spoon) and explain how their properties are similar and different.