The Biology of Butter (Emma Lythgoe)

Title: The Biology of Butter

Principle(s) Investigated:

- Use of Fats

- Properties of Phospholipids

- Cell Membranes

Standards:

MS-LS1-2 Develop and use a model to describe the function of a cell as a whole and ways parts of cells contribute to the function.

SL.11-12.5 Make strategic use of digital media (e.g., textual, graphical, audio, visual, and interactive elements) in presentations to enhance understanding of findings, reasoning, and evidence and to add interest. (HS-LS1-2),(HS-LS1-4),(HS-LS1-5),(HS-LS1-7)

LS1.A: Structure and Function

- Within cells, special structures are responsible for particular functions, and the cell membrane forms the boundary that controls what enters and leaves the cell.

Materials:

- Mason jars/ glass containers with lids (craft stores- Michaels, Joanns, etc.)

- Heavy cream or heavy whipping cream (grocery stores)

- Cold water (grocery store)

- Salt (optional) (grocery store)

- Bread (optional) (grocery store)

Procedure:

1. Give each student a mason jar or glass container with a screw-on lid (various sizes will work)

2. Fill the jar halfway to three-quarters of the way full of heavy cream or heavy whipping cream.

3. Once the lid is screwed on tight, have students shake the jar and observe what is happening during the shaking process.

Optional: You may have them take notes at what is happening at different time intervals.

4. Once the jar has a large yellow-ish lump (butter) and a white-ish liquid (buttermilk) have them once again make observations at what the contents of the jar are now.

5. Have each student remove the butter from the jar and place in a large strainer and rinse away excess buttermilk with cold water.

Optional: The students can wash their own butter or the teacher can rinse it to keep everything more hygienic.

6. Bring bread that students could eat some of their butter on (optional)

Student prior knowledge:

- Things are made up of molecules

- Basics of cells- that they have a membrane

- The four macromolecules

Explanation:

When students begin to shake the jar with the cream inside, the substance inside will change (the time varies depending on the jar size, temperature of the liquid, and amount of cream in the jar). The substance will first become whipped cream- dry, stable, and creamy. As the students continue to shake the jar, the substance will then begin the process of becoming butter. Cream is a colloid and contains fat globules and when the fat molecules begin to separate and move, they burst apart and the leaked fat joins together. The students will be able to see yellow globs coming together and with a bit more shaking, the globs can forge together and become one singular glob. The glob will be surrounded by a whiteish substance- buttermilk. From this demonstration, students will be able to see the two properties of a phospholipid, hydrophobic and hydrophilic. Seeing the process in action may help them better conceptualize concepts such as:

Diffusion, Osmosis, Passive transport, Lipid properties, and Cell Membrane Properties.

Questions & Answers:

How does the process of making butter help to explain some of the properties of a phospholipid in a cell?

When making butter, the fat molecules clump together into a glob and the buttermilk (90% water) is pushed away because of the hydrophobic nature of the fat. This can help to illustrate the properties of a phospholipid membrane because the butter and the buttermilk mimic a phospholipid. The butter acts in a similar manor to the lipid tail and the buttermilk acts similarly to the phosphorus head. If more water was to be poured into the jar, the butter would not separate.

Would using chilled cream rather than room temperature cream have an effect on the experiment? If so, what would the effect be?

The room temperature cream would turn into butter at a faster rate because as the fat molecules are being shaken and broken apart, they are clumped together and butter begins to form. The room temperature cream would turn into butter faster because heated molecules move faster and would allow the fat molecules to clump together at a faster rate than if the molecules were cold.

What do you think the molecules in cream mixture looks like when the jar has been shaken for about 5 minutes?

Whipped cream is the precursor to butter. As the cream is shaking, the fat globules are bursting like water balloons and begins to clump together with the other bursted fat molecules. Since whipped cream is lighter and fluffier than butter, the air molecules are involved in the structure. When shaking the jar, the air bubbles are being added into the cream and cause the fat globules to form small chains. The small chains form around air bubbles and attract other fat-stabilized air bubbles which creates the dry and smooth structure that tastes great on pie!

Photograph: https://www.uoguelph.ca/foodscience/book-page/whipped-cream-structure

Applications to Everyday Life:

When baking a cake, one must be sure to properly mix the ingredients together so that the fat added to the cake will not separate from the liquid (usually eggs- 76% water). Properly mixing and making an emulsified cake batter is key. Cakes that are not properly emulsified can be dry, grainy, flat, or even sink in the middle of the pan.

Most sunscreens feel kind of oily when they are applied. After a fresh reapplication, water can even bead off of the surface of your skin. Most sunscreens contain oil or silicone, which are both hydrophobic, to prevent water from washing it away easily. The oil in the sunscreen is attracted to the oil on your skin and helps the sunscreen stick!

Dish soap is both hydrophobic and hydrophilic and resembles a cellular phospholipid. When used for cleaning an oily pan, the soap molecules form around the oil particle, forming a micelle, and allow the oil particle to be carried away by water inside of the structure.