Chemistry of Cooking

Classroom Strategies

This unit will use primarily hands-on laboratory strategies to help students grasp the concepts.  Since students’ lifestyles and cultures vary drastically, I cannot fully rely on every student being able to identify physical and chemical changes in cooking when the truth is their experience in those areas may be limited.  By giving the students the experiences in class, they can draw their own conclusions and extrapolate new ideas.

My classroom and lab are fully integrated.  There are 8 lab stations for student placement.  Seats are assigned for instructional groups consisting of four students.  Due to the number of students seated at each station, it is only natural that they will be talkative.  Therefore, I try to give the students opportunities to engage in conversation every 10-12 minutes whenever my lessons include lectures during direct instruction.  Otherwise, I encourage my students to work in groups all the time.

I will begin the unit with George Washington Carver and the legacy that he left.  As previously stated, this will be the context that will hook students into believing that cooking involves chemistry.  By looking at Carver’s accomplishments as a solution to overcoming oppression, I want students to see that they too have opportunities to overcome oppression using a skillset to create something that the world has never seen before.  This unit is to guide them through the process of what it means to use chemistry to create a product that has a potential market.

To help introduce the unit as well, I will use an inquiry-based activity.  I will use the 5E model where students will follow a series of steps to separate a mixture and record their observations.  Since part of the separation process will require 24 hours to pass, I can have the students begin the laboratory activity at the beginning of class and introduce to them the terminology and concepts as they go through each step of the separation process.

Another strategy I would like to implement is having professionals model their own products.  I want to find people who are in the food services business who could actually verify the use of the chemical separation techniques.  I would like to put together a series of videos where these restaurant owners would prep their ingredients or drinks and use them to engage the students, create virtual homework assignments, and allow the business owners to advertise their product.  I want students to see that the use of chemical separation techniques is essential to providing a quality product and service for humanity.

The last strategy is to give the students a performance-based assessment in which students will engage the design process and publish their work for the public.  The inspiration of this assessment will be based on the television show, Chopped.  After having been taught the chemical separation techniques for processing fruit juices and chocolates, students will be given basket ingredients to draft a recipe and create a fruity beverage or fruit-infused chocolate dessert of their choosing.  Students will use technology to record the processes involved and will publish the series to the web.  I decided to include a social media component because I personally believe that teachers ought to demonstrate how social media ought to be used and give students an opportunity to positively exercise that right.

Inquiry Questions

A common instructional strategy is the questioning technique.  While it is common to pose questions orally in a classroom, the IB program encourages the use of inquiry questions with the intent to provide a roadmap or study guide of the unit.  Ultimately, by providing the students a truncated version of the unit, the inquiry questions give students a sense of what they will ultimately be assessed on.

Factual Questions

• What are the differences between pure substances and mixtures?
• Can mixtures consist of matter in more than one state?
• What are solvents?
• What are emulsifiers?

Conceptual Questions

• How do separation techniques rely on physical properties and chemical properties?
• What is the difference between a state of matter and a phase?
• What is the difference between a polar and nonpolar substance?
• Which conditions result in the most effective separation process?

Debatable Questions

• Can all mixtures be separated?
• How have our personal food preferences developed along with our understanding of materials?
• Does our understanding the nature of mixtures improve our ability to express creativity in cooking?
• Is protest the best way to prove that our lives matter?
• If Carver used science to overcome financial oppression, then could we apply this today in the BLM movement?

Activity 1: Confectionery Chemistry, Round 1 – Microwave-Assisted Extraction of Fat from Chocolate

For the Teacher:  Before beginning this activity, students should already be able to state the three states of matter and differentiate between physical and chemical properties of substances.  I would use this as an inquiry lesson on homogeneous and heterogeneous mixtures.  Students would begin class with this activity.  As they reach different stages of the activity, there are moments that lend themselves to dialogue with the students and this time can be used to elaborate on the process of separating fat from chocolate.  When elaborating, this is the opportunity to introduce vocabulary such as phases, immiscibility, emulsifier, etc.

For the Student:  Welcome to the first round of Confectionery Chemistry!  The goal of round 1 is to use the microwave oven as a tool for removing fat from chocolate and to determine how much fat is in the sample of chocolate provided.  Participants are expected to follow the procedures to isolate chocolate and then calculate how much was removed.  The team that is closest to the true value of fat content will win the first round.

Materials

Dark, milk, and white chocolate, olive oil, 91% or higher isopropanol, microwave safe mini-containers (~100 mL), graduated cylinders or measuring spoons, balance, plastic knives or scalpels, microwave oven (adjustable power output of 250 W and below).

Procedures for Microwave-Assisted Extraction

Preparing chocolate for microwave-assisted extraction

1. Obtain a piece of chocolate (dark, milk, or white) and record your observations of the chocolate in the table following the procedures (OBS 1).
2. Tare/zero a balance.  Measure ~5 g of chocolate on the balance.  Record your exact measurement. 
3. Transfer the 5-gram sample of chocolate into a small microwaveable container (~100 mL in size).
4. Add 1 mL of water to the container containing chocolate.
5. Add 30 mL of olive oil to the container.

Preheating chocolate for fat extraction

1. Adjust the power of the microwave oven to 250 W or less.  For a 700 W microwave oven, the microwave oven must be set to 30% power, which is the equivalent of 210 W.  You must follow your microwave oven’s specific instructions to adjust the power output.
2. Place the container containing chocolate, water, and olive oil into the microwave oven and run the microwave oven for 60 seconds.
3. Allow the mixture to rest for 120 seconds before handling.
4. Gently swirl the mixture for 30 seconds and record your observations (OBS 2).
5. Add 10 mL of isopropyl alcohol.
6. Vigorously agitate the mixture for 30 seconds.

MAE and fat determination from chocolate

1. Adjust the power of the microwave oven to its lowest setting.  The recommended power output is 25 W or 10% power.  (This experiment was tested to work with a 70 W power output).
2. Place the mixture back into the microwave oven for 360 seconds (6 minutes).
3. When the microwave oven is finished, allow the mixture to rest for 120 seconds (2 minutes) before handling.
4. Remove the mixture from the microwave oven and record your observations (OBS 3).

Separation of chocolate layer from mixture

1. Place the lid onto the container and transfer the contents into a freezer overnight.
2. On the following day, remove the containers from the freezer.  Remove the lid and record your observations (OBS 4).
3. Remove frozen solid from the container.  Using a butter knife (spatula-like tool) separate the chocolate from the olive oil layer.
4. Measure the mass of the chocolate removed using a balance.
5. Calculate the mass of fat removed and its percentage.  Compare calculation to contents of food label.

Data Table

Construct a data table that collects the following information:  Initial mass of chocolate squares, Final mass of chocolate, Calculated mass of fat extracted, and Percent of fat extracted.

Observations (OBS)

Analysis Questions

• On a scale of one to 5, how would you rate the procedure to remove fat from chocolate in terms of ease.
• If you were trying to reduce the fat in chocolate, would you recommend this procedure? Explain your reasoning.
• Predict what would happen to the taste of the chocolate if the fat is reduced.