Protein and Starch

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Protein and Starch

Transcript Of Protein and Starch

Protein and Starch

Author: Francisca Jofre Institute for Chemical Education and Nanoscale Science and Engineering Center University of Wisconsin – Madison

Purpose: To learn about foods that contains starch and proteins.

Learning Objectives: 1. To learn about indicators such as iodine. 2. Importance of concentration in a solution. 3. Proteins can be separated from milk by mixing with acid.

Next Generation Science Standards (est. 2013)  PS1.A: Structure and Properties of Matter (partial)  ETS1.A: Defining and Delimiting Engineering Problems

National Science Education Standards (valid 1996-2013):  Standard B: Physical Science o Properties and changes in properties of matter  Standard F: Science in Personal and Social Perspectives o Science and technology in local, national, and global challenges

Grade Level: 3-8

Time: 1 hour

Materials:  Skim milk  Vinegar  Microwavable cups/bowl/dish  Measuring spoon  Graduated cylinder  Baking soda  Cereal  Spaghetti  Peanut butter  Butter

 Pencil  Paper cups  Straws  Wax paper  Masking tape  Tincture of iodine  Dropper  Marshmallow  Yeast (optional)

Safety: This activity involves peanut butter. It can be omitted if any students have peanut allergies or if the building is peanut-free.

Introduction: Have students look at the nutrition labels provided and ask them to identify the main parts of the labels; ask them to find which nutrients are present in all the labels. Show the students that most foods are a mixture of different nutrients such as fat, proteins, carbohydrates, etc. From the labels they can see that carbohydrates play an important role in nutrition and the most popular one around the world is starch. In this activity students will use a simple test to see which sample foods contain starch and the importance of concentration in sample. In this activity they will learn that milk also contains two types of protein, casein and whey, and how to separate them.
Procedures: 1. Starch Search a. Take a paper plate and divide it into as many sections as foods they will test: Crackers, cereal, pasta, peanut butter, butter, milk and marshmallow (yeast is optional). b. Place a small amount of each food on its area of the plate. c. Put a drop of iodine mixture into each different food. d. Take four cups and label them 1, 2, 3, 4. e. Crumble one cracker into each cup. f. Add one tablespoon of water to cup one, two tablespoons to cup 2, three tablespoons to cup 3, and four tablespoons to cup 4. g. Use different straws to mix the water and crackers in each cup until the cracker has completely mixed with the water. h. Take a piece of wax paper and divide it into four sections: 1, 2, 3, 4. i. With the straw from cup one, take a few drops (~3) from the cup and put it on the designated sections of the waxed paper. Repeat the procedure for cups 2 through 4. j. Add ONE drop of iodine solution to the drops of water/cracker mixture.
2. Lumpy Milk a. Have students measure out 30mL of skim milk into a microwavable container. b. Add two tablespoons of vinegar to the skim milk. c. Allow the students to stir the mixture and observe any changes. d. Write down your observations. e. If you have access to a microwave, heat up the mixture for less than a minute. This will cause the clumps to get larger. f. Allow the students to touch the mixture and observe changes. g. Students can repeat steps a-c and then add 1-2 teaspoons of baking soda to create glue.

Discussion: Starch search: Tell students the change in color when adding iodine to foods that contain starch is due to a chemical reaction between the iodine and the starch molecules. Iodine can be used as an indicator for starch products. Ask why the color of iodine was different for each cup containing water and crackers (1,2,3,4), how different concentrations have an effect on the indicator.
Lumpy milk: Explain that the vinegar (increase in acidity) causes the milk proteins (casein) to tangle into solid masses, these are “curds”; the rest of the liquid is “whey” which contains only whey proteins. When milk spoils, it is because chemical processes have made the milk acidic. This acidity causes the proteins to clump and give milk a sour taste. If time permits, allow students to mix some baking soda (about 1/8tsp) and water (about 1tsp) with their casein to make glue. They can also test their glue. Ask the students to use their knowledge of the previous protein activity to predict another way of curdling the milk.
Evaluation: Complete the Protein and Starch Worksheet with the students.
This lesson is the product of the Institute for Chemical Education and the Nanoscale Science and Engineering Center at the University of Wisconsin-Madison.
This Material is based upon work supported by the National Science Foundation under grant number DMR-0425880.
SCIENCountErs Lessons are licensed under a Creative Commons AttributionNonCommercial 4.0 International License. Permissions beyond the scope of this license may
be available by emailing [email protected]