Students will learn the physical components and nutritional composition of a grain, understand the function of the protein gluten in the structure of bread products, and investigate how mechanical and chemical digestion begins with salivary amylase in the mouth. Grades 6-8

amylose: a component of starch consisting of long, straight chains of glucose units

bran: the multi-layered, hard outer covering of a kernel of cereal grain

chemical digestion: the breakdown of food molecules by digestive enzymes and chemicals

complex carbohydrate: polysaccharides that contain hundreds or thousands of monosaccharide units; found in foods such as starch and fiber and have to be broken down completely for absorption

endosperm: tissue formed within a seed that contains energy (starch) and protein for the germinating seed

flour: a powdery substance obtained by grinding grain (usually wheat), which is used to make bread and many other products

germ: the embryo of a cereal grain seed

gluten: a tough, elastic protein substance in flour, especially from wheat, that holds dough together and makes it sticky

mechanical digestion: the physical act of breaking up food particles through chewing and contractions of the stomach and intestines

salivary amylase: the enzyme found in human saliva that aids in the breakdown of starch in the mouth

simple carbohydrate: carbohydrate products that contain only one or two sugar molecules; these are the quickest sources of energy because they are easily absorbed

whole grain: contains all three edible parts (the endosperm, bran, and germ) in the same proportions as the harvested grain seed before it is processed

FoodMASTER (Food, Math and Science Teaching Enhancement Resource) is a compilation of programs aimed at using food as a tool to teach mathematics and science. For more information see the Background & Introduction to FoodMASTER. This lesson is one in a series of lessons designed for middle school. 

Whole grains have three parts called the bran, endosperm, and germ. The bran is the outer layer of the kernel. It contains antioxidants, B vitamins, and fiber. The germ is the embryo, which can be used to sprout a new plant. It contains B vitamins, some protein, minerals, and healthy fats. The endosperm is the food supply for the germ. It is the largest portion of the kernel and contains carbohydrates (starches), protein, and some vitamins and minerals. If grains are not whole, they have been refined. This process strips the kernel of the bran and germ to extend shelf life. This process removes many of the nutritional benefits, including the antioxidants. 

Iodine can be used to detect starch. The iodine molecule moves inside the starch chain, producing a deep blue color. More specifically, when an iodine solution is diluted with water, the iodine atoms are arranged in a random order within the liquid. This random distribution produces a light yellow color. When the iodine solution comes into contact with starch (long chain carbohydrates), the iodine atoms organize into a non-random arrangement, and turn blue. This blue color indicates that starch is present. However, when starch is broken down further into simple carbohydrates (no longer starch), the iodine molecules arrange in a random order again, producing the light yellow color. 

Gluten is a protein found in wheat, barley, and rye that provides structure in baked products. Gluten is a linkage between the proteins glutenin and gliadin. Gluten develops through the formation of these bonds by the addition of water and manipulation (e.g. kneading). In general, flours with higher gluten content are high protein flours, and those with lower gluten content are low protein flours. High protein flours are used to make foods like bread and pasta, while weak/low protein flours are used to make foods like cake and pastries. Besides the type of flour, gluten strength can be controlled by manipulating the dough manually or by adding other substances to the dough. For example:

• Kneading the dough strengthens and organizes the gluten mesh. Folding, pressing, and stretching dough until it has reached the desired form is called kneading
• Adding salt also greatly strengthens the gluten mesh
• Adding sugar limits the development of gluten
• Adding acids weakens the gluten mesh
• Adding fats weakens the gluten

Each of the treatments above can be used to make different foods. For example, you knead and manipulate the dough much longer when making pizza crust as opposed to the time you would take to make a cake batter. The more you knead or stir the mixture, the more the gluten develops. This leads to stronger bonds and structure.

The protein gluten may be harmful to some. Individuals who have Celiac disease are allergic to gluten. When consumed, the gluten will cause an auto-immune response in the small intestine, leading to inflammation. The inflammation causes damage to the lining of the small intestine. The provided graphic below provides a visual of the damage caused to the intestinal epithelial cells of someone with Celiac disease. This will prevent absorption of some nutrients. If left untreated, it can cause developmental problems in children due to the nutrient deprivation. Individuals with Celiac disease must consume a gluten-free diet to avoid gastric distress and malabsorption. Celiac disease is not the only cause of gluten-related reactions. Individuals can also have non-celiac gluten sensitivity (NCGS). NCGS can cause similar symptoms as Celiac disease; however, an auto-immune response is not triggered and intestinal damage is not caused. Recent research has identified Fermentable Oligosaccharides, Disaccharides, Monosaccharides And Polyols (FODMAPs), a group of poorly digested carbohydrates, as a possible cause of the NCGS-type symptoms such as bloating, diarrhea or constipation. 

Amylose and amylopectin are the common starch molecules found in food. Amylopectin forms a long, branched chain, while amylose forms a long, straight chain, making it easier to digest. Amylase is the enzyme our bodies use to break down amylose. The diagram at the beginning of the student lab investigation displays this relationship pictorially. Amylose undergoes hydrolysis (addition of a water molecule) in the presence of the enzyme amylase. This reaction causes the amylose chain, a complex carbohydrate (polysaccharide), to breakdown into smaller units known as simple carbohydrates (disaccharides followed by monosaccharides). As mentioned above, starch is a polysaccharide. All starches are considered carbohydrates, but not all carbohydrates are starches. Iodine will detect starch molecules. Therefore, a positive test will result when the iodine solution comes into contact with bread or other starchy foods (e.g. potatoes). However, once amylase has had time to break down the starch molecules, the iodine solution will no longer detect starch. This is because, amylose is broken down by amylase into simple carbohydrate molecules that are no longer complex, like starch molecules.

1. Ask students to define a "whole grain." Ask students to use their prior knowledge to identify specific food sources of whole grains and the health benefits of consuming whole grains.
2. Give each student one copy of the Gratifying Grains student handout. Students will need a Nutrition Facts label from whole grain bread and white bread for comparison. If you choose to use the provided grain food labels, see the Gratifying Grains Teacher Key for answers to the Investigating Your Health lab questions. Answers to questions based on other food labels will vary.
3. If completed in-class, allow students to work in small groups on the worksheet to further explore the topic and respond to questions.
4. Follow-up with a class discussion about student findings related to the health benefits of whole grains and student generated ideas for increasing whole grain consumption. 

Lab 1: Great Grains

Teacher Preparation:

• Review information found in the Background Agricultural Connections section of the lesson, lesson Procedures, and the attached Essential Files.
• Place corn kernels in a plastic container filled with water the night before implementing the lab.
• Paper plates may be pre-labeled for student dissection. Divide the paper plate into thirds and label each section “Bran”, “Germ”, or “Endosperm”.

Procedures:

1. Distribute lab materials. It is recommended that materials are organized into stations for easier distribution. Students should be arranged in small groups of 4-5. Each group should receive the lab supplies outlined in the Materials section as well as 1 copy of the Great Grains lab sheet and the Flour Power handout.
2. Ask students to read Flour Power and complete the focus questions for this lab investigation.
3. Before beginning the lab investigation:
   • Require students to wash their hands.
   • Emphasize the importance of practicing good food safety behaviors by not consuming substances used as part of the lab investigation.
   • Launch the student lab investigation by asking students to make a prediction about which portion of the grain contains the starch.
4. Show students the provided video lab demonstration, Lab I: Great Grains. The video will help students understand how to dissect their corn kernel and identify the physical components. 
   • It is recommended that the teacher slice the kernel if student ability and/or maturity are a concern. 
5. After completing the lab, students should find the endosperm contains the starch within a grain. The endosperm will react with the iodine resulting in a dark brown color, while the bran and germ will produce a colorless or slight color change reaction (negative test).
6. Allow students to work in small groups to complete the Great Grains lab sheet to further explore the topic and respond to lab questions. Encourage students to refer to the table in the reading to help support their conclusions. Follow-up with a class discussion about whole grains and their health benefits.

Lab 2: Globs of Gluten

Teacher Preparation:

• Review information found in the Background Agricultural Connections section of the lesson, lesson Procedures, and the attached Essential Files.
• Assign each student group 1 flour type (all-purpose, cake, or bread).
• For each group, measure 1 cup of the assigned flour into a small plastic bag and label.
• For easier clean up, cover each lab table with a plastic tablecloth. You may choose to tape the ends of the tablecloth to the underside of the table to ensure it is secure. Alternatives to plastic cloths are plastic wrap, wax paper, medium-size cutting boards, or a cut-up brown paper grocery bag.
• Prior to or at the beginning of the lesson you will need to obtain very warm water for students to wash their flour balls. If you do not have access to warm water from a faucet, you will need to heat water using a hot plate, large pot, or microwave.
• Students are instructed to wash their flour balls in bowls filled with warm water in this lab. If sink access is not a concern for your classroom, this step can be done in a sink with warm running water. Flour balls may be placed in a strainer and warm water run over it.
  • Important Note: It is vital students use warm water to wash their flour balls. Cold water will cause the gluten to tighten, making it more difficult to wash the starch away from the protein.

Procedures:

1. Distribute lab materials. It is recommended that materials are organized into stations for easier distribution. Students should be arranged in small groups of 4-5. Each group should receive the lab supplies outlined in the Materials section as well as 1 copy of the Globs of Gluten lab sheet.
2. Before beginning the lab investigation:
   • Require students to wash their hands.
   • Emphasize the importance of practicing good food safety behaviors by not consuming substances used as part of the lab investigation.
   • Launch the student lab investigation by asking students to make a prediction about which flour contains the most gluten (protein).
3. Show students the provided video lab demonstration, Lab II: Globs of Gluten. The video will help students understand how to knead and show them an example of a gluten ball. As students complete the lab note the following:
   • TIP: Students may not understand how to “knead” dough. Demonstrate kneading of the dough or or point it out in the lab video.
   • Students working with cake flour should only add 1/8 cup of water to their flour mixture. If more water is added, the group may need additional flour to form non-sticky dough.
   • If students find their dough is sticking to their fingers or their kneading surface, additional flour is needed.
   • While students allow their flour balls to rest, they should be directed to clear their spaces and obtain warm water. The warm water is needed to rinse away the starch molecules from the flour ball. As the students wash their flour balls, the water will take on a milky appearance. The dough will turn a yellow-brown color and begin to feel like wet clay. If the students see small white nodules, this indicates there is starch that still needs to be washed away.
   • The final gluten ball should ooze a clear liquid when taken out of the water and squeezed. The final gluten ball should look stringy and be tough (resistant to any other shape). Gluten balls should be kept in a plastic bag and stored in the refrigerator. After approximately 24 hours, gluten balls are shapeable and pliable. 
4. After completing the lab, students should find bread flour contains the largest amount of protein followed by all-purpose flour and cake flour. The flour type with the most protein should produce the largest gluten ball. The larger amount of protein present will result in greater formation of gluten in the dough. The amount of kneading will directly impact the formation of gluten. If students failed to knead their flour ball for the specified amount of time, it may impact the observed results.
5. Allow students to work in small groups on the Globs of Gluten lab sheet to further explore the topic and respond to lab questions.
6. Follow-up with a class discussion about gluten in the diet.

Lab 3: Amylase in Action

Teacher Preparation:

• Review information found in the Background Agricultural Connections section of the lesson, lesson Procedures, and the attached Essential Files.
• Mix 5 mL iodine with 35 mL water to make approximately 40 mL. The diluted iodine solution should have a dark tan color. The lab investigation will not work without this step. Iodine solution that has not been diluted will result in positive starch tests regardless of exposure to amylase. Divide the iodine solution into 6 small cups (1 per group). Groups should have at least 1 mL solution per starch test (6mL total).
• Label 6 paper plates (1 per group). Divide the plate in half by bread type (wheat and white). Divide each side of the plate into thirds to represent control, 30 seconds, and 1:30 minutes for each bread type.
• You may wish to provide students who volunteer to chew bread samples with water during the investigation.

Procedures:

1. Consider having your students research the beginning stages of digestion (mechanical and chemical) prior to beginning the lab investigation.
2. Distribute lab materials. It is recommended that materials are organized into stations for easier distribution. Students should be arranged in small groups of 4-5. Each group should receive the lab supplies outlined in the Materials section as well as 1 copy of the Amylase in Action lab sheet.
3. Before beginning the lab investigation:
   • Require students to wash their hands.
   • Allow students to taste a sample of the bread in the lesson prior to beginning any investigation procedures. This process is important for increasing student exposure to healthy foods and decreasing the likelihood that students will be tempted to taste foods included as investigation materials.
   • Emphasize the importance of practicing good food safety behaviors by not consuming substances used as part of the lab investigation.
4. Begin the student lab investigation by asking students to make a prediction about which bread will test positive for starch after being exposed to amylase.
5. Show students the provided video lab demonstration, Lab III: Amylase in Action. The video will help students understand how to read a negative and positive test for starch using the iodine solution. 
   1. Control: The un-chewed bread will produce a positive test for starch. The iodine should turn the bread a dark brown or black color at the point of contact. See Teacher Background for more information related to the iodine starch test.
   2. White Bread: At 30 seconds students should still have a positive test for starch, however, the color of the iodine on the chewed bread sample will not be as dark compared to the un-chewed bread. If this sample is allowed to sit longer, the test may produce a negative outcome because the small amount of amylase present will continue to break down the starch present in the bread (see Teacher Bites). The 1:30 minutes chewed bread sample should produce a negative test for starch. This bread sample has had greater exposure to the amylase enzyme, allowing for greater break down of starch molecules into smaller units (simple carbohydrates).
   3. Wheat Bread: Observations of the wheat bread should be identical to the white bread samples. The presence of fiber and vitamins/minerals does not interfere with amylase’s ability to break down the starch molecules to smaller units.
6. Allow students to work in small groups on the Amylase in Action lab sheet to further explore the topic and respond to lab questions.
7. Follow-up with a class discussion about mechanical versus chemical digestion and the importance of each. 

After conducting these activities, review and summarize the following key concepts:

• Foods containing whole grains are made using the complete grain kernel. Refined grains typically only use the endosperm.
• Grains include wheat, rice, oats, cornmeal, or barley.
• Wheat is processed into flour for breads, cakes, and other foods.

1. Carbohydrates and Sugar, Nemours KidsHealth/
2. Celiac Disease: Fast Facts, Beyond Celiac

This lesson was partnered with East Carolina University. The FoodMASTER program was supported by the Science Education Partnership Award (SEPA) which is funded from the National Center for Research Resources, a component of the National Institutes of Health.

• Primary Authors:
  • Virginia Stage, PhD, RDN, LDN
  • Mary White
  • Ashley Roseno, MAEd, MS, RDN, LDN
  • Melani W. Duffrin, PhD, RDN, LDN
• Graphic Design: Cara Cairns Design, LLC

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