Education Standards
Flour Protein Content
Overview
What role does protein content have in the selection of the flour used in different baked products? In this lesson, students will determine the protein content in various flours by performing a stretch test and interpreting their data.
Overview
Essential Question
How does the protein content of flour influence the sensory characteristics of bread?
Learning Objectives
Identify commonly used flours in the food industry.
Examine the role of protein in providing structure.
Justify the use of specific flours in baked products.
Equipment and Materials
Per Class
- Suggested Flour Samples
- All-Purpose Flour
- Whole-Wheat Flour
- Corn Flour
- Soy Flour
- Electronic Balance
- Distilled Water
Per Student
- Safety Glasses
- Hairnet
- Pencil
Per Student Pair
- Cup (9 oz)
- Graduated Cup (30 mL)
- Metric Ruler
Lesson Plan
Background Information
Twenty-one different grain types make up the bulk of the human diet wordwide. These grains contain essential nutrients needed to nourish your body such as carbohydrates, fats and oils, vitamins and minerals, and protein. Protein in flour gives food strength and structure; you can observe the protein content in flour by stretching bread dough - stronger doughs will have more protein. Bakers select flour based on which protein content is best for what they are baking.
Interest Approach
Facilitate a discussion with students about if any of them or their parents enjoy baking at home; ask them what they enjoy baking. Transition into asking them about the recipes they use while baking and some of the ingredients in the recipe. Explain that flour is an important ingredient in many baked products because the protein (gluten) in it provides structure to the dough.
Students may make a connection that some people are gluten intolerant - use this to introduce the concept that some grains processed to make flour are naturally gluten-free. The different protein contents in those flours will influence the types of products they are used in while baking.
Career Connections
- Dietician
- Food Meal Supervisor
- Food Processer
Experimental Procedure
- Place a 9oz cup on an electronic balance and press Zero or Tare.
- Obtain a labeled flour sample from your teacher.
- Mix a bread dough.
- Use a 30mL graduated cup to add 50g of the flour sample into the cup on the balance.
- Pour the flour into a quart-sized bag.
- Measure 30mL of warm distilled water in the graduated cup.
- Mix the flour and water in a quart-sized bag.
- Knead the dough in the bag for one minute, as demonstrated by your teacher.
- Do not overwork the dough ball.
- Test the strength of the dough ball.
- Remove the dough from the bag and form it into a ball.
- Pinch the dough with your thumb and pointer finger.
- Your thumbs should not be touching.
- Line your thumb up with zero on the ruler.
- Slowly and gently stretch the dough while your right thumb stays at zero.
- Stop moving your hands as soon as the dough breaks.
- Have your partner measure the distance in centimeters between your right and left thumb with a ruler when the dough breaks.
- Record the length in Table 1.
- Knead the dough five times with your hands and reform the dough into a ball.
- Repeat the strength test in Step 5 with the same dough, and record it in Table 1.
- Repeat Steps 2-7 with each flour sample provided by your teacher.
- Dispose of the dough ball once each measurement has been collected.
- Calculate each flour's average length by using the equation below.
Average Length = (Test 1 Length + Test 2 Length) / 2
Conclusion/Check for Understanding
After the conclusion of student data collection and cleaning up of materials, bring the class back together and have students discuss their results in small groups. Discussion should be focused on which flour samples had the highest average length when the dough ball was stretched. Have students share their results with the whole class and identify if there were any varying results.
- Which dough was the most elastic? Which dough was the least elestic?
- Cakes require flour with a lower protein content. Which flour is best suited for cakes?
- When might a baker use an alternative flour that does not contain gluten?
Extension Activity
Students should research grains that are commonly used to produce flours and identify which grains do and do not contain gluten. Study the anatomy of the seed and identify structural differences between grains that may reveal where protein is stored.