7
Gluten
Exercises and Experiments
Exercise 1: Increasing Gluten Development in Batters and Doughs
In the spaces that follow, list all the ways you know that will increase gluten development in batters and doughs. For the purposes of this exercise, focus entirely on gluten structure, not on structure in general. Don’t be concerned about other changes that might make your product less desirable in other ways. Be specific and be practical; that is, think of changes you could tell an assistant to execute. Be sure to start each line with an action word such as the following: add, increase, decrease, change, omit, include, use. While each item might not apply to all types of products, each should work in at least one. Follow the format used in the first two, which are done for you, and see if you can add at least ten more ways.
1 Use bread flour instead of pastry flour.
2 Increase the amount of water in dough where gluten is not fully hydrated.
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Exercise 2: Functions of Ingredients in Bread
On a sheet of paper, copy the name of each ingredient listed on the label of any brand of bread from the supermarket. State what the ingredient is (flour, variety grain, sweetener, fat or oil, emulsifier, maturing agent, etc.), then briefly explain its function in the bread. Use your entire textbook, not just this chapter, as a reference. For the flour, state whether it is bleached or unbleached; if it is bleached, state which bleaching agent you believe was likely used. Also state whether the flour is enriched, why it is enriched, and which vitamins and minerals were added for enrichment. Attach the original label to the assignment.
Experiment 3: Amount and Quality of Gluten in Different Flours
Objectives
Gain an increased understanding of different flours and the gluten they contain by
• Kneading doughs by hand
• Separating out the gluten contained in each flour
• Measuring the size of the gluten ball from each flour
• Evaluating the qualities of gluten from each flour
Products Prepared
Gluten balls made from
• Vital wheat gluten
• High-gluten flour
• Bread flour
• Pastry flour
• Cake flour
• Whole wheat flour
• White rye flour
• Corn flour
• Other, if desired (all-purpose flour, artisan bread flour, white whole wheat flour, whole wheat pastry flour, durum flour, etc.)
Materials and Equipment
• Scale
• Stainless-steel bowls, 4-quart (4-liter) or larger, one per gluten ball
• Sieves or strainers, one per gluten ball
Procedure
1 Prepare dough from each flour by combining 8 ounces (250 grams) flour with 4 ounces (125 grams) water. Set aside a small amount of the 8 ounces (250 grams) of flour to use to dust the table surface.
2 Add more water to each flour, as necessary, until dough is able to be kneaded. You do not need to keep track of the amount of water added to the dough.
3 Knead each dough by hand for 5–7 minutes, or until gluten is fully developed. Use flour set aside to prevent dough from sticking; do not add any additional flour unless necessary. If additional flour is necessary, weigh the amount of flour. Record the total weight of flour (8 ounces/250 grams plus any additional flour) in Results Table 1, which follows.
4 Place dough in bowls and fill bowls with cool water. Time permitting, let gluten balls soak in water for 20 minutes.
5 Knead and tear apart each dough by hand while it is submerged (Figure 7.9), until the water is very cloudy (cloudiness is primarily from the starch, bran particles, and gums coming from the flour). For flours that have little or no cohesive gluten (rye flour, cake flour, corn flour), the dough will fall apart easily when placed in water; for these flours, swish the bits of dough through water to remove starch.
Figure 7.9 In back, rinsing and kneading a gluten ball. In front, gluten balls made from bread, pastry, and cake flours.
6 Gather bits of dough into a ball or allow particles to settle to the bottom of the bowl and drain off cloudy water, replacing it with fresh cool water. For cake flour, use a fine sieve (chinois) to prevent loss of dough and bits of gluten. If desired, also use sieve or strainer to retrieve bran particles from whole wheat flour. Set aside bran particles and display with whole wheat gluten ball.
7 Continue this process until water squeezed from gluten ball is clear; this will take 20 minutes or more of continuous kneading and tearing for most doughs, longer with cake flour.
8 When water is completely clear, drain off and squeeze the gluten ball to remove as much excess water as possible. For rye and corn flour, no gluten ball will form. Instead, save a small amount of partially washed dough. Be sure that these are clearly labeled as bits of partially washed dough and not as gluten balls.
9 Pat gluten balls dry.
10 Find information on the typical percent protein content for each flour from this textbook and record information in Results Table 1.
11 Allow the gluten balls to relax for a minimum of fifteen minutes before evaluating. This allows time for gluten network to recover from the washing process.
Results
1 Weigh each gluten ball on scale and record results in Results Table 1. Use the two blank rows to record results for any other types of flours tested. Do not weigh partially washed dough from rye and corn flours; these are not gluten balls. Gluten balls do not form from these flours.
2 Estimate the percent of gluten in flour as follows, and record results in Results Table 1:
100 × Weight of Gluten BallPercent Gluten in Flour = / ------
3 × Weight of Flour
This calculation is based on the assumption that gluten absorbs two times its weight in water, meaning that every ounce (30 grams) of the gluten ball is 1⁄3 ounce (10 grams) gluten. This calculation also assumes that the gluten ball is only gluten. In fact, lipids, ash, and some starch and gums are trapped in gluten balls.
Where the total amount of flour is 8 ounces, the formula can be simplified to 4.2 × weight of gluten ball. For 250 grams flour, the simplified formula is 0.13 × weight of gluten ball.
Results Table 1 Amount of Gluten in Flours
Type of Flour / Weight of Flour (ounces or grams) / Weight of Gluten Ball (ounces or grams) / Estimated Percent Gluten in Flour (from calculation) / Typical Percent Protein in Flour (from text) / Additional CommentsVital wheat gluten
High-gluten
Bread
Pastry
Cake
Whole wheat
White rye
Corn flour
3 Evaluate each relaxed gluten ball for the quality of its gluten and record results in Results Table 2. To do this, gently pull each ball between your hands, much as you pull bread dough to form a windowpane. Rotate the ball as you do this, so that you are pulling it in all directions. Next, gently poke the stretched dough with your fingertips, to test its ability to withstand tearing. Be sure to compare each in turn with the gluten ball made from bread flour and evaluate for strength and cohesiveness, using the following guidelines.
• Strength (tenacity): The harder it is to stretch, the stronger the gluten. If the gluten ball falls apart and is not cohesive enough to stretch, record that it does not stretch.
• Cohesiveness (ability to resist tearing): The better it forms a thin film that resists tearing when poked, the more cohesive it is.
• If desired, also evaluate for extensibility (how far dough stretches) and elasticity/springiness (how well the gluten ball springs back when pressed or stretched) and record in Additional Comments column.
4 Evaluate the partially washed rye and corn doughs. While these are not gluten balls, they do have properties that are important to note. Evaluate the doughs for strength and cohesiveness; that is, do they hold together when pressed, if not stretched? Also record an appropriate description of the consistency of each in the Additional Comments column. For example, record if washed dough feels slick and slimy, if it is more like wet sand and crumbles, if it is pasty, etc.
Results Table 2 Quality of Gluten from Different Flours
Vital wheat gluten
High-gluten
Bread
Pastry
Cake
Whole wheat
White rye
Corn
Sources of Error
List any sources of error that might make it difficult to draw the proper conclusions from your experiment. In particular, consider whether kneading was complete; whether gluten balls were thoroughly rinsed and water squeezed from final gluten ball ran clear; whether bits of gluten were lost during the rinse; whether bran was completely separated from whole wheat dough.
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State what you could do differently next time to minimize or eliminate each source of error.
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Conclusions
Select one from the choices in bold or fill in the blanks.
1 The gluten ball made from pastry flour was smaller larger than the gluten ball made from bread flour. This is because pastry flour is from a soft hard wheat that is lower higher in protein than bread flour. The difference in size was small moderate large.
2 When stretched, the gluten ball made from pastry flour tore more easily than less easily than the same amount as the gluten ball made from bread flour. This is because the gluten that forms from pastry flour is stronger than weaker than the same as gluten that forms from bread flour. The difference in strength between the gluten balls was small moderate large.
3 The gluten ball made from cake flour was larger smaller than the gluten ball made from pastry flour. This is partly because cake flour is generally slightly higher lower in protein than pastry flour. It is also because cake flour has been treated with potassium bromate benzoyl peroxide chlorine, a bleaching agent that weakens strengthens gluten. The difference in size between the gluten balls was small moderate large.
4 When stretched, the gluten ball made from cake flour fell apart held together well. This is largely because the bleaching agent potassium bromate benzoyl peroxide chlorine has been added to cake flour.
5 The gluten ball made from whole wheat flour was larger than smaller than the same size as the gluten ball made from bread flour. It also formed gluten that was stronger than weaker than the same as the gluten that formed from bread flour. This is primarily because
6 The flour that formed the largest gluten ball was This flour formed the largest gluten ball because
7 While neither rye nor corn form gluten, rye corn flour formed dough that had some strength and cohesiveness; that is, that held together somewhat. The dough held together because the flour is high in soluble pentosan gums starch, which also gave the dough a slick, slimy feel.
8 How do you explain why whole wheat bread typically is denser than white bread?
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9 How do you explain why rye bread typically is denser than white bread?
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10 For which flours did the calculated percentage of gluten match the typical percentage of protein listed in the text?
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11 In general, how did the size of the gluten balls change with the amount of protein present in each flour?
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12 For which flours did the calculated percentage of gluten not match the typical percentage of protein listed in the text? Can you explain these discrepancies?
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13 How do you think forming a gluten ball from flour can help predict the suitability of the flour for use in bread baking?
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