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FLOURS

QUESTIONS - p. 244

1. Should one type of flour be substituted for another on the basis of measure or weight? Why?

Wheat flours should be measured on the basis of weight to obtain the most accurate measure as differences in composition and milling procedures may cause variations in volume per weight of the different types of flour. Flours may vary in composition due to the particular strain of wheat, whether it is a hard or soft wheat. For example, hard wheat has a higher protein content which affects its weight per volume. Variations in composition results in the different types of flours having different densities. Bread flour is more dense than allpurpose flour, which is more dense than cake flour Different milling methods also result in variations in weight per volume. The greater the degree of extraction, the greater the weight of the flour per cup. Different particle size of the flour also leads to greater weight as the flour packs more, which can be seen with cake flour.

QUESTIONS - p. 246 (B)

1. In Part II, which of the batters were the thickest? Why?

The thickest batters were produced from the following flours, all-purpose and soy, both of which contain high amounts of protein. The thickness of the batters may be attributed mainly to the hydration capacity of the proteins in the flour. Hard wheat flours and soy flour,having more protein, are able to absorb more water and result in a thicker batter. The proteins, occurring in aggregates of starch and protein molecules, combine with water and separate into fibrils. The hydrated protein fibrils then separate out of the endosperm cell, carrying with them grains of starch. The batter thickens as the protein fibrils unite to form a network.

2. Which batters showed signs of elasticity? Why?

Flours containing gluten, such as all-purpose, whole wheat, and gluten, showed elasticity. The hydrated gluten-forming proteins interact and form a continuous gluten matrix which has elastic and stretchable properties.

3. What is gluten? How is it formed?

Gluten, the protein complex formed when wheat flour is manipulated with water, comprises two fractions. Gliaden, is soluble in 70% alcohol and is characterized by being sticky and fluid. Glutenin is insoluble in alcohol, and is characteristically very elastic. Glutenin molecules are fibrous in nature whereas gliaden molecules are more elliptical. In order for the gluten complex to form, the wheat flour must be manipulated together with water. Manipulation of the hydrated flour particles results in the hydrated protein fibrils being moved past each other so that they may bond together to form gluten. Several different types of proteinprotein interactions occur. The high concentration of asparagine and glutamine present in the proteins results in numerous amide groups being available for H bonding. The low net charge on the molecules favors Van der Waals bonds, and the presence of cysteine results in both intramolecular and intermolecular disulfide bonding. In this way different polypeptide chains can be linked together.

4. What are the characteristics of a dough containing gluten, before baking?

Before baking the dough is viscous and elastic.

5. How does the baked gluten ball differ from the unbaked? Why?

After baking, the size of the gluten ball is increased several fold, due to the ability of gluten to stretch and the pressure of the expanding gases. As the confined gases and steam expand, the gluten stretches and holds in those gases. The resulting increase in volume is maintained until the temperature becomes hot enough to coagulate the proteins, which gives the gluten ball its set structure.

6. What is the role of gluten in flour mixtures?

The role of gluten is:
1) to provide structure
2) to retain expanding gases and steam during baking
3) to give dough its viscoelastic properties, which allows dough to formed into different shapes.
The first two functions are illustrated in the baking of gluten balls.

7. Do all flours form gluten? Explain.

In order to form glutin, flours must contain the gluten forming proteins, glutenin

and gliadin. It is these proteins that form the gluten matrix as the flour is hydrated and manipulated. Wheat, rye and triticale flours do form gluten. Rice, soy, potato and corn flours do not form gluten, although they do contain other types of protein.

QUESTIONS - p. 246 (IV)

1. What is the effect of sugar and fat on gluten formation?

Both sugar and fat limit the amount of gluten that can be developed in a flour. Sugar does this because it is more hydroscopic than flour, thus limiting the amount of water available for hydration of the glutenforming proteins. Fat coats the flour particles and thus prevents the water from making contact with them. Fat is more effective at inhibiting gluten formation than sugar.

2. Account for the difference in amounts of water needed to form a dough.

The amount of water necessary to make a dough depends on the type of flour used and the other ingredients added to the flour. Hard wheats have a greater flour holding capacity. The addition of fat to the flour before the addition of water decreases the amount of water that can be absorbed. Oil coats the flour particles very well so that very little water can be absorbed which results in a very tender dough with little elasticity. The addition of fat also coats the flour particles, but not to the same degree so that more water can be absorbed by the flour particles. The additon of sugar does not greatly affect the amount of water necessary to make a dough as compared to flour only.