flour - FLOUR Introduction The proteins in flour have...

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Unformatted text preview: FLOUR Introduction The proteins in flour have unique functional properties. These properties and the nutritional importance of flour have made bread a staple in man's diet throughout history. In recent years, extensive research and development work has taken place to more clearly identify the unique functional properties and the physical and chemical properties of flour proteins. Before discussing the various food products made with flour, we need to understand the functional properties of flour proteins. Flour Proteins The average composition of flour is given in Table 1. Based on solubility, the classification of flour proteins is given in Table 2. The composition of cereal proteins with regard to solubility is given in Table 3. These classifications are usually considered sub-groups of two major classifications, gluten (dough forming) proteins and non-gluten proteins. For wheat flour this grouping is shown in Figure 1. The dough forming proteins, glutelins and prolamines, are the components that impart the common structural and functional characteristics to bread. When hydrated, glutelin and prolamine form gluten. The important properties of gluten include the following: 1) Ability to form a visco-elastic mass. With a certain amount of mixing, hydrated gluten develops into a firm, resilient, and adhesive substance which is insoluble in water and exhibits both viscous and elastic properties. 2) Ability to form films. When the formed visco-elastic mass is further mixed or kneaded, it develops into a continuous three-dimensional web of films. Solid particles as well as gas bubbles may thus be enveloped throughout this continuous gluten mass. 3) Thermosetting ability. When heated above 85 o C, the hydrated gluten mass coagulates irreversibly without loss of its unique structural order, yielding a firm, non-sticky, moist, clean cutting and resilient gel. 3-1 Table 1. Basic Composition of Flour. FLOUR Component Average Composition Water 12% Protein 7-13% Fat 0.8-2% Carbohydrate 71-80% Ash 0.3-2% Table 2. Solubility Classification of Simple Proteins in Cereal Seeds. Albumins Soluble in water or dilute salt solutions Globulins Insoluble in water, soluble in salt solutions Prolamines Insoluble in water and absolute alcohol, soluble in 80% alcohol (present in cereal seeds only) e.g. zein from corn, gliadin from wheat, hordein from barley Glutelins Insolube in neutral solvents. Soluble in dilute acids or bases (present in cereal seeds only) e.g. Glutenin from wheat, Oryzein from rice _____________________________________________________________ 3-2 Table 3. COMPOSITION OF CEREAL PROTEINS (% ON A DRY MATTER BASIS).Table 3....
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This note was uploaded on 05/03/2009 for the course FST 101B taught by Professor Charlesshoemaker during the Winter '08 term at UC Davis.

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flour - FLOUR Introduction The proteins in flour have...

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