Complex Polysaccharides in Food Science - Essay Example

The foaming power of albumen is important in providing a raise (leavening) and lightness in foods such as meringues and angel cakes.  

An example of a food foam system is angel cakes.

1. Give a brief description of the functional components in a food emulsion.

A food emulsion has two components.  The liquid component, which is in the form of droplets suspended in the other component, is known as the dispersed, discontinuous, or open phase.  The other phase is called the continuous or closed phase.

For instance, when oil and water are mixed together vigorously, the oil may be dispersed in the water, or the water may be dispersed in the oil.  In an ‘oil in water emulsion’, oil forms droplets in water (oil dispersed in water), and in a ‘water in oil emulsion’, water forms droplets in oil (water dispersed in oil).

1. What are the main components in cow’s milk that can be turned into cheese?  Which of these has the key role in stabilizing the others?

Proteins, fat, and lactose in the milk help in the processing of milk into cheese.  Caseins that form about 80% of the protein play a key role in stabilizing the others.

1. What are the main differences between climacteric and non-climacteric fruits with respect to their ripening?

Fruits can be divided into climacteric and non-climacteric types based on the pattern of respiration during the ripening period.  Climacteric fruits include apples, bananas, pears, melons, and avocados which have a distinct ripening phase.  Non-climacteric fruits include citrus fruits, grapes, strawberries, and pineapple which have no distinct ripening phase. 

The two classes respond to ethylene quite differently.  If immature climacteric fruits are treated with ethylene, the onset of the climacteric and the associated ripening changes is hastened, but the overall pattern of respiration remains unchanged.  If non-climacteric fruits are treated with ethylene, the rate of respiration is rapidly increased which leads to changes in color through loss of chlorophyll, increases in simple sugars, and loss of acids.  For example, oranges lose chlorophyll

1. Describe the components of wheat flour that form gluten during bread making and explain the mechanism by which they are believed to do this.

Wheat proteins are divided into gluten proteins (generally about 80 to 85% of total wheat protein) and non-gluten proteins (about 15 to 20% of total wheat protein).  It is the gluten proteins that largely determine the breadmaking performance of wheat flour.  Wheat gluten proteins have the unusual property to form a visco-elastic mass after hydration.  When kneading/mixing the flour with water, gluten proteins enable the formation of a cohesive visco-elastic dough that is capable of holding gas produced during fermentation and oven rise, resulting in the typical fixed open foam structure of bread after baking.  Although the dough's rheological properties essential for breadmaking are largely determined by the wheat gluten proteins, interactions of the gluten protein matrix with other flour components like flour lipids, and non-gluten proteins, may affect its rheological properties.  Wheat gluten rheological properties can be modified further by the addition of oxidants, reducing agents, or proteases that directly change gluten proteins or by the addition of lipids/emulsifiers or hemicelluloses that can modify gluten protein interactions.

Wheat flour breadmaking performance is linearly related to flour protein content and thus with gluten protein content.  This is so because the gluten protein fraction increases much more than the non-gluten protein fraction with increasing grain protein content.  Thus, a high quantity of gluten proteins is important.  However, the linear relationship between protein content and breadmaking performance depends on the wheat variety, suggesting that gluten protein ‘quality’ is also relevant.

An adequate balance of viscosity and elasticity/strength is required for quality breadmaking.  Insufficiently elastic gluten leads to low bread loaf volume.  Increased elasticity leads to higher loaf volume, but too elastic gluten impedes the expansion of gas cells leading again to lower loaf volume.  Dough elastic/strength properties are ascribed to the glutenin polymers.  The large size of the latter provides continuity to the dough system.  The elasticity of glutenin is believed to depend on the reversible stretching of an energetically more favorably folded glutenin conformation.  Also, the ratio of monomeric gliadin to polymeric glutenin determines the balance between dough viscosity and elasticity and therefore affects gluten protein quality.