Uses of Starch and Fibre

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Starch Starch is easy to extract from plants. This is because it is in granules, which do not dissolve in water, but can be washed out. In wheat, the protein remaining is gluten, which is a rubbery mass. The elastic properties of gluten are vital in bread making, but are not used much in industry. Starch has other uses however. It is found in a wide range of products including adhesives, paints, textiles, plaster, insulating material and toiletries such as conditioners, mousses, sunscreens and anti-perspirants. Thickening: When starch granules are heated in water they suddenly swell, absorb water, and thicken the liquid. This process is known as ‘gelatinisation’, a process that is basis of both wallpaper past and custard. Stiffening fabrics: The stiffening of cloth or paper by starch is known as ‘sizing’, and enormous amounts of starch are used in paper coatings and cloth treatment. A starch mixture is applied to the surface and is gelatinized and then cooled, allowing bonds to form between the starch molecules. The addition of water reverses the stiffening. This reversal is called ‘plasticisation’. This reversible behaviour is very useful, since by the addition of a little water and heat, the shape can be changed many times. Super absorbents: If starch is chemically cross-linked before it is gelatinised then particles are formed which can be dried. When rehydrated these particles can take up large amounts of water, an example of this is the super-absorbents in nappies. Starch foam: The temperature a which starch gelatinises depends on the amount of water present. When the water content is less than 10% the process occurs at a much higher rate. If the pressure is raised at the same time, the starch forms a plastic mass. Examples of this include popcorn and ‘packaging peanuts’ (starch-based packaging). This starch-based packaging can now be used

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