Humans and their ancestors have always eaten starchy foods derived from seeds, roots and tubers. The practical use of starch products and perhaps of starch itself, developed when Egyptians, in the pre-dynastic period, cemented strips of papyrus together with starch adhesive made from wheat.
Starches are carbohydrates that are storage materials in the seed and roots of many plants. Corn, wheat, rice and other grains, as wee as potatoes and other rootlike vegetables, contain significant amount of starch.
Starch has a negligible osmotic pressure, which allows plants to store large reserves of carbohydrate without disturbing the cell’s water relations.
Starch is, made up of many units of glucose linked together in different forms. In the intestine, starch is broken down to glucose and utilized of energy.
Cooling (moist heat) causes starch grains to swell and rupture, thus converting starch to a form that is readily digested.
In the body, much of the glucose may be utilized directly as a source of energy, but some of it is converted into fat, the muscles utilizing fatty acids indirectly as fuel for energy. Excess carbohydrates not required for energy, when ingested (eaten) will be stored in the body as fat.
The starches important in foods are primarily of plant origin and exhibit the following properties:
1 They are not sweet
2 They are no readily soluble in cold water
3 They form pastes and gels in hot water
4 They provide a reserve source in plants and supply energy in nutrition
5 They occur in seeds and tubers as characteristics starch granules
When a suspension of starch granules in water is heated, the granules swell due to water uptake and gelatinize: this increase the viscosity of the suspension and finally, a paste of formed which, on cooling can form a gel.
Gelatinization process is characterized by the gelatinization temperature, above which the gelatinization of the starch suspension starts due to heat and moisture transfer phenomena.
Many starches particularly the cereal starches such as corn, sorghum and wheat and also some of the flours such as wheat and potato flours, have a characteristics flavour which is caused by material other than carbohydrate. The flavours appear to be due to the oxidation of lipids present catalyzed by traces of copper and iron.
Because of their viscosity, starch pastes are used to thicken foods, and starch gels, which can be modified by sugar or acid are used in puddings.
Both pastes and gels can revert changes in food textural properties. Partial breakdown of starches yields dextrin, which are intermediate in chain length between starches and sugars and exhibit other properties intermediate between these two classes of compounds.
Many cooks use starch for such diverse properties as thickening gravies and soups, making a sweet pudding or dusting pastry before cooking.
For such purposes powdered starch in packet form in soften in direct competition with the wheat flour found in nearly every British and American and many Continental household, whilst in the latter potato starch or, quite often potato flour is in customary use.
Starch in General