Facts and figures about starch
It consists of two types of molecules: linear and helical amylose as well as branched amylopectin. Depending on which plant the starch is obtained from, it consists of 20 to 25 % amylose and 75 - 80 % amylopectin.
Which plants is starch obtained from?
In Europe, mainly corn starch, wheat starch and potato starch are manufactured. Rice and tapioca are the main sources of starch in other regions. The plant-based starting materials are initially ground to release the starch. This is then ‘washed’ out of the cells and isolated by means of filtration and centrifugation. The last step involves drying the starch.
Properties of starch
Starch has one particularly important characteristic: as a thickening agent. When a mixture of water and starch is heated, the starch binds the water and swells. This creates a starch paste which serves as a thickening agent. Potato starch, corn starch and wheat starch all have different thickening properties. Besides gelatinised gluten, starch paste is the most important ingredient in bread and rolls. At low temperatures, the gelatinised starch gradually becomes viscous again due to the fact that the amylase in the starch is not as effective at binding water as amylopectin. This effect is known as retrogradation and occurs, for example, when bread goes stale.
Uses of Starches
Native and modified starches are used as an ingredient in food products, on the one hand, and for technical purposes (in the textile, paper, cosmetics, pharmaceutical and construction industries), on the other.
- Native starch is a powder obtained from plants containing starch. It is used as a thickening agent and a stabilizer. Good examples of this include custard, desserts, sauces and many forms of instant foods.
- Modified starches are obtained from native starches as a result of physical, enzymatic or chemical processing methods. Wet and dry chemical processes, drum drying and extrusion methods are all used. The properties of native starch such as its freeze-thaw stability, acid or alkali resistance or even its shear stability can be changed by means of these processes. Depending on the raw materials used starch is used for different applications. Native and modified starches can, for example, be used as ingredients in the production of foodstuffs, but also for technical purposes (in the textile, paper, cosmetic, pharmaceutical and construction industries).
- Starch saccharification products are formed by separating starch into its constituent sugar components. In this way, sugar can be obtained not only from sugar beet but also from starch-rich plants such as corn or potatoes. Starch saccharification products are largely used for sweetening carbonated soft drinks, ice cream, jams, confectionary, etc
What nutritional role does starch play?
Besides proteins and fats, carbohydrates also constitute a major source of human nutrition and energy. Carbohydrates consumed in the course of our daily nutrition are either broken down or converted into glucose in the human body. Glucose is the human body’s preferred source of energy and is particularly important for the brain, renal medulla and for the formation of red blood cells.
According to the German (DGE), Austrian (ÖGE) and Swiss (SGE/SVE) nutritional societies, 50 - 55 % of our daily energy requirements should be sourced from carbohydrates, with the majority of this being from complex carbohydrates such as starches. Complex carbohydrates, which are mainly found in potato and cereal products, are taken up by the body slower and have a positive impact on the release of insulin and the increase of blood sugar levels.
The relatively difficult to digest starches also contained are referred to as dietary fibre. These starches cannot be broken down by human enzymes but are partially broken down by bacteria in the large intestine. Dietary fibre serves a number of important roles in the digestive tract and also has positive impacts on our metabolism.