a renewable raw material

Starch is abundant. All major agricultural crops contain starch. Colder climates favour potato growing, the tropics cassava, while grain varieties are grown all over the world. With sun and water as the main limitations, fifteen tons of starch dry mater can be achieved per hectare.

Modern techniques enable starch to be extracted from agricultural crops with high yield and extreme purity, making starch the most versatile raw material used within the food and chemical industries. The starch granule is a compact package of pure glucose polymer.

The purity and efficient moisture absorbing properties of starch have made it indispensable in the production of medicinal tablets and as a moisture regulator.

Polymer releases from the granule during cooking. At 60 ^oC, the polymer begins to hydrate, adding its viscosity and gelling power to the water. This is the way puddings are made in the home - just by using native starch. The food industry also employs native starch as a binder and thickening agent in snacks, meat products, sausages, etc.

Although native starch does have its industrial uses, most often industry requires the functionality of modified starch. The modification is achieved in one of two ways - either by the starch producer, who modifies the starch without disrupting the granules, or by the end-user who cooks and modifies the starch in a single step operation. The first method results in a granular product good for storage and the other in a ready-to-use paste. The two methods do not always act as a substitute for the other.

The single largest consumer of modified starch is the paper industry.

Starches are used as wet-end additives, as size press starches, as binders in coatings and as adhesives. Cationic starches provide retention at the wet-end and reduce the amount of pollutants released. Oxidised starch is a good film-forming product - a favoured material for coating and surface sizing. Thin boiling starches produced by acid or enzyme treatment are used as well.

Special starch produced by esterification or combined treatments are used in coatings, glues, the production of cardboard, etc.

The Stein Hall process of manufacturing corrugated cardboard employs both cooked and uncooked starch. Cooked starch adds viscosity while uncooked starch swells up as the cardboard liner passes the heating rolls, giving instant bond. Pre-swollen starch is used alone in no-carrier adhesives.

The process of drilling for oil uses starch in the suspension of excavated mud. During this process, starch is either employed alone or in combination with other stabilisers, e.g. xanthan gum. Within the textile industry, thin boiling starch has made a comeback in the competition with petrochemicals.

The addition of chemical groups to the starch chain improves the clarity and stability of the gel during cooking, mixing and freezing. These chemicals include propylene oxide, acetic acid, and metaphosphates. They form tailor-made hydrocolloids, which go into desserts, ice cream, puddings, wine gums, etc.

Starch is the cheap and reliable source of energy for the biochemical manufacturing of alcohol, enzymes and fine chemicals. When broken down by enzymes or acids it becomes the basic ingredient for producing glucose, fructose and sorbitol.