What are starches?

Starches are extracted from plants, particularly cereal crops. They are polysaccharide carbohydrates made up of glucose chains. The chains are either amylopectin (branched chain) or amylose (straight chain). Starches from different origins have varying levels of these two components. Typically, starches contain 70% - 80% amylopectin and 20% - 30% amylose. Starches with levels outside these parameters usually exhibit special properties.

What are the properties of starch?

The properties of an individual starch are dependent upon the amylopectin/amylose ratio. After hydration & heating the two components exhibit different properties :-

Amylopectin	:  Forms viscous solutions
Amylose	:  Forms firm gels

As the level of amylose increases, so does the gel strength, of a particular starch, but also the risk of syneresis.

Won't any old starch do?

A specific starch must be selected for a specific application. If thickening properties are required, a product high in amylopectin should be selected. For gel strength, select a starch rich in amylose.
Typical amylose levels :-

Tapioca	:  17%
Rice	:  20%
Potato	:  22%
Maize	:  25%
Wheat	:  25%
Pea	:  35%

In what forms are starches available?

Starches are available in three main forms :-

1. Native :   The starch after it has been extracted and purified.
2. Pre-gelatinised :   Native starch which has been heated to give cold solubility & functionality.
3. Modified :   Processed to modify the properties of the native starch. They are not genetically modified.