up to two million glucose molecules. A section of its structure is shown below:
IV/V - 3 (of 3)
The starch found in food often contains a mixture of these two molecules, but the amylopectin usually
accounts for the majority of the starch (between 70 and 85%). The exact ratio of amylose to
amylopectin will depend on the food source from which the starch is extracted, and since the amylose
and amylopectin molecules behave in slightly different ways, starches derived from different plan
origins will behave slightly differently.
The primary culinary role of the starches is as thickening agents. In the presence of water or any
liquid, these long starch molecules will evenly disperse themselves throughout the liquid, and will
therefore reduce the ease with which the water molecules contained can move around each other.
The liquid will therefore “flow” less easily, and will become thicker. If the appropriate conditions, these
starch molecules will join together to form an extensive network, which can actually traps the water
molecules, making the liquid slightly solidify or “gel”. This is similar to the way that denatured proteins
can be used to retain the water in food systems and help keep food sources more “juicy”. Over time,
the network will become stronger and stronger as more bonds are made and the network gel will start
to squeeze out water in a process called synergesis.
Starch is derived from plant tissue, where the starch molecules are organised into small structures
called granules, in which the starch granules are very tightly bonded together and this structure can
only be disrupted and the starch released in the presence of moist heat. In starch granules, the
amylose and amylopectin molecules are held closely together as granules. Microscopes have shown
us that these starch granules contain circular layers of amylopectin and amylose molecules held
together by hydrogen bonding.
The more amylose present in the starch granules, the more strongly the granule will be held together,