Amylose and Amylopectine in rice

Starch molecules accumulate to form starch grains, which are visible in many plant cells, notably in storage organs such as the potato tuber, and in seeds of cereals and legumes.


In rice for example, amylose is found inside the microscopic granules, which make up a single rice grain. Amylopectin forms the crystalline or ice-like "skeleton" of these granules. Scientists think the amylose forms into long chain-like arrangements to fill up the spaces inside of the granule. The protein in rice grains is found in pockets between granules of starch. The cooking and eating characteristics of rice are influenced by the amount of amylose found in the grains. This is because the starch granules in the grain expand during cooking, forcing out the chains of amylose in a process scientists call leaching. As the cooked rice cools, the leached amylose chains line up, lock together and form a gel. When rice cools to room temperature or beyond, the chains of amylose crystallise. Generally, the higher the amylose content of rice, the firmer the cooked grain of rice will be. Some types of rice are between 25% and 30% amylose. These high amylose levels tend to make the rice cook firm and dry. Rice with a medium amylose content of between 16% and 22% usually cooks softer and the grains stick together more readily.

Back