【Reading】あみろーす

【English Name】Amylose

Amylose, in which α-glucose units are linked in a chain by α1→4 glycosidic bonds, is a polysaccharide counted as one of the two major components composing starch. Its structure contrasts with highly branched amylopectin; amylose takes a form close to a linear chain—yet it is not a purely linear molecule, as it has been revealed that several to twenty-odd branch points are scattered within a single molecule.

The proportion of amylose in starch is said to be roughly 20% as a standard value, and this ratio greatly influences the stickiness of rice and wheat. The trend is that the lower the amylose content, the higher the stickiness; sticky varieties are classified as the glutinous (mochi) type and less-sticky varieties as the non-glutinous (uruchi) type.

From the standpoint of shari, amylose content is a core indicator governing the rice's viscosity and the texture in the mouth. Because what sushi rice requires is moderate grain definition and just the right stickiness, varieties with somewhat lower amylose content even among the non-glutinous type tend to be valued. The grounds for saying that varieties showing a low-amylose tendency, such as Koshihikari, suit vinegared rice lie precisely in this point.

Showing a blue-purple color upon reaction with iodine solution is a property unique to amylose, clearly distinguishable from amylopectin, which exhibits a red-purple color. Incidentally, its number-average molecular weight falls roughly in the range of 500,000 to 2,000,000, a considerably lower value compared with amylopectin.