Amylose is a linear polysaccharide composed mainly of glucose. It is found, to the extent of about 20-30% in starch which is the primary form of storage of carbohydrates in plant tubers and seeds, together with the prevalent Amilopectin, with 70-80%.

The amylose content is considered the determining factor for the processing, cooking and pleasantness of cooked rice (Oryza sativa L.) cooked and is directly linked to the volume, water absorption and final compactness of cooked rice (1). In general, the amylose content in milled rice is classified into five classes:

• waxy (0-2%)
• very low amylose (3-9%)
• low amylose (10-19%)
• intermediate amylose (20-24%)
• high amylose content (over 24%)

The low amylose content is associated with a cohesive, tender and glossy rice. A high amylose content is associated with a dry, stable, soft cooked rice with well separated grains (2).

The name defines the structure of the molecule:

• Amylose comes from the Greek word "amilon" which means starch. It is a type of polysaccharide consisting of glucose units linked together by α(1 4) glycosidic bonds.

The synthesis process takes place in several stages:

• Glucose production. Plants produce glucose through the process of photosynthesis. In this treatment, sunlight, water and carbon dioxide are used to produce glucose and oxygen.
• Glucose activation. Glucose molecules are activated by being converted to glucose-1-phosphate. This reaction is catalyzed by the enzyme glucochinase.
• Conversion to ADP-glucose. Glucose-1-phosphate is then converted to ADP-glucose (adenosine diphosphate glucose) in a reaction catalyzed by the enzyme glucose-1-phosphate adenyltransferase.
• Polymerization. ADP-glucose molecules are then polymerized to form amylose. This reaction is catalyzed by starch synthase bound to granular enzymes. The enzyme catalyzes the formation of α(1 4) glycosidic bonds between glucose units, forming a linear chain.
• Formation of starch granules. Amylose molecules are then packaged into starch granules within plant cells. These granules also contain amylopectin, the other component of starch.

What it is for and where

Cosmetics

Humectant. Hygroscopic compound used to minimise water loss in the skin and to prevent it from drying out by facilitating faster and greater absorption of water into the stratum corneum of the epidermis.  The epidermis is the most superficial of the three layers that make up human skin (epidermis, dermis and hypodermis) and is the layer that maintains hydration in all three layers. In turn, the epidermis is composed of five layers: horny, the most superficial, granular, spinous, shiny, and basal. Humectants have the ability to retain the water they attract from the air in the stratum corneum and have the function of moisturising the skin. They are best used before emollients, which are oil-based.

• Molecular Formula: C₁₈H₃₂O₁₆
• Molecular Weight: 504.438 g/mol
• CAS: 6401-81-6  9005-82-7  1109-28-0
• EC Number: 214-174-2 232-685-9

Synonyms:

• Maltotriose
• α-D-Glc-(1→4)-α-D-Glc-(1→4)-D-Glc, O-α-DD-Glucopyranosyl-(1→4)-O-α-D-glucopyranosyl-(1→4)-D-glucose
• alpha-maltotriose
• alpha-D-glucopyranosyl-(1->4)-alpha-D-glucopyranosyl-(1->4)-
• alpha-D-glucopyranose
• Amylotriose
• UNII-7TDQ74Y18L
• alpha-D-Glcp-(1->4)-alpha-D-Glcp-(1->4)-alpha-D-Glcp
• Triomaltose
• Amylose from potatoes
• SCHEMBL35350

References________________________________________________________________________

(1) Juliano B.O. Rice Chemistry and Technology. American Association of Cereal Chemists; St. Paul, MN, USA: 1985. Criteria and Test for Rice Grain Quality; pp. 443–513.

(2) Juliano B.O. A simplified assay for milled-rice amylose. Cereal Sci. Today. 1971;16:334–340