Structures of branched molecules of amyloses of various origins, and molar fractions of branched and unbranched molecules

✍ Scribed by Yasuhito Takeda; Susumu Hizukuri; Chieno Takeda; Ayako Suzuki

• Publisher: Elsevier Science
• Year: 1987
• Tongue: English
• Weight: 361 KB
• Volume: 165
• Category: Article
• ISSN: 0008-6215
• DOI: 10.1016/0008-6215(87)80089-7

✦ Synopsis

Pure amyloses obtained from various starches contain limited numbers of branch linkages and are mixtures of branched and unbranched moleculesl-14, although amyloses are defined as unbranched molecules. However, amyloses of various origins have been characterised generally without separation of the branched and unbranched molecules due to the lack of an effective method for their separation. The aqueous leaching of starch granules leads to only partial separation2-4J5. In this study, we investigated in detail the structures of beta-limit dextrins of amyloses of various origins in order to elucidate the structures of branched components of the amyloses. In addition, the molar fractions of the branched and unbranched molecules of the amyloses have been determined.

Table I shows the properties of 9 amyloses from cereals, seeds, roots, and tubers. These specimens showed similar values of iodine affinity, blue value, and A _., and were confirmed to be free from amylopectin by gel chromatography6JJa. The corn, wheat, kuzu, and sweet-potato amyloses were characterised in this work, and the others previously6sJ0-14. Th e molecular sizes of these amyloses ranged from d.p. 960 (corn) to 3280 (sweet potato), and the cereal amyloses appear to be smaller molecules than other amyloses. These amyloses were hydrolysed to 75 -91% with beta-amylase, and the average chain-lengths (c.1.) ranged from 270 (wheat) to 525 ( na g aimo). Most amyloses comprised 3-5 chains per molecule on average, but the tapioca and sweet-potato amyloses had 7.9 and 9.8 chains, respectively. These chains were joined by a-(1+6) linkages, since the amyloses were completely degraded with beta-amylase and pullulanase. These properties