| Abstract: | Cassava and rice amylopectins and their ?,β‐limit dextrins were debranched and the unit chain compositions were analyzed by gel permeation chromatography and high performance anion‐exchange chromatography. The content of amylose and super‐long amylopectin chains was 15.5‐15.6% and 0.8‐1.2% in cassava and 15.1‐18.7% and 3.4‐8.6% in rice starches, respectively. The internal unit chain profiles of the amylopectin samples were obtained from the ?,β‐limit dextrins. Short B‐chains were subdivided into a major group (BSmajor) with a degree of polymerization (DP) of 8‐25 and a minor group of “fingerprint” B‐chains (Bfp) with DP 3‐7. Cassava and rice amylopectins possessed different amounts and patterns of Bfp‐chains. The rice samples contained higher amounts of Bfp‐chains, which suggested larger size of its clusters when compared with cassava. The content of the shortest “fingerprint” A‐chains (Afp) was also variable, especially between the rice cultivars. The position of the internal chains in the original amylopectin chain profile was traced. The reconstructed B‐chain profiles fitted well with the original profiles. This implied that most of the B‐chains carried external chain segments of similar lengths, which corresponded to the experimentally measured average length. |
