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Molecular structure of starches from cassava varieties having different cooked root textures

Abstract
Starches from 12 cassava varieties with different cooked root texture; i.e. mealy, firm and mealy and firm, were investigated with a particular focus on aspects of molecular structures of amylose and amylopectin. Structural elements of amylopectin were essentially constant in terms of unit chain distributions and chain lengths. All cassava amylopectins displayed two distinct chain length peaks, at DP 40–46 and at DP 11–13, with a shoulder at DP 17–19, and average chain length (CL) of amylopectins was 17–20. A fraction of extra-long chains in the range of 0.24–1.78% was found. Amylose and amylopectin from four varieties with different textures of cooked root were isolated. Data from C-chain distributions indicated that the molecular size of amylopectin from M-hanatee (Hanatee), a locally adapted cassava variety, was 2.5–2.9 times smaller than those of the other varieties. Three of the four amylose samples, except that from M-hanatee, were very similar in average DP (4120–4390), chain length (530–550) and number of chains (7.1–7.5), and composed of nearly equal numbers of linear and branched molecules. The amylose from the M-hanatee variety showed a unique characteristic: it had smaller size (2050), shorter chain length (450), fewer chains (4.7) and a higher content of linear fraction (58%), when compared with other amyloses.

Keywords

Cassava starch; Molecular structure; Amylose; Amylopectin

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