Molecular Structure of Selected Tuber and Root Starches and Effect of Amylopectin Structure on Their Physical Properties

The objectives of this study were to characterize starches isolated from potato, canna, fern, and kudzu, grown in Hangzhou, China, for potential food and nonfood applications and to gain understandings of the structures and properties of tuber and root starches. Potato and canna starches with B-type X-ray patterns had larger proportions of amylopectin (AP) long branch chains (DP L37) than did fern (C-type) and kudzu (CA-type) starches. The analysis of Naegeli dextrins suggested that fern and kudzu starches had more branch points, alpha-(1,6)-D-glycosidic linkages, located within the double-helical crystalline lamella than did the B-type starches. Dispersed molecular densities of the C- and C-A-type APs (11.6-13.5 g/mol/nm(3)) were significantly larger than those of the B-type APs (1.4-6.1 g/mol/nm(3)) in dilute solutions. The larger proportion of the long AP branch chains in the B-type starch granules resulted in greater gelatinization enthalpy changes (Delta H). Retrograded kudzu starch, which had the shortest average chain length (DP 25.1), melted at a lower temperature (37.9 degrees C) than the others. Higher peak viscosities (550-749 RVU at 8%, dsb) of potato starches were attributed to the greater concentrations of phosphate monoesters, longer branch chains, and larger granule sizes compared with other tuber and root starches.