Shear flow properties of carbon fibre-filled polyethylene melts

Abstract

Waxy cassava starch (WS) from a spontaneous mutation offer enough advantages to encourage the development of commercial varieties. However, breeding work is limited because only one source of WS was available. This article reports the discovery of five new sources of WS which were compared with commercial (CC) and high amylose (HA) cassava starches (19.9 and 30.2% amylose, respectively). Waxy starch gels were considerably clearer and had higher solubility and swelling power than those from CC. Pasting temperature and peak viscosity in WS were higher (68.5 °C and 1149 cP) than in CC (64.2 °C and 993 cP). No retrogradation or syneresis could be detected in refrigerated gels or after freeze/thaw cycles in any WS gel. Average λmax for WS, CC and HA were 540.2, 591.3 nm, and 607.0 nm, respectively. Amylopectins from WS displayed M¯w between 271 × 106 and 551 × 106 g mol−1, R¯G ranged between 229 and 298 nm and νG values ranged between 0.38 and 0.40 (between the sphere and the random coil). The apparent density distributions in all WS suggested close densities and branching structure. The corrected average number of glucosyl units in a linear chain averaged 21.2 in WS and 23.1 in CC. Amylopectins from WS showed a slightly more branched structure (average 4.8%) than in CC (average 4.3%), but lower than in HA (7.0%). WS exhibited larger average granule size (15.9 μm) compared with CC (14.3 μm). New sources of WS will contribute the breeding efforts to develop successful commercial varieties.