Search

A series of 17 samples represented a diverse collection of different starch granules from different plants. The amylose content ranged from 0% to 28% and the crystallinity was established to represent A, B and C allomorphic types. The amylopectin components were isolated and their unit chain distributions analysed by anion-exchange chromatography. The internal unit chain profiles were obtained from the φ,β-limit dextrins. The internal profiles possessed two major fractions of short and long B-chains. The long B-chains were divided into two subgroups also found in the profiles of the whole amylopectins. The short, internal B-chains contained also two subgroups in all samples, of which one was a major group at DP 8–25, and the other was a minor group at DP 3–7. On the basis of the internal chain distribution profiles of (i) the long chains, reflecting the interconnection of clusters, and (ii) the short chains, reflecting the internal structure of the clusters, the samples were divided into four structural groups with typical characteristics. It was found that the unit chain profiles of the whole amylopectins could be divided into the same characteristic groups. The positions of the internal unit chains were theoretically traced into their original lengths in the profiles of the whole amylopectins. It was concluded that A-chains generally overlap with the shortest B-chains at DP 13–23, which coincided with fraction fb 1 of the periodic intervals described by Hanashiro et al. [Hanashiro, I., Abe, J.-i., & Hizukuri, S. (1996). Carbohydrate Research, 283 , 151–159].

The extent of irrigation of crops in the field not only affects crop yield but also the functionality of the harvested product. This irrigation effect severely affects the processing response of starch harvested from Cassava and leads to industrial quality control problems. In this paper we show how the NMR transverse proton relaxation spectrum is a sensitive probe of the effect of irrigation on cassava starch functionality. The results suggest that increased irrigation results in a looser packing of the amylose and amylopectin chains in the cassava starch granule that facilitates their plasticization and gelatinization.

The influence of reaction parameters on the carboxymethylation of rice starches with different amylose contents was investigated. Rice starches with varying amylose contents showed various degrees of susceptibility to the reaction conditions. The maximum degree of substitution (DS) for all three rice starches was obtained under similar reaction conditions which involved a reaction medium consisting of isopropanol–water at the ratio of 90:10, a molar ratio of NaOH:AGU at 1.5 and a reaction temperature and time of 40 °C and 3 h. Under these conditions, the DS for all rice starches was similar; however, when the reaction was performed under conditions using lower NaOH concentration, the effect of starch types on the DS was observed. The results could be explained in terms of the granular/structural features of the different rice starches, their degrees of granular swelling as influenced by the reaction conditions and the accessibility of the etherifying reagents to starch molecules.