Fine Structures and Physicochemical Properties of Starches from Chalky and Translucent Rice Kernels

Abstract

This work compared the molecular structures and physicochemical properties of starches obtained from chalky and translucent kernels of six rice cultivars. Starch samples were prepared according to a modified alkali steeping method. Crystallinity, pasting characteristics, and thermal properties were studied by X-ray diffraction, rapid viscosity analysis, and differential scanning calorimetry, respectively. Starch molecular size fractions (amylopectin, amylose, and intermediate material) were estimated by high-performance size exclusion chromatography, and the chain length profiles of isoamylase-debranched amylopectin were evaluated by high-performance anion-exchange chromatography with pulsed amperometric detection. Starches from chalky kernels contained less amylose (more amylopectin) and more short branch-chain amylopectin (less long branch-chain amylopectin) compared with the translucent kernel starches. Differences in starch structural features significantly correlated with observed variation in grain translucency, starch X-ray diffraction patterns, thermal properties, and pasting characteristics. Starch synthesis in chalky kernels may slightly favor glucan chain branching over chain elongation.

Endosperm Structure of White-Belly and White-Core Rice Grains Shown by Scanning Electron Microscopy

“…In the amylopectin fine structure, Lisle et al (2000) found no significant differences between chalky and translucent grains in the amount of high or low molecular weight glucans in the amylopectin fraction. By contrast, Patindol and Wang (2003) reported that chalky grains had shorter average chain length of amylopectin, higher percentage of short amylopectin branch chains, and lower percentage of long branch chains. The disagreement may be partially associated with the subtle difference in amylopection fine structure as well as the analytical method.…”

“…From analysis of the sucrose level in inferior and superior spikelets, Lisle et al (2000) suggested that chalkiness was not due to insufficient vascular supply of metabolites like sucrose and amino acids, but was more likely related to metabolic events within the developing grain that utilize carbon in sucrose for starch deposition. Patindol and Wang (2003) reported that chalky grains had shorter average chain length of amylopectin, which indicated that the formation of chalkiness might be associated with interruption in the step of chain length elongation. These two studies offer novel perspective for understanding the physiological reasons for chalkiness.…”

QTLs and analysis of the candidate gene for amylose, protein, and moisture content in rice (Oryza sativa L.)

“…The QTLs controlling the composition of various protein fractions could be at the same chromosome locus. Patindol and Wang (2003) detected 18 chromosome portions for 19 single amino acids, with that located at the base of chromosome 1 being somewhat a stronger QTL bunch, comprising 19 single quantitative trait loci. There is a vast co-occurrence among the qualitative trait loci and the loci responsible for amino acid metabolic pathways, nitrogen absorption and transfer, and protein biosynthesis (Patindol and Wang 2003).…”

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“…(González et al, 2004). Patindol and Wang (2003) studied the physicochemical properties of three nonwaxy, long-grain rices and found that different amylopectin structures could affect rice functionality, for example, the gelatinization, retrogradation and pasting behavior. Rice with an amylose content of 7.8% in comparison with four other rice varieties with 15.6-18.9% amylose content.…”