Structure-Functionality Changes in Starch Following Rough Rice Storage

Abstract

The molecular-level features of starch in relation to the changes in rice functionality during storage are not yet fully elucidated. This work investigated the effects of rough rice storage conditions on starch fine structures and physicochemical properties. Dried rough rice samples (medium-grain Bengal and long-grain Cypress) were stored at 4, 21, and 387C in temperature-controlled chambers and then periodically removed and evaluated after 1, 3, 5, 7, and 9 months. Flour (powdered head rice) and starch (extracted from head rice by alkali steeping) samples were evaluated for pasting and thermal properties. High-performance size-exclusion chromatography and high-performance anion exchange chromatography were used to characterize starch molecular size and amylopectin chain-length distribution, respectively. Significant changes in starch fine structure were observed primarily on the 387C lots, and to some extent on the 217C lots. The decreased amylose: amylopectin ratio, shortened amylopectin average chain length, and the shift in chain-length distribution to shorter branch chains were implicative of molecular-level starch degradation. The flour and starch samples showed inconsistent trends in pasting and thermal properties, thus suggesting the role of not only starch but also its interaction with non-starch components in rice aging.

Chemometric Analysis of the Gelatinization and Pasting Properties of Long‐grain Rice Starches in Relation to Fine Structure

“…The role of amylose and amylopectin in the gelatinization and pasting properties of rice starch has been widely studied [2,[5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Starch swells irreversibly and its crystalline structure collapses when heated in excess watera phenomenon known as gelatinization.…”

“…Starch swells irreversibly and its crystalline structure collapses when heated in excess watera phenomenon known as gelatinization. Starch swelling is a property of amylopectin [5], whereas, amylose has been known to restrict it [5][6][11][12][13][14][15][16]. Restricted starch granule swelling results in a lower peak paste viscosity based on measurements with a Brabender Viscoamylograph or a Rapid Visco Analyser [6][7][8][9][10][11][12][13][14][15][16][17].…”

“…Starch swelling is a property of amylopectin [5], whereas, amylose has been known to restrict it [5][6][11][12][13][14][15][16]. Restricted starch granule swelling results in a lower peak paste viscosity based on measurements with a Brabender Viscoamylograph or a Rapid Visco Analyser [6][7][8][9][10][11][12][13][14][15][16][17]. Paste breakdown correlates positively with the proportion of short amylopectin chains, negatively with long chains [6][7][12][13][14], and also negatively with amylose content [6,14,17].…”

“…Restricted starch granule swelling results in a lower peak paste viscosity based on measurements with a Brabender Viscoamylograph or a Rapid Visco Analyser [6][7][8][9][10][11][12][13][14][15][16][17]. Paste breakdown correlates positively with the proportion of short amylopectin chains, negatively with long chains [6][7][12][13][14], and also negatively with amylose content [6,14,17]. Temperature and enthalpy of gelatinization as measured by differential scanning calorimetry correlate negatively with the amount of amylopectin short chains (DP6-12 or A chain), and positively with longer chains (DP12-24 or B1 chain) [6,9,12,[18][19].…”

Viscoelastic Properties and Physico-Functional Characterization of Six High Yielding Cassava Mosaic Disease-Resistant Cassava (Manihot Esculenta Crantz) Genotypes

“…Significant differences (P<0.05) existed amongst the varieties except for Broni bankye, Otuhia and Amakuma. Breakdown viscosity is the measure of the tendency of swollen starch granules to rupture when held at high temperatures and continuous shearing [32] and it is indicative of the stability of the starch on heating. Breakdown viscosities was significantly higher in the other cassava varieties studied than Sika (improved variety), which makes Sika very stable during heating.…”