Normal Rice Starch Research Articles

The effects of chain-length distributions on starch-related properties in waxy rices

Normal rice starch consists of amylopectin and amylose, whose relative amounts and chain-length distributions (CLDs) are major determinants of the digestibility and rheology of cooked rice, and are related to metabolic health and consumer preference. Here, the mechanism of how molecular structural features of pure amylopectin (waxy) starches affect starch properties was explored. Following debranching, chain-length distributions of seven waxy varieties were measured using size-exclusion chromatography, and parameterized using biosynthesis-based models, which involve breaking up the chain-length distribution into contributions from five enzyme sets covering overlapping ranges of chain length; structure-property correlations involving the fifth set were found to be statistically significant. Digestibility was measured in vitro, and parameters for the slower and longer digestion phase quantified using non-linear least-squares fitting. The coefficient for the significant correlation involving amylopectin fine structure for the fifth set was −0.903, while the amounts of amylopectin short and long chains were found to dominate breakdown viscosity (correlation coefficients 0.801 and − 0.911, respectively). This provides a methodology for finding or developing healthier starch in terms of lower digestion rate, while also having acceptable palatability. As rice breeders can to some extent control CLDs, this can help the development of waxy rices with improved properties.

The Effects of D‐Allulose on the Gelatinization and Recrystallization Properties of Starches from Different Botanical Sources

AbstractD‐allulose (Alu), a rare sugar, has proven to be a low‐caloric sugar with potential health benefits. Previous studies have reported that compared with sucrose (Suc), Alu suppresses an increase in gelatinization temperature and retards retrogradation in glutinous rice starch. This study investigates the effect of Alu on gelatinization, water activity, and recrystallization behavior of various starch sources (potato, wheat, tapioca, corn, normal rice, and glutinous rice). MicroDSC results show that compared with D‐glucose (Glc), D‐fructose (Fru), and Suc, Alu does not significantly increase the gelatinization temperatures of the starch suspensions. Alu decreases water activity in the same degree as Fru in wheat, tapioca, corn, normal rice, and glutinous rice starch gels but not potato starch gels. Alu has a stronger suppression effect on recrystallization of normal and glutinous rice compared to potato, wheat, and tapioca after 14‐day storage of 2% starch pastes at 4 °C. These findings suggest that Alu can be a better plasticizer than Suc, Glc, and Fru in most starch sources but retards recrystallization of only normal and glutinous rice starches.

Impact of Starch Concentration on the Pasting and Rheological Properties of Gluten-Free Gels. Effects of Amylose Content and Thermal and Hydration Properties.

The pasting and rheological properties of starch gels from different botanical origins have been widely used to evaluate the application of these starches in pharmaceutical and food products. However, the ways in which these properties are modified by starch concentration and their dependence on amylose content and thermal and hydration properties have not been adequately established so far. An exhaustive study of the pasting and rheological properties of starch gels (maize and rice (normal and waxy in both cases), wheat, potato, and tapioca) at concentrations of 6.4, 7.8, 9.2, 10.6, and 11.9 g/100 g was performed. The results were evaluated in terms of a potential equation fit between each parameter and each gel concentration. The parameters determined for the gels at the studied concentrations were correlated with the hydration properties and thermal properties by applying principal component analysis (PCA). Wheat starch, followed by normal maize and normal rice starches, presented a greater capacity to modulate their gels' pasting and viscoelastic properties via their concentration in water. On the contrary, the characteristics of waxy rice and maize, potato, and tapioca starches were barely modified by concentration in pasting assays, but the gels of potato and tapioca showed noticeable changes in their viscoelastic properties as functions of concentration. In the PCA plot, the non-waxy cereal samples (wheat, normal maize, and normal rice) were located close to each other. Wheat starch gels were the most dispersed on the graph, which is consistent with the high dependence on the concentration of the gel shown in most of the studied parameters. The waxy starches had close positions not too distant from those of the tapioca and potato samples and with little influence from amylose concentration. The potato and tapioca samples were close to the vectors of the crossover point in rheology and peak viscosity in their pasting properties. The knowledge gained from this work allows a better understanding of the effects of starch concentration on food formulations.

In vitro fecal fermentation characteristics of mutant rice starch depend more on amylose content than crystalline structure

To obtain the relation between rice starch features and fermentation characteristics, rice starches with various polymorphic types and apparent amylose contents were subjected to in vitro fecal fermentation. Gas and short-chain fatty acid production was evaluated as a function of fermentation time, and the microbial responses were monitored by 16S rRNA sequencing technique at the end of fermentation. Regardless of polymorphic type, three high-amylose mutant rice starches (i.e., GM03, A-type; BP577, B-type; Wx21TT, C-type) displayed significantly slower fermentation rate during the first 12 h and higher final butyrate yield (17.6–17.9 mM) compared to the A-type normal starches (9311 and Wx22TT), and promoted the proliferation of Roseburia. However, A-type normal rice starches presented higher propionate production, and increased the growth of Bacteroides and Megamonas. The principal component and redundancy analyses indicated that three high-amylose mutant rice starches showed similar abundance and migration of microbial communities, and the apparent amylose content was closely correlated with the abundance of their five key amplicon sequence variants. Our results demonstrated that amylose content might be a controlling factor in determining the fermentation properties of rice starches than crystalline structure.

Pasting and Rheological Properties of Starch Paste/Gels in a Sugar-Acid System.

This study was to investigate the impact of granule size, amylose content, and starch molecular characteristics on pasting and rheological properties of starch paste/gels in neutral (water) and sugar-acid systems. Normal rice starch (RS), waxy rice starch (WRS), normal tapioca starch (TS), and waxy tapioca starch (WTS) representing small-granule starches and intermediate-granule starches respectively, were used in the study. Impacts of granule size, AM content, and their synergistic effects resulted in different starch susceptibility to acid hydrolysis and interactions between starch and sucrose-water, yielding different paste viscosities in both systems. The high molecular weight (Mw¯) and linearity of amylopectin and amylose molecules increased the consistency of starch pastes. RS produced a stronger and more brittle gel than other starch gels in both neutral and sugar-acid systems. The results indicated the impact of the effect of granule size and amylose content on starch gel behaviors. Properties of waxy starch gels were mainly governed by amylopectin molecular characteristics, especially in the sugar-acid system. Adding sugar and acid had minor impacts on starch gel behaviors in the linear viscoelastic (LVE) region but were most evident in the nonlinear response regime of starch gels as shown in the Lissajous curves at large oscillatory strain.

Insights into rice starch degradation by maltogenic α–amylase: Effect of starch structure on its rheological properties

The quality characteristics of rice-based products depend on the properties of their starch component. Maltogenic α-amylase (MA) is extensively used as an anti-staling agent in bakery foods. To expand its application in rice-based products, in the current study, normal rice starch (NRS) was subjected to MA. The enzyme susceptibility of NRS and the impact of starch fine structure changes on its rheological properties was investigated. The results reveal that NRS was less susceptible to MA, and exhibited two hydrolysis phases. As the degree of hydrolysis (DH) increased, the molecular weight of NRS decreased from 3.3 × 107 to 3.4 × 104 g/mol, while the short-chain levels (DP < 13) rose from 44.4% to 88.4%. Furthermore, compared with the control, MA treatment lowered the storage and loss moduli, and the creep properties of NRS, indicating a large attenuation in the rigidity of gel structure. The hydrolyzate pastes exhibited weaker shear thinning behavior and less hysteresis loop areas. Possible models were proposed to illustrate the crucial role of rice starch fine structures in the formation of the gel network after MA hydrolysis. These findings provide insights for exploring novel applications of the MA in rice-based products.

Characterization of storage modulus of starch suspensions during the initial stages of pasting using Stokesian dynamics simulations

This study performs Stokesian dynamics simulations of suspensions of rigid spheres to determine the conditions under which swollen starch granules can be considered rigid for rheology measurements. The first part of the study benchmarks the numerical simulations to experimental measurements of storage modulus (G′) for monodisperse polystyrene suspensions. The second part of the study compares the simulations to experimental measurements of G′ for waxy maize and normal rice starch suspensions swollen to volume fractions 0.4 < φ < 0.6. These starch granules were fractionated before swelling to create a narrow range of swollen granule sizes. For granules with a narrow size distribution, the Stokesian dynamics simulations quantitatively match the experimental G′ for volume fractions φ ≤ 0.5, but deviate significantly when φ > 0.5. These results indicate that granule deformability plays an important role when φ > 0.5, and indicates the range where one can apply theories of rigid suspension rheology.

The effects of molecular fine structure on rice starch granule gelatinization dynamics as investigated by in situ small-angle X-ray scattering

Dynamic changes of rice starch granules selected for different amylose contents were analyzed in excess water while heated in-situ in a small-angle X-ray scattering (SAXS) instrument. Normal rice starch (NS) and rice starch with high amylopectin (HAP) and high amylose (HAM) were used as models. A 1D linear correlation function and a combination power-law and Gaussian function were used to extract the starch lamellar structure parameters and the fractal dimension, ordering and distribution of starch lamellae from SAXS data. For the resulting starch paste/gels, a model of two-correlation length was fitted to afford the correlation length (ξ) for the paste/gel system. The results showed that HAM exhibited higher long period (LP) and thickness of the crystalline layers (dc) values than HAP and NS. However, HAP showed the highest ordering lamellar structure. HAP granules were more thermostable than the amylose containing starches. For the gelatinized starches, HAM showed the highest correlation length values but these notably decreased with increasing temperature indicating strong chain segment interaction. This research reveals essential structural changes in lamellae of rice starch granules and rice starch gel structure, which provides potentially useful in the working of starch-based foods and materials.

Investigating the potential of slow-retrograding starches to reduce staling in soft savory bread and sweet cake model systems

The potential anti-staling property of starches with slow-retrograding amylopectin was studied in soft wheat bread and cake model systems. Normal rice, waxy rice, and wheat starches were processed by drum drying or extrusion, and native starch was used as a comparator. Extrusion processing causing amylopectin fragmentation can reduce intermolecular retrogradation of rice starch. Starches were incorporated into model breads and cakes as partial replacements for flour on a dry weight basis (3 and 6% for cakes, 5 and 15% for breads). Starches pregelatinized by extrusion had moderate molecular fragmentation, as indicated by RVA and HPSEC-MALLS-RI. Starches previously shown to have lower intermolecular retrograding amylopectin (normal rice, waxy rice) resulted in minor to moderate reductions in hardness and other textural properties as indicated by texture profile analysis (TPA) in breads and cakes upon storage for up to 12 wk. A higher degree of starch fragmentation is suggested to produce lower staling. Incorporation of normal and waxy rice starches resulted in softer breads and cakes than wheat starch, which could be attributed to the shorter external and internal amylopectin chains of rice starch. Higher inclusion (15%) of slow-retrograding waxy rice in the bread model system showed the most potential for anti-staling property.

The effect of pH on the chemical and structural interactions between apple polyphenol and starch derived from rice and maize.

To date, how pH affects starch–polyphenol mixtures has not been thoroughly investigated. This study explored the impact of combining apple polyphenol (AP) with both normal rice starch (NRS) and normal maize starch (NMS) across a range of pH conditions. NRS–AP mixture particle sizes across a pH range of 3–8 varied from 169.9 ± 5.4 to 187.5 ± 6.9 μm, while for NMS–AP particles, these sizes ranged from 161.8 ± 8.0 to 176.0 ± 4.9 μm, indicating that the aggregation of starch–AP was inhibited under low pH condition. The melting enthalpy (△H) values of the NRS–AP mixture across a pH range of 3–8 were 8.50 ± 0.06–9.56 ± 0.12 J/g, while the corresponding value for the NMS–AP mixture was 5.77 ± 0.05–6.21 ± 0.08 J/g. FTIR analyses revealed that the degree of order of these starch–AP mixtures significantly decreased under low pH conditions. XRD analysis further revealed that both NRS–AP and NMS–AP mixtures exhibited V‐type structures, and relative crystallinity levels decreased significantly under low pH conditions. Together, these results indicate that low pH values inhibit the recrystallization of NRS–AP and NMS–AP mixtures. Overall, these findings provide additional evidence regarding the interactions between AP and specific starches under a range of pH conditions.

Enzymatically elongated rice starches by amylosucrase from Deinococcus geothermalis lead to slow down the glucose generation rate at the mammalian α-glucosidase level

Amylosucrase (AS) catalyzes the transfer of a glucosyl unit from sucrose onto α-1,4-linked glucan polymers in starch. In this study, AS from Deinococcus geothermalis (DgAS) was applied to produce modified rice starches with slowly digestible properties. DgAS-treated waxy and normal rice starches showed significantly (p < 0.05) elevated degrees of polymerization, suggesting that the external chains were elongated. Additionally, the crystalline structures of starches changed from A- to B-type, and the temperature transition properties of enzymatically modified rice starches increased. The amounts of slowly digestible starch (SDS) increased remarkably (20.1% and 18.8%; waxy and normal rice starches, respectively), and the DgAS-treated rice starches were slowly hydrolyzed to glucose at the mammalian mucosal α-glucosidase level. Thus, DgAS-treated rice starches can be used to produce SDS-based ingredients that attenuate the glucose spike after glycemic food ingestion.

Improving resistance of crystallized starch by narrowing molecular weight distribution

Crystallized debranched waxy rice starch had higher resistant starch (RS) content and crystallinity than crystallized debranched normal rice starch. Thus, debranched waxy rice starch (Unf) with molecular-weight dispersity (DM) at 2.161 was fractionated into F1, F2 and F3 with the DM at 1.604, 1.466 and 1.658, respectively. Moreover, the peak molecular weight of Unf, F1, F2 and F3 was 3.146e + 03, 2.906e + 03, 3.585e + 03, and 4.178e + 03 Da, respectively. Obviously, Unf had higher molecular weight but wider distribution than F1. After crystallization, Unf and F1 had similar RS content and crystallinity. Similar phenomenon occurred to F2 and F3. These results suggested that narrowing molecular weight distribution promoted crystallization of starch and improved its resistance. To further improve efficiency of preparing RS by crystallization, crystallization of F3 was optimized. Under the optimal conditions, the yield and RS content of crystallized F3 reached 81.2% and 80.6%, respectively.

Swelling kinetics of rice and potato starch suspensions

AbstractGranule size distribution of 8% w/w suspension of normal rice starch (NRS), waxy rice starch (WRS), modified potato starch (MPS), and normal potato starch (NPS) in water when subjected to heating at 60, 65, 70, 75, 80, and 85°C at different hold times (0–60 min) were characterized. The average starch granule diameter was larger at higher temperatures and hold times for NRS, WRS, and MPS indicating swelling, whereas for NPS it decreased indicating breakage. Swelling varied in the order: MPS &gt; NRS &gt; WRS. Earlier proposed pseudo first‐ and second‐order kinetic and Weibull models for swelling were evaluated. Swelling kinetics was also predicted using our previously developed mechanistic model (Desam et. al., 2018a Journal of Food Engineering 222:237–249) whose predictions agreed well with the experimental data of mean granule diameter and granule size distribution with time at different temperatures, and therefore can be employed to describe swelling at different processing conditions.Practical ApplicationsStarches are incorporated in food products for a variety of reasons such as stabilizing, thickening, binding, and gelling. Starch occurs as discrete granules. Upon exposure to water, starch granules swell when heated. This results in thickening of starch suspension (known as pasting) due to an increase in volume fraction of swollen granules. Starch pasting results in an increase in its viscosity. Therefore, the texture of a variety of food products such as sauces, puddings, soups, batter mixes, and so forth are influenced by pasting. The rheology and texture of starch paste obtained by cooking of starch granules are governed by its swelling. It is, therefore, necessary to quantify swelling in order to predict the rheology of starch paste as well as to develop new food formulations. We developed a mechanistic model which predicts the swelling kinetics of rice and potato starch suspensions.

Effects of high pressure homogenization on rheological properties of rice starch

ABSTRACTGelatinized starch paste was prepared by gelatinizing rice starch at 95 °C in a water bath. Then, the rice starch (both normal rice starch and waxy rice starch) paste was subjected to high-pressure homogenization at homogenizing pressure of 20, 40, 60, 80 MPa. The rheological properties (including shear stress versus shear rate, apparent viscosity versus shear rate and thixotropy) of starch paste were studied. The high-pressure homogenization was able to improve the flow properties of starch paste. The shear stress increased with the increasing shear rate, and the Power law equation was capable of fitting the shear stress versus shear rate quite precisely. High-pressure homogenization treatment sharply decreased the thixotropy of starch paste, and the thixotropy of rice starch (both NRS and WRS) paste decreased with the increasing homogenous pressure.

Effects of pandan aqueous extract on physico-chemical properties of normal and waxy rice starches

Pandan aqueous extract (PAE) has traditionally been used as a food additive in Southeast Asia to enhance their flavor, color and health benefits. The purpose of this research was to investigate the effects of PAE on physico-chemical properties of normal rice starch (NRS) and waxy rice starch (WRS). Results indicate that addition of PAE significantly (p &lt; 0.05) affected the physico-chemical properties of rice starches. For pasting properties, PAE significantly increased peak viscosity, breakdown and pasting temperature of NRS, while PAE decreased peak viscosity, breakdown, final viscosity and setback values of WRS. The addition of PAE to NRS and WRS significantly (p &lt; 0.05) reduced gel hardness and gel adhesiveness by more than 50% compare to native control gels. The gelatinization thermal properties of both NRS and WRS were significantly (p &lt; 0.05) increased when PAE was included. Only the gelatinization enthalpy of WRS was influence by the PAE. It was concluded that the addition of PAE considerably improved the thermal stability of WRS.

Role of entanglement concentration in dynamic viscoelasticity and film-forming property of cereal starches

Entanglement concentration (ce, w/v) means the onset of overlap and interpenetration of random-coil chains in a macromolecule solution. The effects of ce on the dynamic viscoelasticity and film-forming property of cereal starches were investigated. The results showed that ce affected significantly the ratio of crystalline to amorphous regions of normal rice starch, waxy rice starch, normal maize starch and wheat starch because the absorbance ratio (1047cm−1/1022cm−1) increased more obviously at concentrations increasing from 0.1% to ce. Storage modulus increased faster than loss modulus with increasing frequency. The presence of lower entanglement density and stronger mobility of the chain segments in normal rice starch due to the highest crossover, whereas the contrary is the case for waxy rice starch. But, no crossover point occurred in four cereal starch dispersions at concentrations <ce. The normal maize and wheat starch dispersions at concentrations around ce showed a Newtonian behaviour at low angular frequency, whereas it exhibited a shear-thinning behaviour at higher frequency. The normal rice and waxy rice starch dispersions exhibited a shear-thinning behaviour throughout the entire frequency. Four cereal starch films could only develop at concentrations ≥ce. Comparatively, wheat and normal rice starches had good filming properties.

Evaluation of the Molecular Structural Parameters of Normal Rice Starch and Their Relationships with Its Thermal and Digestion Properties.

The molecular structural parameters of six normal rice starches with different amylose contents were investigated through their iodine absorption spectra and gel permeation chromatography of fully branched and debranched starches. The thermal and digestion properties of starches were also determined and their relationships with molecular structural parameters were analyzed. Results showed that the molecular structural parameters of maximum absorption wavelength, blue value (BV), optical density 620 nm/550 nm (OD 620/550), amylose, intermediate component, and amylopectin, including its short branch-chains, long branch-chains, and branching degree, had high correlation in different determining methods. The intermediate component of starch was significantly positively related to amylose and negatively related to amylopectin, and the amylopectin branching degree was significantly positively related to amylopectin content and negatively related to amylose content. The gelatinization temperatures and enthalpy of native starch were significantly positively related to BV, OD 620/550, and amylose content and negatively related to amylopectin short branch-chains. The gelatinization temperatures and enthalpy of retrograded starch were significantly negatively related to amylopectin branching degree. The digestions of gelatinized and retrograded starches were significantly negatively related to the BV, OD 620/550, amylose, and intermediate component and positively related to amylopectin and its short branch-chains and branching degree.

Small-granule starches from sweet corn and cow cockle: Physical properties and amylopectin branching pattern

Small-granule starches (SGS) attract growing interests with their unique structure and functionalities, such as fat replacement and texture modifications. To explore new resources of SGS, sweet corn starch (SCS) and cow cockle starch (CCS) were studied for their physical properties and branching pattern, with normal corn starch, waxy corn starch, normal rice starch, and waxy rice starch as comparisons. Hydrothermal and wide-angle X-ray powder diffraction analyses showed the much lower content of ordered structure (melting enthalpy of 5.6 J/g) and lower crystallinity (28%) for SCS than for normal corn starch (14.4 J/g and 34%, respectively). The rapid viscosity analyzer analysis showed very low viscosity for SCS through the pasting process and high resistance of CCS against the shear force. The results of β-limit dextrin structure analyses showed highly branched clusters of SCS (about 15 glucan chains per cluster) and a lack of long inter-cluster chains that connect 3 or more clusters. In contrast, CCS displayed a branching pattern similar to that of corn starches, however, with fewer short intra-cluster chains. It was considered that the low crystallinity and viscosity of SCS were attributed to its high branching, which reduced the formation of crystalline structure during the genesis of starch and decreased the interactions among swollen granules. On the other hand, the submicron size made CCS granules less susceptible to the shear force applied during pasting, leading to negligible breakdown. Using SCS and CCS as models, this study connected the physical properties and branching pattern of SGS, thus supporting their potential applications.

Complexation of rice starch/flour and maize oil through heat moisture treatment: Structural, in vitro digestion and physicochemical properties

This study investigated structural, in vitro digestion and physicochemical properties of normal rice starch (NRS)/flour (NRF) complexed with maize oil (MO) through heat-moisture treatment (HMT). The NRS-/NRF-MO complex displayed an increased pasting temperature and a decreased peak viscosity. After HMT, less ordered Maltese and more granule fragments were observed for NRS-/NRF-MO complex. Meanwhile, more aggregation was observed in the HMT samples with higher moisture contents. We found that higher onset temperature, lower enthalpy change and relative crystallinity of the NRS-/NRF-MO complex were associated with a higher moisture content of HMT samples. The higher moisture content of HMT was also favorable for the amylose-lipid complex formation. Differences in starch digestion properties were found for NRS-MO and NRF-MO complex. All of the NRS/NRF complexed MO after cooking showed lower rapidly digestible starch (RDS) contents compared with the control sample, therein NRS-/NRF- MO 20% exhibited the highest sum of the slowly digestible starch and resistant starch contents. In general, HMT had a greater impact on the in vitro digestion and physicochemical properties of flour samples compared with starch counterparts.

Production of an in Vitro Low-Digestible Starch via Hydrothermal Treatment of Amylosucrase-Modified Normal and Waxy Rice Starches and Its Structural Properties.

We investigated dual modification of normal and waxy rice starch, focusing on digestibility. Amylosucrase (AS) was applied to maximize the slowly digestible and resistant starch fractions. AS-modified starches were adjusted to 25-40% moisture levels and heated at 100 °C for 40 min. AS-modified starches exhibited a B-type crystalline structure, and hydrothermal treatment (HTT) significantly (p < 0.05) increased the relative crystallinity with moisture level. The thermal transition properties of modified starches were also affected by the moisture level. The contents of rapidly digestible starch fraction in AS-modified normal and waxy starches (43.3 ± 3.9 and 18.1 ± 0.6%) decreased to 13.0 ± 1.0 and 0.3 ± 0.3% after HTT, accordingly increasing the low digestible fractions. Although the strengthened crystalline structures of AS-modified starches by HTT were not stable enough to maintain their rigidity under cooking, application of AS and HTT was more effective in waxy rice starch than normal rice starch when lowering digestibility.