Amylose Chains Research Articles

Comparison of the structure and properties of hydroxypropylated acid-hydrolysed maize starches with different amylose/amylopectin contents

Dually modified regular maize starch (RMS) and high-amylose maize starch (HAMS) were successfully prepared by first acid hydrolysis and subsequently hydroxypropylation. The effects of hydrolysis time (0–24 h) and propylene oxide (PO) content (10–30%) on the structure and physicochemical properties were investigated. The molar substitution (MS) of HAMS samples (up to 0.163) was generally higher than that of RMS samples (up to 0.149), suggesting the higher reactivity of amylose for hydroxypropylation. Besides, PO content had a greater influence on MS whereas the effect of acid hydrolysis time was minor. For both starches, the dual modifications did not cause apparent changes to the granule morphology but reduced gelatinisation temperatures and enthalpy; and a higher PO content led to higher relative crystallinity. These results suggest that hydroxypropylation occurred mainly on the surface of HAMS granules and had little influence on the compact granular structure, whereas this reaction impacted the internal structure of RMS much more. The rheological study shows the introduced hydroxypropyl bulky groups weakened the entanglements between amylose chains or amylopectin chains with long branches. Thus, this work provides insights into the rational design of modified starch products containing different amylose/amylopectin contents with tailored properties.

The relationship between the expression pattern of starch biosynthesis enzymes and molecular structure of high amylose maize starch

Two high amylose (HAM) inbred lines with apparent amylose contents of 55 % and 62 %, respectively, were selected to explore the relationship between molecular structure and gene expression of starch-synthase involved enzymes. GPC analysis of debranched starches showed that the HAM starches (HAMSs) had shorter amylose chains and longer amylopectin chains than normal maize starch (NMS). FACE analysis showed that these HAMSs had a higher content of amylopectin chains of DP > 21. Quantitative Real-Time PCR analysis showed that the HAM lines had specifically low expression of the starch branching enzyme IIb (SBEIIb), and the starch synthase IIIa (SSIIIa) homologue, and high expression of the isoamylase 2 (ISA2), potentially suppressing the generation of amylopectin molecules through deficient branching and excessive debranching process, thereby increasing the relative amylose content. A high expression of GBSS1 was potentially associated with increased short amylose chain lengths in HAMSs.

Conformation of Pullulan in Aqueous Solution Studied by Small-Angle X-Ray Scattering.

Small-angle X-ray scattering functions were measured for six pullulan samples with molecular weights ranging from 2.3 × 104 to 7.4 × 105 in 0.05 M aqueous NaCl at 25 °C and fitted by the perturbed wormlike chain model, comprising touched-bead sub-bodies, to obtain wormlike chain parameters. The parameter values determined were consistent with those determined from previously reported dilute solution properties of aqueous pullulan. Because radii of gyration of not only pullulan polymers, but also pullulan oligomers were consistently explained by the touched-bead wormlike chain model perturbed by the excluded volume effect, the pullulan chain takes a local conformation considerably different from the amylose chain, although both polysaccharides are flexible polymers with an approximately same characteristic ratio.

Effect of dual chemical modification on the properties of biodegradable films from achira starch

AbstractThe objective of this study was to evaluate the effect of a dual modification (acid hydrolysis and succination) on the structural, mechanical, thermomechanical, and permeability properties of films from achira starch. Micrographs of films revealed a smooth surface and some remnants of starch granules, indicating a partial gelatinization. Tensile strength and percentage of elongation increased in films from double modified starch (10.50 MPa and 42.83%, respectively). The OH groups formed in the amylose and amylopectin chains during the hydrolysis and the alkoxide groups (RO−) generated during the succination resulted in high values of water vapor permeability (3.215 × 10−10 g/s m Pa). The glass transition temperature (Tg) of films from hydrolyzed–succinated starch was decreased due to the reduction of the molecular weight of the polymeric chains and the presence of succinate groups that reduced the molecular interactions of the polymeric chains, increasing the mobility and therefore decreasing the softening temperature.

A molecular explanation of wheat starch physicochemical properties related to noodle eating quality

The relationship between wheat-starch molecular structures (obtained by size-exclusion chromatography), physicochemical properties (swelling power (SP), pasting and thermal properties) and noodle eating qualities were examined. SP was negatively correlated with amylose content and positively correlated with the amounts of amylose long chains and short amylopectin chains. Peak viscosity (PV) was negatively correlated with amylose content and the amount of long amylopectin chains, but positively correlated with the lengths of long amylopectin chains and the amount of short amylopectin chains. Noodles adhesiveness was negatively correlated with the amount of short amylose chains, short amylopectin chains, PV and final viscosity (FV). Noodles hardness was positively correlated with amylose content and long amylopectin chains, but negatively correlated with short amylopectin chains, SP, PV, and FV. All these observations are explained in terms of molecular mechanisms. This provides the first associations between starch molecular fine structures (instead of only amylose content) responsible for starch properties of importance in making noodles.

Amylose content and specific fine structures affect lamellar structure and digestibility of maize starches

The molecular and lamellar structures and in vitro digestibility of high amylose maize starch granules were investigated. Size-exclusion chromatography (SEC) analysis of hydrodynamic radius (Rh) and relative contents (RC) of different amylose and amylopectin pools revealed that increased amylose content resulted in the decrease of RC of short amylopectin chains (AP1, DP < 36), and the increase of Rh and RC of long amylopectin chains (AP2, DP > 36). Fluorophore-assisted carbohydrate electrophoresis (FACE) analysis showed the average chain lengths of defined structures of fa, fb1, and fb3, and the content of fb3 were increased with the amylose content and at AC content of 43%, the chain lengths decreased with the amylose content. The relative contents of fa and fb1and the degree of branching had the converse trends. Hence, HA-2, having an AC content of 43%, was the tipping point for these structural changes. Small angle X-ray scattering (SAXS) and its normalized 1D correlation function and SAXS scattering curve parametric fitting showed that the crystalline lamellar thickness was negatively correlated with proportion of short amylose chains (AM1, 100 <DP ≤ 150). The Bragg lamellar repeat distance was positively correlated to Rh of the intermediate amylose chains (AM2, 150< DP ≤ 800). The amorphous lamellae thickness was positively correlated with the Rh of long amylose chains (AM3, 800 <DP ≤ 40,000). The positive correlation between Rh of AM2 on the Gaussian peak area and the scattering invariant suggests AM2 chains stabilize the lamellar structure. Both the digestion rate of the digestible starch as well as the resistant starch content were positively correlated with amylose content. Pearson correlation analysis demonstrated that longer amylopectin chains and lower content of AP1 chains were positively correlated with the digestion rate.

The contribution of β-glucan and starch fine structure to texture of oat-fortified wheat noodles

Wheat flour noodles are sometimes fortified with β-glucan for nutritional value, but this can decrease eating quality. The contributions of β-glucan and starch molecular fine structure to physicochemical properties of wholemeal oat flour and to the texture of oat-fortified white salted noodles were investigated here. Hardness of oat-fortified noodles was controlled by the longer amylopectin chains (DP ≥ 26) and amount of longer amylose chains (DP ≥ 1000). Higher levels of β-glucan, in the range from 3.1 to 5.2%, result in increased noodle hardness. Pasting viscosities of wholemeal oat flour positively correlate with the hardness of oat-fortified noodles. The swelling power of oat flour is not correlated with either pasting viscosities of oat flour or noodle hardness. Longer amylopectin chains and the amount of longer amylose chains both control the pasting viscosities of oat flour, which in turn affect noodle texture. This provides new means, based on starch and β-glucan molecular structure, to choose oats with optimal starch structure and β-glucan content for targeted oat-fortified noodle quality.

Effects of pullulanase pretreatment on the structural properties and digestibility of lotus seed starch-glycerin monostearin complexes

The effects of pullulanase pretreatment, combined with ultrasound-microwave synergistic processing, on the structural properties and digestibility of lotus seed starch-glycerin monostearin complexes was investigated. The pullulanase pretreatment improved the complex index of the inclusion complexes. The structural properties analysis indicated the debranching of starch by pullulanase facilitated an increase in microcrystalline regions and ordering of starch. However, extensive debranching resulted in a blend of B- and V-type crystalline structures and a high degree of freedom of amylose chains. The microstructural morphology revealed that pullulanase debranching inhibited the gelatinization of starch by promotion of V-complex formation, while excessive enzymolysis did not. The stability of starch complex structure determined its digestibility, and the digestion analysis revealed that 100 min of pullulanase debranching contributed to the high content of V-type resistant starch. After that, starch helix conformations was more inclined to imperfect amylose double helices, reflecting an increase in slowly digestible starch content.

Effect of Natural Fermentation of Sorghum on Resistant Starch Molecular Structure and Fermentation Property

Relevant research results have suggested that fermentation can increase the content of sorghum amylose chains and their retrogradation value. Therefore, this study explored the effect of fermentation pretreatment on the yield, digestibility, molecular structure, and in vitro fermentation property of sorghum-resistant starch by conducting fermentation pretreatment of sorghum and extracting the resistant starch from fermented sorghum with pressure-heat compound enzyme method. The results were as follows. After fermentation pretreatment, the yield of sorghum-resistant starch increased, the digestibility of sorghum-resistant starch reduced, the laminated structure size on the surface of the particles became more uniform, and the stacking mode became more neat and denser. The sorghum-resistant starch prepared before and after fermentation did not produce new chemical groups, and its functional group peak remained unchanged. After fermentation, the weight-average molecular weight of sorghum-resistant starch was elevated, and the percentage content of high- and low-molecular substances increased and decreased, respectively, compared with that of the unfermented sorghum-resistant starch. The percentage content of short-chain branches in the branched chain increased, whereas that of the long-chain branches decreased; the crystallinity of sorghum-resistant starch after fermentation decreased, and the intensity of X-diffraction peak changed slightly before and after fermentation. According to the results of the in vitro fermentation experiments, the fermentation broth of sorghum-resistant starch had the highest content of butyric acid and short-chain fatty acid. Research results reveal that, after fermentation pretreatment, sorghum-resistant starch presented increased yield, more complex molecular structure, heavier molecular weight and more uniform surface morphology, more efficient butyric acid generation, and greater fermentation rate than unfermented sorghum-resistant starch.

Preparation of VII-type normal cornstarch-lauric acid complexes with high yield and stability using a combination treatment of debranching and different complexation temperatures

To improve the yield and stability of VII-type cornstarch-lauric acid complexes and inhibit the digestibility of starch, debranched cornstarch was used to complex with lauric acid under a low complexation temperature and a high complexation temperature (DSL30 and DSL90). Debranching treatment raised the yield of the complexes and the melting enthalpy, which reached 51.4% and 14.26 J/g for the complex DSL90, respectively. Complexes formed at high complexation temperature showed high melting temperature ranged in 102.71 °C–120.30 °C, indicating high thermal stability. As the complexation temperature increased from 30 °C to 90 °C, the complexes transformed from VI-type to VII-type. The combination of debranching treatment and increasing complexation temperature decreased the in vitro digestibility of the complexes. The highest resistant starch content was found in the complex DSL90, which also exhibited a lamellar structure under the scanning electron microscopy. The root mean square deviation under the molecular dynamics simulations of the complexes was lower than that of single amylose, suggesting that the complexation with lauric acid could keep the conformation of the amylose chain stable. Debranching treatment combined with a high complexation temperature may be used as an applicable method to prepare VII-type starch-fatty acid complexes with high stability.

Effects of Nonstarch Genetic Modifications on Starch Structure and Properties.

This paper examines if, in maize, starch structure and starch-dependent properties might be altered by pleiotropic effects arising from genetic modifications that are not directly related to starch synthesis. The molecular structure, specifically the starch chain-length distributions (CLDs), of two maize lines transformed with Bar (bialaphos resistance) and Cry1c genes (an artificial gene, encoding proteinaceous insecticidal δ-endotoxins) were compared to those of their control lines. The two transgenes are responsible for herbicidal resistance and insect tolerance, respectively. The starch CLDs were measured by enzymatic debranching and measuring the molecular weight distributions of the resulting linear chains. It was found that although all the lines had similar amylose contents, the CLDs of both amylopectin and amylose for Cry1c were noticeably different from the others, having more short amylopectin and long amylose chains. These CLDs are known to affect functional properties, and indeed it was found that the Cry1c transgenic lines showed a lower gelatinization temperature and faster digestion rate than the control or Bar lines. However, a slower digestion rate is nutritionally desirable. Thus, pleiotropic effects from genetic modifications can indirectly but significantly affect the starch synthesis pathway and thus change functional properties of significance for human health.

Synthesis of Amylosic Supramolecular Materials by Glucan Phosphorylase-Catalyzed Enzymatic Polymerization According to the Vine-Twining Approach

This article overviews the synthesis of amylosic supramolecular materials through inclusion complexation in glucan phosphorylase (GP)-catalyzed enzymatic polymerization. Amylose is a polysaccharide that is known to form inclusion complexes with a number of hydrophobic small guest molecules. A pure amylose can be synthesized by the enzymatic polymerization of α-d-glucose 1-phosphate monomer with a maltooligosaccharide primer catalyzed by GP. The author has reported that the propagating amylosic chain in the enzymatic polymerization twines around hydrophobic polymers present in aqueous reaction media to form supramolecular inclusion complexes. As it is similar to the way that vines of a plant grow around a rod, this polymerization is termed ‘vine-twining polymerization’. Amylosic supramolecular network materials have been obtained through the vine-twining polymerization by using copolymers, where hydrophobic guest polymers are covalently grafted on hydrophilic main-chain polymers. The enzymatically produced amylosic chains form complexes with the guest polymers among graft copolymers, which act as cross-linking points to form supramolecular networks, resulting in the formation of soft materials, such as gels and films. Vine-twining polymerization using appropriately designed guest polymers has also been performed, which leads to supramolecular products that exhibit new functionality.1 Introduction2 Vine-Twining Polymerization to Form Supramolecular Inclusion Complexes3 Selective Complexation of Amylose toward Guest Polymers in Vine-Twining Polymerization4 Hierarchical Architecture of Amylosic Supramolecular Network Materials by Vine-Twining Polymerization Approach5 Hierarchical Fabrication of Amylosic Supramolecular Materials by Vine-Twining Polymerization Using Designed Guest Polymers6 Conclusions

Changes in the physicochemical properties and starch structures of rice grains upon pre-harvest sprouting

In rice production, pre-harvest sprouting (PHS) of late ripening seeds is one of the most serious quality defects in rice grain quality. In the present study, PHS impact was investigated by examining the physicochemical properties, eating and cooking quality (ECQ) of rice grain. Four rice cultivars suffering from PHS had impaired ECQ, reduced apparent amylose content, and decreased total starch content, with an increase in total protein content. The viscosity of flours and starches prepared from the PHS grains was significantly reduced. Starch molecular structure analysis also showed remarkable decreases in the short chains of amylopectin, long amylose chains and reduced starch crystallinity of the PHS grains. Moreover, the PHS native starch tended to have low starch digestibility. This provides useful information for understanding the effects of PHS on white rice grain quality as well as on starch fine structure and its physicochemical properties.

Amylolysis as a tool to control amylose chain length and to tailor gel formation during potato-based crisp making

Potato flakes (PFs) are used for producing potato-based crisps. Their cold-water swelling starch instantly binds water during dough mixing. The dough is then sheeted and deep-fried. We here used α-amylase from Bacillus subtilis (BSuA) and Bacillus stearothermophilus (BStA) to unravel the role of PF amylose (AM) during crisp production. Treating PFs with BSuA [30.0 EU/g PF dry matter (dm), 10 min, 40 °C] increased the extractable starch (E-S) content from 8.6 to 42.7% of PF dm but the degree of polymerization (DP) of the E-S chains was lower than 150. Although time domain proton nuclear magnetic resonance (TD 1H NMR) analysis showed that these enzymatically released starch chains with DP lower than 150 readily crystallize during dough making, they are not able to contribute to formation of strong gels. In contrast, amylolysis of PF starch by BStA (30.0 EU/g PF dm, 10 min, 40 °C) only slightly impacted the E-S content (11.0% of PF dm) but increased the level of relatively short extractable amylose (E-AM) chains [(DP between 150 and 1500 (E-AM150-1500)] by 35%. Incubation (10 min, 60 °C) of 7.8% of the PF dm in the dough recipe with the same BStA dosage prior to dough making showed that E-AM150-1500 chains increase the extent of AM crystallization during dough making (as evidenced by TD 1H NMR analysis) and thereby strengthen the starchy gel network. As a consequence, expansion of the food matrix during deep-frying was hampered, which increased product hardness and reduced oil uptake by 10% and 8%, respectively. This study is the first to show that the level of AM chains of intermediate length is crucial for the texture of potato-based food matrices.

Study on the mechanism of ultrasound-accelerated enzymatic hydrolysis of starch: Analysis of ultrasound effect on different objects

Enzymatic hydrolysis of starch is an important process in the food industry. In the present work, ultrasound was introduced in glucoamylase pretreatment, starch pretreatment and mixed reaction system treatment to enhance starch hydrolysis efficiency. These different processes were studied to explore the mechanism of ultrasound in promoting enzymatic reactions. The hydrolysis degree of starch was determined via measuring the reducing sugar yield. Ultrasound caused enzyme inactivation under high temperatures, high ultrasonic power and long-time treatment, especially at high temperatures exceeding 65 °C. Ultrasound pretreatment of starch before enzymolysis led to the furtherance of starch hydrolysis degree. Meanwhile, sonicating the mixed enzymatic reaction system below 65 °C promoted starch hydrolysis significantly, inducing more than five- fold growth in the degree of starch hydrolysis as much as the ultrasound pretreatment caused. Molecular weights analysis conducted by the MALLS system reflected the enormous damage of starch molecules caused by ultrasound. The amylose contents and chain length distributions of samples were separately analyzed by iodine binding method and size exclusion chromatography. The results of the two experiments illustrate that ultrasound could promote the enzymatic hydrolysis of amylopectin, which is harder for glucoamylase to hydrolyze compared to amylose.

Structural and functional characterizations of α-amylase-treated porous popcorn starch

The structures and properties of normal popcorn starch (PCS) and porous PCS were studied. In comparison with normal dent corn starch (DCS), PCS had more amylopectin chains with degree of polymerization (DP) 12–24, fewer amylopectin chains with DP > 36, and shorter amylose chains. PCS had a lower crystallinity, a more disordered lamellar structure, thicker lamellae, larger granules, a more porous granular surface, lower viscosity, and a lower gelatinization temperature than DCS. After α-amylase hydrolysis at sub-gelatinization temperatures, both PCS and DCS had more porous granular surfaces, shorter amylose and outer amylopectin chains, and higher relative crystallinities. However, as compared to DCS, PCS had a lower overall yield, larger pores, a higher percentage of hydrolyzed amylose and long amylopectin chains, smaller granules, and greater water- and oil-absorption capacities. These differences were attributed to the indentations on the granular surface of PCS as well as to its fragile structure. These results increased our understanding of the structures and properties of PCS, and provided a framework for PCS preparation. In addition, our results suggested that PCS has a high potential for porous starch applications.

Drying treatments on Chinese yam (Dioscorea spp.) prior to wet milling influence starch molecular structures and physicochemical properties

The molecular structures and physiochemical properties of starches isolated from Chinese yam (Dioscorea spp.) slices with various drying treatments (including hot air-drying at different temperatures, microwave freeze drying and ultrasonically enhanced hot air-drying) prior to wet milling were examined. The average whole molecular size (Rh¯) and debranched amylopectin chain length (X¯) were significantly decreased whereas the amylose chains and content presented negligible changes after drying. These structural modifications are consistent with the observed higher pasting viscosity, lower gelatinization temperatures and enthalpy changes, and greater digestion rate and extent for the dehydrated yam slices compared to that for the fresh yam. Among the drying techniques applied, the microwave freeze drying (MFD) resulted in the greatest amylopectin degradation with the smallest Rh¯ and X¯ along with the largest amount of short amylopectin chains (DP 6–12) due to the highly intensive moisture removal process. Correspondingly, the MFD contributed to the lowest gelatinization temperatures and enthalpy changes while the highest digestibility. The molecular degradation generally increased with increasing hot air-drying temperature, agreement with the corresponding functional changes. The structure-property correlations indicates the significant roles of starch molecular structures in controlling the drying-induced physicochemical changes. This study can be used to suggest ways in which some improved functional properties of yam starch-based products can be obtained through optimal drying techniques.

HMDSO plasma treatment as alternative to modify structural properties of granular starch

In the present study, the effect of plasma treatment on the structural properties of three granular corn starches (normal, Hylon V and Hylon VII) was investigated. Thermal (TGA/DSC), structural (XRD/FTIR) and chemical (XPS) properties were evaluated. Plasma treatment resulted in partial evaporation of water molecules changing the organization level of the double helices in the crystalline lamellae. Moreover, XRD results suggested a decrease of the long-range crystallinity and suggested changes in amylose chains after treatments. The crosslinking of modified amylose chains measured by XPS analysis resulted in variations in the gelatinization parameters as well as in its heterogeneous crystalline structure. The results indicate that the type and extent of changes in the structure of plasma-treated corn starch depends on the distribution of the water molecules inside the crystalline regions (helical water) and on the amylose content. In addition, the obtained results indicated that plasma treatment is a suitable method to modify starch without any incorporation of new elements from hexamethyldisiloxane (HMDSO), which only promotes stronger interactions between the starch main components.

New insights into amylose and amylopectin biosynthesis in rice endosperm

How various isoforms of rice-starch biosynthesis enzymes interact during amylose and amylopectin synthesis is explored. The chain-length distributions of amylopectin and amylose from 95 varieties with different environmental and genetic backgrounds were obtained using size- exclusion chromatography, and fitted with biosynthesis-derived models based on isoforms of starch synthase (SSI-SSIV), starch branching enzyme (SBE, including SBEI and SBEII) and granule-bound starch synthase (GBSS) that are involved in amylose and amylopectin synthesis. It is usually thought that these are synthesized by separate enzymes. However, the amount of longer amylopectin chains correlated with that of shorter amylose chains, indicating that GBSS, SBE and SS affect both amylose and amylopectin synthesis. Further, the activity of GBSS in amylose correlated with that of SS in amylopectin. This new understanding of which enzymes are suggested by the statistics to be involved in both amylose and amylopectin synthesis could help rice breeders develop cereals with targeted properties.

Study on crystalline, gelatinization and rheological properties of japonica rice flour as affected by starch fine structure

Although many researches have investigated the effects of starch characteristics on its functional properties to evaluate rice quality, few studies were carried out the correlations between starch molecular structure and rice processing properties. In this study, eight varieties of japonica rice with similar content of protein and lipid and less variant content of amylose (12.12–18.19%) were elaborately selected. The result showed that crystalline and pasting parameters were mainly reliant on the differences in chain length distribution of amylopectin. Amylose content and chain length distribution, especially for average exterior chain length (ECL) and interior chain length (ICL) and their entanglement, showed significant correlation on rheological parameters. Swelling power of rice flour showed negative correlation with amylose content. Furthermore, in temperature-reduction process when the temperature is lower gelatinization temperature of amylopectin, the variation of loss modulus was affected by amylopectin. In addition, the PCA plot clearly revealed the interrelationship of all parameters.