Amylopectin Starch Research Articles

Starch gelatinization using sodium silicate: FTIR, DSC, XRPD, and NMR studies

AbstractThe chemical and physical modifications of native maize starch subjected to treatment with aqueous Na silicate have been investigated. The application of FTIR, DSC, XRPD, and NMR analysis is discussed herein with respect to the interaction of Na silicate with starch in relation to gelatinization. XRPD results indicate that Na silicate, in the ionized form, disrupts the molecular structure of starch in a manner similar to thermally induced starch gelatinization. In addition, Na silicate forms new CO–O–SiO2Na moieties with the amylopectin starch component. This was ascertained by the detection of the in‐plane vibration of the –Si–O as a distinctive FTIR band at 580–600 cm−1 and the appearance of a new carboxyl group (–COOH) NMR chemical shift at 168 ppm for the amylopectin/Na silicate system. DSC analysis showed two adjacent endothermic transitions at 192 and 198°C for starch/amylopectin treated with Na silicate whereas amylose treated with Na silicate did not show any new endothermic/or exothermic transitions.

Amylose and amylopectin in starch by asymmetric flow field-flow fractionation with multi-angle light scattering and refractive index detection (AF4–MALS–RI)

The rheological and functional properties of starch are influenced by the size and molar mass distribution of the polymer, the ratio of amylose (AMY) to amylopectin (AMP), and branching characteristics. Asymmetric Flow Field-Flow Fractionation (AF4) was applied to fractionate five different maize hybrids of varying AMY:AMP ratio. When coupled to detection by multi-angle light scattering and refractive index (MALS–RI), it was possible to determine mass percentage and the average weight-average molar mass (Mw) without the need for calibration standards. Sufficient resolution of amylose and amylopectin was achieved by applying a gradient cross-flow on a 17 cm trapezoidal channel with a 350 μm spacer. The observed Mw ranged from about 2 × 105 to 4 × 105 for amylose and from 1 × 108 to 4 × 108 for amylopectin. The corresponding z-average root-mean-square radii (Rz) for AMP ranged from 145 to over 300 nm. Low recoveries from the AF4 channel were found to be due primarily to the focusing step. The calculated mass percent of AMY and AMP from integrated RI peak areas agreed well with nominal values for the individual starch hybrids. Both qualitative and quantitative data were reproducible. The results show the AF4–MALS–RI method to be well suited for routine molecular characterization of starch.

Amylopectin structure of heat–moisture treated starches

AbstractThe effects of heat–moisture treatment (HMT; moisture content of 25%, at 100°C for 24 h) on starch chain distribution and unit chain distribution of amylopectin in normal rice, waxy rice, normal corn, waxy corn, normal potato, and waxy potato starches were investigated. After HMT, starch chain distribution (amylose and amylopectin responses) of waxy corn and potato starches were identical to those of untreated starches, whereas the chromatographic response of waxy rice starch showed a slight decrease, but with a slight increase in peak tailing. This result indicated that HMT had no (or very limited) effect on the degradation of amylopectins. Analysis of unit chain distribution of amylopectins revealed that waxy characteristics affected the molecular structure of amylopectin in untreated starches, i.e., the CL of normal‐type starches was greater than that of waxy‐type starches. After HMT, the CL and unit chain distribution of all starches were no different than those of untreated starches. The results implied that changes in the physico‐chemical properties of HMT starches would be due to other phenomena rather than the degradation of amylopectin molecular structure. However, the thermal degradation of amylopectin molecules of waxy starches could occur by HMT at higher treatment temperatures (120 and 140°C).

Relationship among the key enzymatic activities involved in starch synthesis and amylopectin chain distributions in developing wheat grain

The aim of this study was to investigate the relationship among the activities of the key enzymes involved in starch synthesis and the fine structure of amylopectin in non-waxy and waxy types of wheat. Amylose, amylopectin, and starch accumulation increased continuously after anthesis and increased as a sigmoid curve during the grain filling stage. The accumulation rates showed single-peak curves and all reached their peaks at 20 days after anthesis (DAA). Adenosine diphosphate glucose pyrophosphorylase (AGPP), soluble starch synthase (SSS), granule-bound starch synthase (GBSS), and starch-branching enzyme (SBE) activities each showed a single-peak curve during grain filling and peaked at 20 to 25 DAA. A significantly positive or positive correlation was observed between the amylose, amylopectin, and starch accumulation rates and the activities of the aforementioned enzymes. Different amylopectin chain contents changed continually during grain development and varied differently between the two types of wheat. Moreover, the AGPP, SSS, GBSS, and SBE activities exhibited a close correlation with the different chains of amylopectin. The result shows that starch biosynthesis depends on the coordinated effects of the said enzymes. The SSS activity was earlier detected and had an activity level higher than that of GBSS at the early grain filling stage. Moreover, amylose was not found at 5 DAA, while amylopectin had already appeared. Based on the results, amylopectin synthesis is suggested to precede amylose synthesis. Key words: Common wheat (Triticum aestivum L.), Key enzyme, Starch synthesis, Amylopectin structure.

Cellulose Nanocomposite Biopolymer Foam—Hierarchical Structure Effects on Energy Absorption

Starch is an attractive biofoam candidate as replacement of expanded polystyrene (EPS) in packaging materials. The main technical problems with starch foam include its hygroscopic nature, sensitivity of its mechanical properties to moisture content, and much lower energy absorption than EPS. In the present study, a starch-based biofoam is for the first time able to reach comparable mechanical properties (E = 32 MPa, compressive yield strength, 630 kPa) to EPS at 50% relative humidity and similar relative density. The reason is the nanocomposite concept in the form of a cellulose nanofiber network reinforcing the hygroscopic amylopectin starch matrix in the cell wall. The biofoams are prepared by the freezing/freeze-drying technique and subjected to compressive loading. Cell structure is characterized by FE-SEM of cross sections. Mechanical properties are related to cell structure and cell wall nanocomposite composition. Hierarchically structured biofoams are demonstrated to be interesting materials with potential for strongly improved mechanical properties.

Specific screening method for dextran and hydroxyethyl starch in human urine by size exclusion chromatography–in-source collision-induced dissociation–time-of-flight mass spectrometry

The use of plasma volume expanders (PVE), such as dextran (DEX) and hydroxyethyl starch (HES), is prohibited in sports. DEX is a naturally occurring glucose polymer, whereas HES is synthetically produced from amylopectin starch by substitution with hydroxyethyl groups. In doping control, the commonly applied enzymatic and colorimetric screening methods are lacking adequate specificity for DEX and HES. Also, gas chromatographic-mass spectrometic (GC-MS) screening methods have specificity issues with DEX. In addition, due to the nature of the target compounds, time-consuming derivatisation steps are required in GC-MS. Based on the high molecular weight of carbohydrate polymers excreted in urine after administration of DEX and HES, a screening method was developed involving size exclusion chromatography (SEC) combined with time-of-flight mass spectrometry (TOFMS). By using solely a SEC guard column as an analytical column allowed sufficient chromatographic resolution in a minimal amount of time and with reasonable repeatability (average RSD of 10%). Detector response was linear throughout the measurement range with R(2) > 0.99 for both analytes. Limits of detection were 100 and 250 μg mL(-1) for DEX and HES, respectively. Ion suppression was found to be 52% at maximum. In-source collision-induced dissociation (ISCID) was used to produce characteristic fragments at a mass accuracy better than 2 mDa. The specificity of the SEC-ISCID-TOFMS method was demonstrated with 120 PVE negative doping control samples analyzed in parallel with a routine GC-MS screening method. In addition, seven urine samples from diabetic athletes, causing interpretation problems in routine GC-MS, showed here a definitely negative profile.

Characterization of Copolymer Dehypon® LS 54 and Its Application for Aqueous Two-Phase Systems Paired with the Waxy Maize Starch for Protein Extraction

A thermo-separating aqueous two-phase system composed of Dehypon® LS 54, a polymeric surfactant and the waxy maize starch (amylopectin starch) has been used for partitioning of cutinase as a model protein. Dehypon® LS 54 were characterized by using 1H NMR spectroscopy to get information regarding the chemical structure and to confirm the presence of aliphatic moiety group in this copolymer. The phase diagram obtained for these novel polymer-polymers two-phase system shows two-phases with high polymer concentration. The waxy maize starch is enriched in the bottom phase while the copolymer Dehypon® LS 54 is found in the upper phase. Since this copolymer (Dehypon® LS 54) is thermo-reactive, the upper phase can be removed and heated above the copolymer’s cloud-point which resulting in the formation of a new two-phase system with a lower water phase, containing the target protein and an upper is copolymer-rich phase. Our results show that systems formed by waxy maize starch and Dehypon® LS 54 could become an alternative system to be used in large scale protein and enzyme purification due to their low cost, and also because they offer a viable solution to problems of polymer removal and recycling which makes this system more attractive.

Evaluation of Assam Bora Rice Starch as Plasma Volume Expander by Polymer Analysis

Water soluble polysaccharides are currently finding increasing use as a basis material for plasma volume expander. In clinical setting it is desirable to have a precise knowledge of steric and chemical structure, since these affect the pharmacokinetics and pharmacology of plasma volume expander. Branch component of starch amylopectin is very similar in structure to glycogen, the reserve polysaccharide of animal and therefore is liable to be compatible with body tissue. The knowledge of weight average molecular mass, degree of branching, osmotic pressure and coil dimension are essential, since low molecular mass do not have desirable effect and large molar mass have undesirable effect. Assam Bora rice starch was characterized by polymer analysis for use as plasma volume expander. Characterization involves the determination of FTIR spectra, degree of branching by H1 NMR, osmotic pressure by internal measurement technique, establishment of Mark-Houwink relationship and determination of Molecular weight - viscosity relationship.

Application of the Aqueous Two-phase Thermoseparating Systems of Dehypon® LS 54-the Waxy Maize Starch for Protein Extraction

A thermo-separating aqueous two-phase system composed of Dehypon� LS 54, a polymeric surfactant and the waxy maize starch (amylopectin starch), has been used for partitioning of cutinase as a model protein. The phase diagram obtained for this novel polymer-polymer two-phase system shows two-phases with high polymer concentration. The waxy maize starch is enriched in the bottom phase while the copolymer of Ethylene Oxide (EO) and Propylene Oxide (PO) is found in the upper phase. Since, this copolymer (Dehypon� LS 54) is the thermo-reactive, the upper phase can be removed and heated above the copolymer�s cloud-point resulting in the formation of a new two-phase system with a lower water phase containing the target protein and an upper copolymer-rich phase. Present results show that the systems were formed by the waxy maize starch and a copolymer Dehypon� LS 54 may be considered as an interesting alternative to be used in protein purification due to their low cost, in addition, they offer a viable solution to problems of polymer removal and recycling.

Estimating the helical pitch angle of amylopectin in starch using polarization secondharmonic generation microscopy

Starch granules are among the brightest natural second harmonic generation (SHG)converters. They basically consist of amylose and amylopectin molecules and the source ofthe SHG signal is still undetermined. In the present study we perform polarizationsensitive SHG (PSHG) imaging of wheat starch granules and we fit the SHGsignal variation of each pixel of the PSHG images into a generalized biophysicalmodel. By assuming that the SHG source molecule is a helix with cylindricalsymmetry along its long axis, the model extracts the helical pitch angle of the SHGsource for every pixel of the image. By displaying the pixel histogram representingthis helical pitch angle we found a highly peaked histogram with maximum atθe = 36.1° and awidth of Δθe = 9.3°. This pitch angle corresponds to the strand of the parallel double helical structure, calledamylopectin (as measured by a small angle x-ray scattering technique). This demonstratesamylopectin (and not amylose) as the source of SHG in starch. According to ourknowledge, this is the first estimation of the amylopectin’s pitch angle in starch usingPSHG.

Advances in Characterization of Amylose and Amylopectin Starch

As two major constituents of starch,amylose and amylopectin are distinct in both molecular structures and molecular aggregation,which results in dissimilarity in their physico-chemical properties.Consequently,the application performance of starch is variable due to the ratio of amylose and amylopectin.Current progress in characterization such as purity,molecular structure,relative molecular weight,crystal characteristics,thermal enthalpy and viscosity of amylose and amylopectin has been reviewed in this paper,which will provide meaningful references for further investigations of structural and physicochemical characterization as well as the application of amylose and amylopectin.

Isolation and Physicochemical Characterization of Assam Bora Rice Starch for Use as a Plasma Volume Expander

Water soluble polysaccharides are most effective oncotic agents which are used for treatment of intravascular volume deficiency. Nowadays, they are used as basic material for plasma volume expander. Plasma volume expander based on starch has lower tendency to remain in any major organ of body in comparison to other plasma volume expander. Branched component of starch amylopectin is very similar in structure to glycogen, the reserve polysaccharides of animal; for all this reason starch is compatible with body tissues. Physicochemical properties of raw starch and amylopectin, isolated from Assam Bora rice were characterized for use as plasma volume expander. Characterization involves the determination of ash value, weight average molecular mass, viscosity and resistance towards enzymatic (amylase) hydrolysis. Amylose content was almost negligible. The X-ray diffraction pattern of Assam Bora rice starch was typically A type. High degree of crystallinity of Assam Bora rice starch reflects its resistance towards enzymatic hydrolysis which is of therapeutic advantage for using it as a plasma volume expander.

Morphology and physicochemical properties of mechanically activated rice starch

The morphology and physicochemical properties of mechanically activated rice starch (MARS) isolated from three rice cultivars were investigated by scanning electron microscopy, X-ray diffractometry, gel permeation chromatography and Rapid Visco Analysis. The shape of rice starch granule changed from native polyhedron to anomalistic state during mechanical activation. It was suggested that the hydration of starch and moisture was an important factor for granules agglomeration which appeared more easily with higher moisture content. Mechanical force resulted in destroying of starch crystal structure which disappeared basically after activated for 10 h. As the mechanical activation time prolonged, the amylopectin and amylose of rice starch were both decomposed gradually, thus causing the increase of cold-water solubility and reducing power and the decrease of BV. Meanwhile, the pasting temperature and the viscosity of MARS decreased, including peak viscosity, final viscosity, breakdown viscosity and setback viscosity. The crystalline and molecular structure of rice starch with 6.02% moisture content were more easily destroyed by mechanical force than those with 1.05% and 11.05% moisture content, which resulted in higher cold-water solubility and reducing power, lower BV, pasting temperature, peak viscosity, final viscosity, breakdown viscosity and setback viscosity.

Macromolecular Changes in Extruded Starch‐Films Plasticized with Glycerol, Water and Stearic Acid

AbstractNative corn starch, plasticized with water, glycerol and stearic acid, was extruded in a conical twin‐screw extruder and sheeted into 0.4–0.6 mm thick films. The effects of extrusion and plasticizers on gelatinization, as well as the molecular and structural changes, in thermoplastic starch were analyzed. The onset and peak gelatinization temperatures of extruded starch varied from 42–46°C and 52.9–56.9°C, respectively, depending on the glycerol content. The enthalpy of gelatinization of extruded thermoplastic starch in excess water varied from 3.6–7.6 J/g, which also increased with plasticizer content. Amylose‐lipid complexes were formed during extrusion, and their enthalpies depended on the initial stearic acid and moisture contents. High‐performance size‐exclusion chromatography (HPSEC) data revealed that the starch underwent fragmentation during extrusion even under highly plasticized conditions, but the degradation was not severe as compared to previous findings. The relative percentages of amylopectin and amylose in native starch were 76.9 and 23.1%, respectively, which were changed to 71.3–76.6% and 23.4–28.7% in the extrudates. The average molecular weights of amylopectin and amylose in the extrudates ranged from 1.55×107–2.07×107 and 4.35×105–7.39×105, respectively. On the other hand, the molecular weights of amylopectin and amylose in native corn starch were observed as 2.27×107 and 4.68×105, respectively. Cross‐polarization magical angle spinning (CP/MAS) and high‐power decoupling (HP‐DEC) nuclear magnetic resonance (NMR) spectra of thermoplastic starch revealed the characteristics of amylomaize starch, confirming HPSEC results that the amylopectin macromolecules underwent fragmentation into amylose‐like fractions. In the extrudates, glycerol was found to be less mobile and entrained within the starch network.

Physicochemical Characteristics of Starches from Unripe Fruits of Mango and Banana

AbstractMango and banana starches were isolated from unripe fruits and their morphology; thermal and pasting properties; molar mass and chain length distribution were determined. Mango starch granules were spherical or dome‐shaped and split, while banana starch had elongated granules with a lenticular shape. Amylopectin of both fruit starches had a lower molar mass than maize starch amylopectin; however, mango amylopectin had the highest gyration radius. Banana amylopectin showed the lowest percentage of short chains [degree of polymerization (DP) 6–12] and the highest level of long chains (DP ≥ 37); mango amylopectin presented the highest fraction of short chains, but the level of longest chains was intermediate between those of banana and maize amylopectins. Banana starch presented the highest average gelatinization temperature followed by mango starch and maize starch had the lowest value; a similar pattern was found for the gelatinization enthalpy. The two fruit starches had a lower pasting temperature than maize starch, but the former samples showed higher peak and final viscosities than maize starch. Structural differences identified in the fruit starches explain their physicochemical characteristics such as thermal and pasting behavior.

Structure of a pullulanase from Bacillus acidopullulyticus

The industrial hydrolysis of polysaccharides continues to be of considerable interest and, with the drive towards green chemical processes and renewable sources of fuel, the enzymatic hydrolysis of plant carbohydrates is only set to increase. One of the most widely used plant derived polysaccharides are the starches; predominantly a-1,4 linked D-glucopyranoside polymers with, to varying degrees, a-1,6 branches. Complete starch hydrolysis requires a consortium of enzymes including endo-amylases, glucoamylases and a-glucosidases as well as diverse a-1,6 cleaving enzymes including ‘‘pullulanases’’. Many of these a-glucan active enzymes are found in the largest of the CArbohydrate-active enZYmes (CAZY) sequence families, family GH13 (see www.cazy.org1,2 recently reviewed in a historical context in Ref. 3). Considering the diversity of GH13 enzymes4 and their burgeoning applications in environmental-friendly processes, there remains a need to study these enzymes further particularly to probe their 3-D structures and often complex modular architectures. Here we report the 3-D structure, refined in two crystal forms at resolutions of 1.7 and 2.1 A, respectively, of a pullulanase from the bacterium Bacillus acidopullulyticus. The substrate, pullulan, is a polysaccharide in which repeating maltotriosyl units (a-1,4 linked) are joined through a-1,6 links, Figure 1. Pullulanases cleave the a1,6 links to liberate maltotriose. In industrial applications, these enzymes find use not merely for the breakdown of pullulan but also for the hydrolysis of the a-1,6 linkages in amylopectin starch. The B. acidopullulyticus enzyme (hereafter BaPul13A) thus finds commercial application in the starch industry where its ‘‘debranching’’ activity is utilized in the production of high fructose corn syrup5 and in the production of high maltose content syrups but also in the brewing industry, especially in the production of low calorie and ‘‘light’’ beers where it allows more complete attenuation (i.e., more complete fermentation of the mash and less residual sugar). The 3-D structure of BaPul13A was solved by single isomorphous replacement using an ‘‘in-house’’ uranyl derivative and subsequently refined in two different crystal forms. Pullulanases are frequently characterized by complex multi-domain architectures in which the catalytic module is appended to several carbohydrate-binding domains (CBMs) as well as many domains of unknown function (termed ‘‘X’’ modules). The structure of BaPul13a indeed forms an unusual domain organization, in which the N-terminal CBM41 domain is disordered/partially absent in-crystal but in which the X45a-X25-X45b-CBM48-GH13 multi-domain architecture is both clear and not, to our knowledge, previously observed. Comparison with the known Klebsiella pneumoniae pullulanase6 and the pullulanase/debranching enzyme from Bacillus subtilis reveals a conserved active centre and similar polysaccharide binding surfaces consistent with a1,6 hydrolase activity within the a-amylase fold.

Effects of annealing on gelatinization and microstructures of corn starches with different amylose/amylopectin ratios

Corn starches with different amylose/amylopectin ratios (waxy 0/100, normal corn 23/77, Gelose 50 50/50, Gelose 80 80/20) were annealed at below their gelatinization temperatures in excess water. The effects of annealing on the gelatinization and microstructures of the starches were studied using DSC, XRD and a microscope equipped with both normal and polarized light. In addition, a high-pressure DSC pan was used to study the effects of high-temperature annealing on the multiphase transitions of starches with different water contents. The granular size of the starches increased after the annealing process, but the size variation rates were different, with higher amylopectin contents resulting in a higher diameter growth rates and final accretion ratios. DSC results showed that annealing increased the gelatinization enthalpy of the amylose-rich starches. The increased enthalpy was mainly attributed to endotherm G – there were no significant changes to endotherms M1, M2 or Z – indicating that annealing mainly affected the helical length of shorter or sub-optional amylopectins, in particular the amylopectin in amylose-rich starches. The XRD traces of all starches after annealing remained unchanged.

Effect of annealing and pressure on microstructure of cornstarches with different amylose/amylopectin ratios

This work focuses on the effect of annealing and pressure on microstructures of starch, in particular the crystal structure and crystallinity to further explore the mechanisms of annealing and pressure treatment. Cornstarches with different amylose/amylopectin ratios were used as model materials. Since the samples covered both A-type (high amylopectin starch: waxy and maize) and B-type (high amylose starch: G50 and G80) crystals, the results can be used to clarify some previous confusion. The effect of annealing and pressure on the crystallinity and double helices were investigated by X-ray diffraction (XRD) and 13C CP/MAS NMR spectroscopy. The crystal form of various starches remained unchanged after annealing and pressure treatment. XRD detection showed that the relative crystallinity (RC) of high amylopectin starches was increased slightly after annealing, while the RC of high amylose-rich starches remained unchanged. NMR measurement supported the XRD results. The increase can be explained by the chain relaxation. XRD results also indicated that some of the fixed region in crystallinity was susceptible to outside forces. The effect of annealing and pressure on starch gelatinization temperature and enthalpy are used to explore the mechanisms.

Effects of structure and modification on sustained release properties of starches

Starches of different sources and compositions were investigated to determine the effect of structure and chemical modification on the sustained release properties of the resultant modified starches. Starches were cross-linked with epichlorohydrin and substituted with carboxymethyl or aminoethyl groups at different levels. Substitution efficiency was overall higher for waxy corn and potato starches than for Hylon VII, and was higher for starches at low cross-linking levels than those at high cross-linking ones. Waxy corn starch displayed better sustained release properties when cross-linked to a lower level, whereas Hylon VII showed better performances when cross-linked to a higher level. Matrices substituted with carboxymethyl and aminoethyl groups at the high level showed better sustained release properties than those substituted at the low level. The proportion and structure of amylose and amylopectin in starches from different botanical sources strongly influenced the level of modification required to produce a satisfactory sustained release matrix.

Structure and Functional Properties of Sorghum Starches Differing in Amylose Content

Starches were isolated from grains of waxy, heterowaxy, and normal sorghum. To study the relationship between starch structure and functionality and guide applications of these starches, amylose content, amylopectin chain-length distributions, gelatinization and retrogradation, pasting properties, dynamic rheological properties, and in vitro enzyme digestion of raw starches were analyzed. Heterowaxy sorghum starch had intermediate amylose content, pasting properties, and dynamic rheological properties. Stress relaxation was a useful indicator of cooked starch cohesiveness. Cooked heterowaxy sorghum starch (10% solids) had a viscoelastic-solid type of character, whereas cooked waxy sorghum starch behaved like a viscoelastic liquid. Amylopectin of normal sorghum starch had a slightly higher proportion of chains with degree of polymerization (DP) of 6-15 (45.5%) compared with amylopectin of heterowaxy starch (44.1%), which had a gelatinization peak temperature 2 degrees C higher than normal sorghum starch. Heterowaxy sorghum starch contained significantly lower rapidly digestible starch (RDS) and higher resistant starch (RS) than waxy sorghum starch.