Amylopectin Fraction Research Articles

Comparison of fourier transform mid infrared spectroscopy and near infrared reflectance spectroscopy with differential scanning calorimetry for the study of the staling of bread

AbstractThe staling of bread has previously been studied by differential scanning calorimetry and by simple rheological measurements. In this collaborative study, two spectroscopic techniques (Fourier transform mid infrared spectroscopy and near infrared reflectance spectroscopy) have been used in addition to differential scanning calorimetry to follow the progress of bread staling. Using each technique, changes in measured properties were apparent which, when fitted by first order exponential equations, gave calculated rate constants of similar magnitude. It is postulated that each technique gives independent information about the crystallisation process in the amylopectin fraction of the bread crumb.

Fine Structure of Mung Bean Starch: An Improved Method of Fractionation

AbstractLaboratory isolated mung bean starch was fractionated into its amylose and amylopectin components using a modified procedure. The resulting products were shown to be both homogeneous and more susceptible to the hydrolyzing enzymes commonly used for structural analysis. The fine structure of the fractions was investigated using hydrolytic enzymes, chemical analysis and gel filtration chromatography. Differences in amylose/amylopectin fractions isolated by the modified and conventional extraction procedures were apparent. The unit chain length of amylopectin, DPn and limiting viscosity number of amylose were all lower for samples isolated by the modified method. In contrast the enzymatic hydrolysis of both the amylose and amylopectin fractions was improved for the material extracted by the modified method, low levels of branching and a unit chain distribution by gel filtration chromatography of the two overlapping populations with average degree of polymerization of 42 and 14 was obtained.

The effect of pH and NaCl content on starch gel ageing. A study by differential scanning calorimetry and rheology

Rheological (large deformation Instron measurements) and thermal (differential scanning calorimetry, DSC) techniques have been applied to study the ageing of starch gels (volume fraction of water v1 0·61, 51 %) in the range of pH 4·4-9·4 (ionic strength, I ⩽, 0·1) or salt content 0-4-43 % (NaCl, I = 0-1·48) for 20 days at 21 °C. All gels exhibited increases in `elastic modulus' and peak stress with storage time, while DSC showed the development of a `staling endotherm' S, associated with re-ordering of amylopectin. The data were analysed by fitting Avrami equations to each data-set via the method of non-linear least squares. The addition of buffers to control (no-salt) gels significantly affected the kinetics of theological and thermal changes during ageing, but differences in pH had little further effect. Generally, increased salt concentration reduced the rate constants for development of both theological parameters during gel ageing. For both buffered and control gels the developing S endotherm (range 41·2-71·4 °C) was monophasic. Gels with salt showed an additional peak at higher temperatures whose limiting size AL was proportional to salt content. AL values and rate constants, for both first peak and the combined endotherm, were inversely related to salt content, indicating that salt inhibits the re-ordering of the amylopectin fraction of starch gels during ageing. The observation of a biphasic endotherm suggests that salt induces the separation of domains within this fraction.

Estimation and fractionation of the essentially unbranched (amylose) and branched (amylopectin) components of starches with concanavalin A

Conditions have been devised for the quantitative precipitation of the branched fraction in starches by concanavalin A and the enzymic estimation of the α- d-glucan in this and the soluble components. For some starches, such as those from cereal and high-amylose pea seeds, the percentage of branched fraction determined by this procedure was higher than that calculated by deducting from one hundred the apparent amylose content as measured by potentiometric iodine titration, suggesting a method for estimating the content of material having an atypical structure in the whole starch. The procedure has been adapted to provide a preparative method of separating amylose and amylopectin fractions. It efficiently separated these in starches that cannot be fully fractionated by complexing with 1-butanol, such as those from high-amylose pea seeds and tobacco leaves.

Effect of Starch of Textural Properties of Surimi Gel

ABSTRACTThe proportion of amylose and amylopectin, and the rheological behavior of eight starches were correlated with the textural properties of starch‐containing surimi gels. Findings included the following: increased firmness and cohesiveness with increases in water‐holding ability and viscosity of the starch; increased expressible moisture and penetration force with an increase in the amylose fraction due to increased retrogradation: increased tensile force with an increase in the amylopectin fraction: and increased cohesiveness and chewiness after refrigerated storage for all starches with a greater increase for high amylose starches. Surimi gels containing potato starch were the firmest and most cohesive. The textural properties of starch‐containing surimi gel correlated well (r = 0.90 to 0.97, P>0.05) with the viscosity of starch paste if 100% amylopectin‐containing and pregelatinized starches were excluded from the correlation.

Xerophytic Gourd Root Starches. Part V: Structural Characteristics, Gelatinization Properties and Rheologic Behavior of Coyote Gourd Starch (Cucurbita digitata Gray)

AbstractAs part of a continuing study of xerophytic cucurbit starches, coyote gourd (Cucurbita digitata Gray) root starch and starch components have been examined. Coyote gourd amylose and amylopectin fractions were highly susceptible to β‐amylolysis; average degree of polymerization and average unit chain lengths of the latter material intimated the large size and multiply‐branched asymmetrical structure of the molecules. The isolated granules were small, spherical or irregular in shape and birefringent. Crystalline regions of native granules evinced a B‐type diffraction pattern which was altered to that of the C‐type by treatment with moist heat. Gelatinization characteristics, restricted swelling and low solubility of the subject material suggested a highly organized granule architecture. Gelatinized suspensions formed stiff opaque gels upon cooling which were resistant to deformation. A strong degree of association among granule components was also evident in the rheologic behavior of the material. In general, the effects of suspension concentration, acidity and sucrose upon the rheologic performance of this material were predictable from known behavior of standard starches; the addition of salt or oil resulted in increased pasting temperatures and had variable influence upon suspension viscosities.

澱粉の結合リン酸とアミラーゼ作用

The actions of amylases in the vicinity of the phosphate groups at C-3 and C-6 of the glucosyl residues of potato starch and the locations of the phosphate groups in the starch, which were determined by analyses of the phosphorylated products, were summarized.Sweet potato β-amylase and Aspergillus niger glucoamylase cleaved the (1→4)-α-D-linkage of the 6-phosphorylated residue at the non-reducing side but not that of the 3-phosphorylated one, leaving at least one glucosyl residue attached to the 3-phosphorylated one. α-Amylases from various origins cleaved different sites in the vicinity of the 3- and 6-phosphorylated residues, that is, the enzymes from Bacillus subtilis, porcine pancreas and Aspergillus oryzae produced 32-phosphoryl maltotetraose (32-PG4) and 62-phosphoryl maltotriose (62-PG3), 32-PG4 and 63-phosphoryl maltotriose (63-PG3), and 32-PG4 and 63-PG3, respectively, upon exhaustive hydrolysis. The phosphate group at C-6 was as obstructive as the branch linkage of amylopectin, but less obstructive than the phosphate group at C-3. Their inhibitory behavior seemed to reflect a bulk rather than an electronegative effect.Most phosphate groups were found in the amylopectin fraction. The results of analyses of phosphorylatedbranched- and unbranched-chains produced from potato amylopectin on exhaustive β-amylolysis followed by isoamylolysis indicated that the phosphate groups were located mostly in B-chains (chains with side chains) and largely on the outer section of chains of amylopectin, except in the vicinity of the branch linkages.

Varietal Differences in Properties Among High Amylose Rice Starches

AbstractAmong three high‐amylose starches differing in gel consistency, the hard gel starch (IR42), corresponding to harder cooked rice, had higher amylograph consistency and setback, higher gel viscosity in 0.2 N KOH and higher alkali viscograph peak than starch with soft (IR32) or medium (IR36) gel consistency. IR42 starch had less extractable starch and amylose in boiling water than IR32 and IR36 starches. The three starches had similar amyloses; the differences in gel consistency were due to the amylopectin fraction. IR42 amylopectin had higher iodine affinity, more long‐chain linear fractions on isoamylase debranching and gel filtration or 1‐butanol precipitation, and less DPn 16–17 fraction than IR32 and IR36 amylopectins.

Tepary Bean Starch. Part I. Physico‐chemical Properties

AbstractStarch of high purity was isolated by a simple procedure from tepary beans (Phaseolus acutifolius var. latifolius). Granules were spherical to oval with a birefringence pattern similar to that of other legume starches. Under SEM they appeared smooth with no evidence of fissures. They showed a normal distribution of diameters with a range of 15.5–59.8 μ and a mean of 33.5 μ. Tepary starch had an amylose content of 30.7% and a gelatinization temperature range of 70.5–84.0°C. Other properties were also determined. Fractionation provided an amylose fraction with a β‐amyloysis limit of 76.3% and an average DPη of 618. The amylopectin fraction had an average magnified image values of 33, 22 and 10 glucose units respectively.

A Comparative Study of the Effect of Acetylation on Starches of Phaseolus vulgaris Biotypes

AbstractEnzyme hydrolysis, X‐ray diffraction, differential scanning calorimetry and Visco/Amylo/Graphy were used to examine the strength of associative bonding forces between starch chains of native legumes. Addition of acetic anhydride resulted in unequal degrees of substitution. Scanning electron microscopy revealed no differences between the external morphology of native and acetylated starches. Similarities in the X‐ray diffraction patterns of native and acetylated starches indicated that acetyl groups mainly entered the amorphous regions. On acetylation, decreases in starch hydrolysis, gelatinization temperatures, enthalpies of gelatinization, extent of viscosity increase during the holding period at 95°C and syneresis, and increases in 95°C viscosity, set‐back and amylose exudation were observed. It appeared the extent of distribution of the acetyl groups between the amylose and the amorphous regions of the amylopectin fraction varied among legume biotypes, and differences existed between legume starches with regard to the ratio of the concentration of the acetyl group at the 2—O position relative to that at 6—O.

Degradation of Wheat Starch in a Single Screw Extruder: Characteristics of Extruded Starch Polymers

ABSTRACTWheat starch was processed in a 19 mm diameter, single screw extruder to study the physical and structural modifications that occur during extrusion cooking. Structural modification of the starch polymers was investigated using gel permeation chromatography (GPC), enzymatic digestions and dilute solution viscometry. Both the GPC and intrinsic viscosity results showed that the average molecular size significantly decreased as a result of extrusion processing. The relative amount of material excluded by Bio‐Gel A150m was considerably lower for extruded samples than for unprocessed wheat starch and this size reduction of the amylopectin fraction was attributed to mechanical rupture of covalent bonds. The characterization of the structural modifications of the starch polymers is reported.

Molecular weight-viscosity relationship for amylopectin, a highly branched polymer

Rate of acid hydrolysis of amylopectin is discussed from molecular weight variation; a two step mechanism is found. The highly branched amylopectin fractions obtained by partial acid hydrolysis allow experimental determination of Mark-Houwink's law exponents. Theoretical and experimental “a” values are compared.

A kinetic study of bread staling by differential scanning calorimetry and compressibility measurements. The effect of added monoglyceride

Inclusion of glyceryl monostearate (GMS), in the gel-state, as a dough constituent had a significant and clearly measurable effect upon the ageing of bread observed by both differential scanning calorimetry (DSC) and crumb compressibility measurement. Using DSC, a reduction in the rate of development of the ‘staling endotherm’, S, was observed in GMS-containing bread compared with control bread. Inclusion of GMS led to an increase in the size of the M2 endotherm associated with melting of the amylose-monoglyceride complex. The results were in agreement with a model, in which addition of GMS led to a reduction in the rate constant for development of the S endotherm (kD) but which had no effect upon the limiting value AL. This suggested that the S endotherm was due to crystallisation of the amylopectin fraction of the starch. From measurements of crumb compressibility it was concluded that the addition of GMS, as well as increasing loaf volume, also led to a reduction in the rate constant for crumb firming (kc). This suggested that GMS had an effect within the crumb of bread during ageing and did not operate solely by increasing loaf specific volume.

Branching enzyme from amylomaize endosperms

Branching enzyme [(1→4)-α- d-glucan:(1→4)-α- d-glucan 6-glucosyltransferase, EC 2.4.1.18] from developing amylomaize endosperms was fractionated by precipitation with ammonium sulfate and separated into two forms by chromatography on DEAE-cellulose. One form was purified to homogeneity, and found to be primarily monomeric with a broad pH-optimum (pH 6.5–8.0), a low activity in Tris-HCl buffer, and a molecular weight of ∼90,000. These properties were similar to those of a branching enzyme from normal maize kernels previously described. The purified enzyme was apparently inhibited by a low concentration of mercury(II) chloride and increasing concentrations of citrate. The K m value of the enzyme was 18 μg/mL for potato amylose. Further purification of another form of amylomaize branching-enzymes implied the possible presence of additional proteins having molecular weights of ∼92,000 and ∼45,000. The total content of branching enzyme in amylomaize endosperm was approximately one-third of that present in normal maize during endosperm development. The results suggest that amylomaize endosperms may contain at least three forms of branching enzyme, and that the decreased content of amylopectin fraction in amylomaize starch may be associated with the decrease in the total content of branching enzyme.

Properties of Residual Starches of Sugary‐2 and Sugary‐2 Opaque‐2 Maize Following Amylase Hydrolysis

AbstractProperties of residual starches of sugary‐2 opaque‐2 and sugary‐2 maize starch granules hydrolyzed with glucoamylases were investigated. A crude and two crystalline glucoamylases were used. The amylopectin fractions of both starches hydrolyzed easier than that of amylose with all enzymes. Residual starches hydrolyzed by the crude glucoamylase accumulated low‐molecular weight materials, which was not observed in residual starches attacked by crystalline glucoamylase. It was suggested that in the crude enzyme the contaminating α‐amylase caused the accumulation of the minified fraction. It is also suggested that the crystalline region of sugary‐2 opaque‐2 starch may consist of a mixture of A‐type and B‐type patterns. Evidence for this was from observation of the changes in X‐ray diffraction patterns of residual starch following amylase and acid hydrolysis.

PHYSICOCHEMICAL CHARACTERISTICS OF YAM STARCHES

Starch from tubers of Dioscorea alata, Dioscorea cayenensis, Dioscorea dumetorum, and Dioscorea rotundata was isolated and some of the important characteristics determined. Amylose and amylopectin fractions were obtained by aqueous leaching technique. All the starches appeared to have definite but minor differences in iodine binding capacity, swelling power, solubility, intrinsic viscosity, and amylose/amylopectin ratio. Brabender amylogram of each starch showed no distinct peak viscosity, and the general amylograph pattern was distinctly different from typical amylographs of cereal starches. Amylose fractions from each starch variety exhibited variable degree of β-amylolysis limits ranging from 92–97.5%, and an average molecular weight for amylose triacetate of 210,000 to 265,000. Amylopectin fractions subjected to debranching by pullulanase gave essentially two chain populations of polysaccharides with degree of polymerization of approximately 13–27 and 47–65, respectively. Average unit chain length of the amylopectins ranged from 19 in Dioscorea rotundata to 24 in Dioscorea dumetorum.

Evidence for Independent Genetic Control of the Multiple Forms of Maize Endosperm Branching Enzymes and Starch Synthases

Soluble starch synthase and starch-branching enzymes in extracts from kernels of four maize genotypes were compared. Extracts from normal (nonmutant) maize were found to contain two starch synthases and three branching enzyme fractions. The different fractions could be distinguished by chromatographic properties and kinetic properties under various assay conditions. Kernels homozygous for the recessive amylose-extender (ae) allele were missing branching enzyme IIb. In addition, the citrate-stimulated activity of starch synthase I was reduced. This activity could be regenerated by the addition of branching enzyme to this fraction. No other starch synthase fractions were different from normal enzymes. Extracts from kernels homozygous for the recessive dull (du) allele were found to contain lower branching enzyme IIa and starch synthase II activities. Other fractions were not different from the normal enzymes. Analysis of extracts from kernels of the double mutant ae du indicated that the two mutants act independently. Branching enzyme IIb was absent and the citrate-stimulated reaction of starch synthase I was reduced but could be regenerated by the addition of branching enzyme (ae properties) and both branching enzyme IIa and starch synthase II were greatly reduced (du properties). Starch from ae and du endosperms contains higher amylose (66 and 42%, respectively) than normal endosperm (26%). In addition, the amylopectin fraction of ae starch is less highly branched than amylopectin from normal or du starch. The above observations suggest that the alterations of the starch may be accounted for by changes in the soluble synthase and branching enzyme fractions.

The silica content of plant polysaccharides

AbstractAnalysis of several plant polysaccharides confirmed the presence of silica (Si) in all pectin samples analysed and revealed its presence in potato starch. In the latter case the Si was concentrated in the amylopectin fraction. The range of Si values found, based on dry weight of polysaccharide analysed, was: (a) for pectin 1.40‐2.30; and (b) for potato starch 0.47‐0.80 mg g−1. Other samples analysed contained less than 0.10 mg g−1. It would appear that most of the Si present in potato tubers is located in the starch grain where its distribution parallels that of phosphorus (P). The comparable range of values found for P in potato starch was 1.30‐1.60 mg g−1. It is thus possible that some of the distinctive properties of potato starch attributed to P could be influenced by the Si present.

Effect of Gene Dosage at High Amylose Loci on the Properties of the Amylopectin Fractions of the Starches

AbstractThe effect of gene dosage at the amylose‐extender (ae) locus of maize and the rigosus‐a (ra) locus of peas on the amylopectin fraction of endosperm and cotyledon starch were examined. Amylopectin fractions were isolated by gel filtration, butanol complexing and a combination of the two methods. In general, increasing doses of the recessive allele at either locus resulted in amylopectin fractions with iodine spectra with absorption maxima at higher wavelengths and greater absorptivity. Starches from endosperm of differing ae dosage but homozygous waxy were found to contain no amylose by gel filtration. By debranching with pullulanase, these starches were shown to have increasing average chain length with increasing ae dosage. Additional data suggested that increasing dosage at the ae locus (regardless of the genotype at the waxy locus) or the ra locus resulted in amylopectin with increasing linearity. In addition, short chained amylose (approximately 100 glucose units) was observed in all ae genotypes in a homozygous Waxy background and all ra genotypes.

Changes in Some Properties of Starch Granules of Maize Having Amylose‐extender Gene by Amylase Attack

AbstractProperties of residual starch by glucoamylase attack were investigated in starch granules of maize (Zea mays L.) of amylose‐extender (ae) type (commercial “High Amylose‐7”; HA‐7). As increasing extent of hydrolysis, the amylose and amylopectin fractions decreased and low‐molecular‐weight materials were accumulated. Decrease in absorption intensity and sift to a range of shorter wavelength in γmax. of absorption spectra of iodine‐starch complexes were observed. The minified fractions had a peak of about 22 average glucose‐units and were nearly linear chains. It was suggested that the minified materials consisted of portion resisted to amylases in starch granules according to hydrolysis curves by glucoamylase. The fractions concerned to crystalline area of ae starch were suggested from X‐ray diffraction patterns.