Proportion Of Amylose Research Articles

Factors Affecting the Porridge-Making Quality of South African Sorghums

Research was undertaken to facilitate the breeding and selection of sorghums with both good milling and good porridge-making characteristics. Twenty seven cultivars were grown in the same locality under rainfed and supplementary irrigation conditions. The two measures of milling quality, abrasive hardness index and Brabender hardness (BH) were significantly correlated (P⩽0·001) in all sample sets; ie all data, rainfed samples and supplementary irrigation samples. The genetic basis of kernel hardness was confirmed as the hardest and softest cultivars were the same under both cultivation conditions. For all three sample sets there was a significant negative correlation (P⩽0·05) between kernel hardness according to BH and pasting peak viscosity (PPV). PPV is of importance as consumers prefer stiff porridges. The negative correlation between BH and PPV indicates that to select sorghum cultivars with good milling and good porridge-making quality, both kernel hardness and PPV need to be assessed. The sorghums produced under supplementary irrigation were softer according to BH, had higher PPV and set-back viscosity, and the starch contained a higher proportion of amylose than those produced under rainfed conditions. Thus, cultivation environment as well as genetics has a major effect on sorghum milling and porridge-making quality. © 1997 SCI.

The chemical structure of amylose and amylopectin fractions of starch from tobacco leaves during development and diurnally-nocturnally

Starches, isolated from rapidly expanding tobacco leaves four times during the day and night and once from fully expanded leaves, were fractionated with concanavalin A. From an examination of the amounts and properties of amylose, the diurnal decrease in iodine absorption of the starches on illumination appeared to be due to an increase in its branched character, and possibly the presence of unbranched polymer of low dp, combined with a decrease in the proportion of amylose fraction. The increase in apparent amylose content with age was due to an increase in the proportion of amylose. The amylose fractions at different times had only small differences in average mol size in solution and relative mol wt ( M r near 4 × 10 5) which were lower than those of storage organs. The average mol size in solution and relative mol wt of the amylopectins decreased during illumination, increased in darkness, and were lower ( M r 2–2.7 × 10 6) at all times than those from storage organs. Debranching followed by size-exclusion chromatography [on Fractogel TSK 50(S)] gave similar proportions of long, medium, and short chains for all amylopectin samples, and these proportions differed from those for debranched amylopectin from n-maize seed starch. On debranching and chromatography of the amylopectin β-limit dextrins (which gives an estimate of the proportions of core chains) differences persisted. Structural characteristics of amylopectin from tobacco leaf starch were similar to those of normal genotypes from storage organs. The proportion of glucosyl units in core chains, the external-to-core chain ratio, and indices of compactness were calculated for a number of (1 → 4)(1 → 6) α-glucans. A plot of the index of compactness for glycogens and amylopectins showed that the decrease in compactness and the increase in total average chain length that occurs from glycogen to normal and then to amylose extender amylopectins involves a proportionate increase in average internal, external, and core chain lengths and not a selective increase in one type of chain.

An analysis of seed development inPisum sativumXIX. Effect of mutant alleles at therandrbloci on starch grain size and on the content and composition of starch in developing pea seeds

The effects of mutant alleles at the r and rb loci on starch grain size and the levels of starch and amylose in developing pea (Pisum sativum L.) seeds have been examined. Four lines, near-isogenic except for genes at these loci, have been used to show that both mutations reduce levels of starch throughout embryo development and reduce levels still further when combined in the 'double mutant'. The reduction in starch content was due, at least in part, to a reduction in starch granule size. Although the proportion of starch in mature embryos was similar in the rrRbRb and RRrbrb lines, the starch content differed between these two lines during development, as a percentage of embryo dry weight. This difference was due to a reduction in the absolute growth of the embryo caused by the rb mutation. Lines homozygous for the mutant r allele with either wild-type (RbRb) or mutant (rbrb) alleles at the rb locus contained increased proportions of amylose in their starch throughout development, due to a reduced production of amylopectin. The presence of the rb mutation, however, also reduced the amount of amylose in relation to the reduction in total starch levels. Mutant alleles at both loci also reduced starch levels in the testa during development, the reduction due to rb being more extreme. Reciprocal crosses showed a maternal effect of the rb mutation on final seed size and on the absolute amount of starch in the embryo.

A comparative study of the effect of sugars on the thermal and mechanical properties of concentrated waxy maize, wheat, potato and pea starch gels

A comparative study was undertaken to examine the effect of sugars on the thermal and mechanical properties of ageing waxy maize, wheat, potato and pea starch gels. The addition of sugars, at a ratio of 1:0.5:1.5 ( w w ) for starch-sugar-water mixtures, inhibited chain reorganization in starch gels, as followed by differential scanning calorimetry and dynamic rheometry in the order, ribose > sucrose > maltotriose > water alone, glucose > fructose. Kinetic experiments on the evolution of storage modulus ( G′) at 8 °C indicated a progressive transition from a sigmoid curve (waxy maize) to a hyperbolic G′ — time relationship (potato and pea starches), consistent with an increasing proportion of amylose in the composite gels. The effects of sugars on the development of the retrogradation endotherm ( ΔH) and gel rigidity ( G′) were less pronounced for potato and pea starches than for waxy maize or wheat starches, presumably because of their higher amylose content, which dominates the gel network properties.

Crystalline Parts of Three Different Conformations Detected in Native and Enzymatically Degraded Starches

AbstractWe examined cereals and legume starches with different amylose contents, using X‐ray wide‐angle scattering. The parts of polymorphs in the crystalline regions and the crystallinity of the starches were determined. The high‐amylose starches hold 74.6%‐84.6% B‐type and 15.4%‐22.6% VH‐type.Crystallinity of high‐amylose starches is xc = 0.154–0.17. According to phase analysis of the scattering curve of wheat starch 6.8% B‐type and 93.2% A‐type are contained. Thus, in the crystalline phase wheat starch is more heterogeneous than maize starch. The residuary substance of heterogeneous hydrolysis of wheat starch at T1 =58°C is an insoluble sediment, which does contain already 17.1 % VH‐Amylose. This is the proof of the amylose‐lipid complex in the sediment. If the temperature of hydrolysis raised to 70°C, the VH,‐amylose proportion increased to 80.5%. Since the crystalline VH‐ structures are detectable during heterogeneous hydrolysis as from T1 = 58°C, they seem to have contained already in native starch.

Modification of starch granules by hydrolysis with hydrochloric acid in various alcohols, and the formation of new kinds of limit dextrins

Potato starch was treated severally in methanol, ethanol, 2-propanol, and 1-butanol with 0.36% and 6.0% HCl at 25°. The average d.p. dropped rapidly for starch treated with 0.36% acid and reached a limiting value within 24 h. For the treatment with 6.0% acid, the limiting value was reached between 30 and 75 h. The limiting d.p. progressively decreased in the sequence methanol > ethanol > 2-propanol > 1-butanol, and also decreased with an increase in the concentration of the acid. The amylose and the amylopectin fractions were isolated from the modified starches, and their average d.p. and proportions were determined. The amylopectin fractions were analyzed by gel-permeation chromatography on Bio-Gel A-5m, before and after isoamylolysis, and the amylose fractions were analyzed on Bio-Gel A-0.5m. The above starch products represent a new type of limit dextrins that have different average d.p., chain-length distributions, and proportions of amylose and amylopectin. These differences represent variable susceptibilities of the glycosidic bonds to hydrolysis when the starch granules are placed in different alcohols with different concentrations of acid.

Structural changes during development in the amylose and amylopectin fractions (separated by precipitation with concanavalin A) of starches from maize genotypes

The starches from four maize genotypes (waxy, normal, amylose-extender, and ae ae/wx wx) have been sampled at three stages of development, and fractionated by precipitation of the amylopectin with concanavalin A. The resulting amylose and amylopectin fractions were examined by gel chromatography before and after treatment with debranching enzyme. Both mature and immature samples were efficiently fractionated. The proportion of amylose in the starches of the n and ae genotypes, measured by concanavalin A precipitation, increased on development. A small proportion of the ae/wx mutant starch was not precipitated by concanavalin A, and its properties were those of an “intermediate fraction” of low molecular weight with a degree of branching and average chain-length intermediate between amylose and amylopectin. The amylose of n starch increased in molecular size during development, whereas that of ae decreased. No differences in molecular size and chain-length distribution were detected within a genotype for the amylopectins of wx, n, and ae/wx starches during development, but the component from ae starch decreased in molecular size and increased in average chain-length. Comparison of the amylopectins from wx, n, and ae starches showed a decrease in molecular size and an increase in average chain-length, in that order.

Amyloplastenentwicklung und Stärkesynthese in Samen von Futter- und Markerbsen

Development of amyloplasts and starch synthesis in seeds of field and garden peas Amyloplast development and changes in starch and amylose content in seeds of field and garden peas (Pisum sativum ssp. sativum and ssp. medullare) was studied from flowering to maturity in view of a possible relationship between amyloplast form and starch composition. Starch and amylose contents increased at different rates in both subspecies. In field peas starch content had reached the maximum (44 % in DM) 26 days after flowering with 45 % amylose in total starch. In garden peas, 25 days after flowering, starch content had only reached half of its maximum (32 % in DM) with an extremely high amylose proportion (88 %). At that growth stage form and size of amyloplasts were similar in both subspecies. There seems to be no tight relationship between form of amyloplasts and proportion of amylose in total starch. But then, when amyloplasts abruptly increased in size those of garden peas disrupted suddenly. This disruption is not due to a high amylose content. Because in a cross-breeding of field and garden peas, which was also investigated, the amyloplasts had remained intact irrespective of a high amylose proportion (63 %). The disruption may be due to differences in arrangement of starch molecule and in structure of plastid envelope.

Complexes of starch polysaccharides and poly(ethylene co‐acrylic acid): Structural characterization in the solid state

AbstractThe structural characterization of model complexes of amylose (AM) and amylopectin (AP) with poly(ethylene‐co‐acrylic acid) (EAA) was undertaken in order to better understand the interactions that occur between the polysaccharides and EAA in starch‐EAA‐polyethylene films. X‐ray diffraction and CP/MAS 13C‐NMR studies showed that precipitates from solution mixtures of AM and EAA form crystalline, helical V ‐type inclusion complexes. The proportion of AM forming the V ‐type complex in the EAA/AM blends, estimated from shifts in the C1 resonance of AM, increased with increasing EAA/AM ratio, reaching a value of about 80% at EAA/AM = 0.5 (w/w). Similar measurements for EAA/AP complexes showed < 10% V structure. Approximately 80% of the AM and 4% of the AP in these blends was resistant to amylase digestion, in good agreement with their V ‐structure contents as determined above. Resonances at 184 and 181 ppm were observed for the carboxyl carbon of EAA in the EAA/AM and EAA/AP complexes. The resonance at 181 ppm, which was not observed in pure EAA, probably reflects greater shielding of the carboxyl inside the polysaccharide helix as well as changes in hydrogen bonding. The intensity of this peak was 2–3 times larger for the EAA/AM than for the EAA/AP complexes. FTIR experiments suggest that most (> 50%) of the EAA carboxyl groups were hydrogen bonded to polysaccharide hydroxyl groups in both AM and AP complexes when EAA/polysaccharide < 1.

Isolation and Molecular Composition of Starch from Roots of Medicago sativa L.

AbstractThe concentration and molecular composition of starch from alfalfa (Medicago sativa L.) taproots were determined using dimethyl sulfoxide (DMSO) extraction and gel permeation chromatography. Three 24‐h extractions with 90% (v/v) DMSO were required to solubilize an average of 97% of the starch from freeze‐dried root tissues. Amylopectin comprised approximately 80% of starch isolated from alfalfa roots. The relative proportions of amylose and amylopectin were similar among three diverse alfalfa germplasms and one cultivar even through starch concentrations ranged from 20 to 410 g kg−1 dry weight. Elution profiles of debranched starches from alfalfa taproots contained two pools of low molecular weight chains with degrees of polymerization similar to debranched starches from maize (Zea mays L.), and potato (Solanum tuberosum L.). The molecular composition of starches from these alfalfa germplasms was similar to that commonly observed for most starches from cereals and tubers.

Composition of the seeds of some Amaranthus species

AbstractThe seeds of the five commonly consumed Amaranthus species have been analysed for their chemical composition and starch characteristics. A notably high fat, protein and ash content in the seeds of a sample of A. teunifolious as compared with other species has been demonstrated. All the samples analysed had a high oxalate and phytic acid content. The size of the starch granules from all the samples was in the range 08.2.3μm and the circular shape of granules from all the species was strikingly similar. Amaranthus polygamous and A. gracilis had low amylose starches (111.7 and 97.1 g kg−1, respectively), and A. spinosus and A. teunifolious had appreciable proportions of amylose (166.7 and 245.0 g kg−1, respectively).

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.

The amylose and lipid contents of starch granules in developing wheat endosperm

Starch was isolated from three varieties of wheat at various stages of grain development (endosperm filling) and separated by sedimentation into eight fractions according to granule size. Starch granule dimensions were measured using a Coulter Counter with 100-Channel analyser, and whole wheat and starch granule compositions were determined. At most stages of development the numbers of Agranules/endosperm remained constant while granule size increased, but the numbers of B-granules/endosperm increased throughout grain development. The amylose content (% dry weight) increased with granule size and with granule maturity, whereas lysophospholipid content (dry weight basis) generally decreased with granule size but increased with granule maturity. Starch deposited on individual large A-granules at successive stages of development contained higher proportions of amylose and lysophospholipids than initial deposits. Similarly, small B-granule starch synthesised at successive stages of grain development contained more amylose and lysophospholipids than the earlier B-granule starch. It was calculated that there should be gradients of amylose and lysophospholipid composition along the outer radii of A-granules, and similar changes in successive populations of B-granules. It is concluded that there was a close relationship between amylose content and lysophospholipid content in the developing A-granules and in the developing B-granules in the starch of each wheat variety, but that this relationship was always different for the A- and B-granules.

A Comparison of the Susceptibility of Two Commercial Grades of Wheat Starch to Enzymic Hydrolysis and their Resultant Oligosaccharide Product Spectra

AbstractSolutions of two commercial fractions of wheat starch, which are separated by their granule size, have been found to differ both in their susceptibility to hydrolysis by α‐amylase and in the oligosaccaride spectra of their resultant hydrolysates. These effects have been ascribed to a reduced proportion of amylose and a higher degree of (1 → 6) branching identified in the starch of the smaller granules.

Changes in the carbohydrate constituents of chickpea and greengram during germination

A decrease in the concentration of total carbohydrates was observed during 96 hours' germination of chickpea and greengram. However, whilst the starch and oligosaccharide levels decreased, the reducing sugars increased. Starch was the major carbohydrate and about 50% of it was hydrolysed after 96 hours' germination. The amylose proportion of the starches increased during germination. Starches from germinated chickpea and greengram had better swelling power and solubility, but their intrinsic viscosity was lower. Changes occurred in the concentration of hemicelluloses during germination but their composition did not alter. The abovementioned changes, occurring during germination, appear to have a favourable effect on the nutritional value of chickpea and greengram.

Galactose-containing polysaccharides from the human pathogens Sporothrix schenckii and Ceratocystis stenoceras.

Galactose-containing polysaccharides from three strains of Sporothrix schenckii and one strain of Ceratocystis stenoceras were isolated, and their structures were paritally characterized by chemical analysis and 13C-nuclear magnetic resonance spectroscopy (13C-NMR). S. schenckii polysaccharide preparations from all strains were not precipitated by Fehling solution and contained galactomannan (or a mixture of galactan and galactomannan), amylose, and minor amounts of rhamnomannan. C. stenoceras polysaccharide contained galactomannan and a smaller proportion of amylose. Conventional chemical techniques and 13C-NMR spectroscopy showed that the structures of the two preparations were closely related. The core of the galactomannan consisted principally of nonreducing end units and 2-O-, 2,6-di-O-, and perhaps 2,3-di-O-substituted alpha-D-mannopyranosyl units. The core was substituted by beta-D-galactofuranosyl chains; the units are interlinked (1 leads to 6). 13C-NMR evidence shows that the alpha-D-mannopyranosyl units are substituted in the two positions by the beta-D-galactofuranosyl residues. Galactomannans present at the cell surface of S. schenckii represent other potential fungal antigens in addition to the already recognized rhamnomannans and their peptide complexes.

Starch-synthesizing Enzymes in the Endosperm and Pollen of Maize

Two mutations, amylose-extender and waxy, which affect the proportion of amylose and amylopectin of starch synthesized in the endosperm of maize (Zea mays L.) seeds, are also expressed in the pollen. However, most mutations that affect starch synthesis in the maize endosperm are not expressed in the pollen. In an attempt to understand the nonconcordance between the endosperm and pollen, extracts of mature pollen grains were assayed for a number of the enzymes possibly implicated in starch synthesis in the endosperm. Sucrose synthetase (sucrose-UDP glucosyl transferase, EC 2.4.1.13) activity was not detectable in either mature or immature pollen grains of nonmutant maize, but both bound and soluble invertase (EC 3.2.1.26) exhibited much greater specific activity (per milligram protein) in pollen extracts than in 22-day-old endosperm extracts. Phosphorylase (EC 2.4.1.1) activity was also higher in pollen than in endosperm extracts. ADP-Glucose pyrophosphorylase (EC 2.7.7.27) activity was much lower in pollen than endosperm extracts, but mutations that drastically reduced ADP-glucose pyrophosphorylase activity in the endosperm (brittle-2 and shrunken-2) did not markedly affect enzymic activity in the pollen. Specific activities of other enzymes implicated in starch synthesis were similar in endosperm and pollen extracts.

The α(1–4)(1–6) glucans from sweet and normal corns

After removal of granular starch at low centrifugal force, the centrifugation, at increasing forces, of aqueous extracts of su 1 corn gave a series of α-glucan precipitates that contained amylose. The amylose content decreased as the force increased. In contrast, in normal corn all the α-glucan precipitated as starch granules at low forces. In the sweet corn precipitates, apart from the granular starch, the branched α-glucan was phytoglycogen. The MW of this decreased as the proportion of amylose decreased. It appears that, as well as starch granules and soluble phytoglycogen, sweet corn contains granules, smaller than starch, of a range of sizes, and these are made up of phytoglycogen and amylose. As granule size decreases, so does the MW of the phytoglycogen and the content of amylose. A method of quantitative extraction of starch giving minimal depolymerization is described. The isopotential iodine absorption of a quantitative extract of sweet corn flour indicated that the total ratio of linear (amylose) fraction to branched (amylopectin + phytoglycogen) fraction was near the normal value of 1:4.

The production of amylose in the faeces of psyllid larvae with special reference to the lerps of Cardiaspina densitexta

The faeces of the larvae of many species of psyllids which feed on the phloem sap of the host plant solidify on contact with the air, and are built by the larvae into characteristic coverings known as lerps. Analysis of the lerps of Cardiaspina densitexta (and a number of other species) by spot testing with iodine, potentiometric iodine titration, precipitation with butanol, the production of spherocrystals of amylose, hydrolysis with sulphuric acid, and paper electrophoresis of the hydrolysis products of lerps, all point to starch—apparently identical to plant starch—being the major constituent of these structures. The relative proportions of amylose in the starch of the lerps of different species varies quite widely. The lerps of C. densitexta contain nothing other than amylose and amylopectin; nitrogen, phosphates, and even ash being absent. In some species other substances may be present in the lerp, and in still others liquid honey-dew containing various soluble sugars is produced as well. The possible selective advantage and evolutionary development of the construction of lerps is discussed.

DEVELOPMENT OF STARCH AND OTHER COMPONENTS IN NORMAL AND HIGH AMYLOSE BARLEY

The rate of synthesis of starch in the North American six-rowed barley Glacier (C.I. 9676) was greater than that in the high amylose cultivar designated Glacier (Pentlandfield). In both cases most of the synthetic activity in the developing grain occurred between the third and sixth weeks after anthesis, but the total starch content of Glacier (Pentlandfield) was reduced by some 6% whilst its total production of protein and fats was greater. The ratio of amylose to amylopectin in the starch of both barleys increased during ripening of the grains, but the proportion of amylose in the mature starch of Glacier (Pentlandfield) attained a value of about 47%, compared with about 26% in Glacier (C.I. 9676). The average diameter of the starch granules in the high amylose barley was smaller than in normal barley at all stages of endosperm development. The two parental varieties and ten others closely related to Glacier were examined, but none possessed the high amylose characteristic.