Absence Of Amylose Research Articles

On the Architecture of Starch Granules Revealed by Iodine Binding and Lintnerization. Part 2: Molecular Structure of Lintnerized Starches.

This investigation validated iodine binding in combination with lintnerization for studying the structural nature of the amorphous areas in starch granules. Lintners of four iodine vapor-stained and non-stained amylose-containing starches and their waxy counterparts were analyzed by high-performance anion-exchange chromatography (HPAEC). The composition of the lintners was strongly affected by the absence of amylose in barley and potato starch but not in maize and cassava starch. Iodine-stained waxy lintners possessed increased number of long B2 chains. β-Limit dextrins of the lintners were very variable in composition. Iodine inclusion complexes washed out from the granular residues in the lintners (mostly from amylose-containing barley and maize starches) were also analyzed. Acid-soluble complexes from both amylose-containing and waxy starches possessed a lot of material with a degree of polymerization (DP) around 60 and a periodicity in size of DP 8-12. Such long chains were only minor components in water-soluble complexes of amylose-containing barley and maize starch lintners, and they lacked the size periodicity. Models of the principal structure of the acid and water-soluble complexes are suggested. It is concluded that acid hydrolysis of iodine-stained starch granules is a useful tool in structural analyses of the molecular composition of amorphous parts of starch granules.

Native and fermented waxy cassava starch as a novel gluten-free and clean label ingredient for baking and expanded product development.

Amylose-free and wild-type cassava starches were fermented for up to 30 days and oven- or sun-dried. The specific volume (ν) after baking was measured in native and fermented starches. The average ν (across treatments) for waxy starch was 3.5 times higher than that in wild-type starches (17.6 vs. 4.8 cm3 g-1). The best wild-type starch (obtained after fermentation and sun-drying) had considerably poorer breadmaking potential than native waxy cassava (8.4 vs. 16.4 cm3 g-1, respectively). The best results were generally obtained through the synergistic combination of fermentation (for about 10-14 days) and sun-drying. Fermentation reduced viscosities and the weight average molar mass led to denser macromolecules and increased branching degree, which are linked to a high loaf volume. The absence of amylose, however, was shown to be a main determinant as well. Native waxy starch (neutral in taste, gluten-free, and considerably less expensive than the current alternatives to cassava) could become a new ingredient for the formulation of clean label-baked or fried expanded products.

Effect of hydrocolloids on waxy maize starch and its distarch phosphates

Native and cross-linked waxy maize starch (WMS) were heated in water or one of 9 hydrocolloid (HC) solutions. Results indicated that HC affected pasting of the starch and that the various HC interacted to different degrees with native WMS granules (controlling their swelling and disintegration). After comparing the results to those for normal maize starch (NMS), it was concluded that most HC acted on both WMS and NMS, only in different ways and to different degrees, and that the presence or absence of amylose was probably involved in creating the differences, but that might not be the entire reason. Results also indicated that native WMS, less cross-linked WMS, and more cross-linked WMS each behaved in a distinct way when a HC was added and that most HC effected an increase in granule strengthening with cross-linked NMS being strengthened more than cross-linked WMS. A hypothesis for the effects of HC on granule swelling and pasting is presented. It is also acknowledged that attributes imparted by the HC itself may impact paste rheology.

Impact of annealing on the hierarchical structure and physicochemical properties of waxy starches of different botanical origins

The effect of annealing on structure and physicochemical properties of four different waxy starches were investigated to understand the mechanism of annealing in the absence of amylose. Granule morphology, X-ray pattern, molecular order, and gelatinization enthalpy remained unchanged upon annealing. Relative crystallinity of waxy corn starch increased from 42.4 to 46.1% on annealing, while it remained unchanged in other starches. Annealing increased the gelatinization temperatures, while it decreased the temperature range. Waxy potato starch showed the highest increase in To, where it was 8.1 °C after 72 h of annealing. Viscosity profiles were only slightly affected by the annealing treatment. Susceptibility towards amylolysis increased in waxy corn and waxy barley, while it decreased in waxy potato and waxy rice. This study demonstrated that even in the absence of amylose, annealing caused changes in the structure and properties, however, the extents of these changes varied depending on the botanical origin.

Occurrence of the Waxy Alleles wxa and wxb in Waxy Sorghum Plant Introductions and Their Effect on Starch Thermal Properties

The existence of two waxy alleles, wxa associated with no detectable granule bound starch synthase (GBSS) and wxb associated with apparently inactive GBSS, was recently reported in sorghum [Sorghum bicolor (L.) Moench]. In this paper, the occurrence of the wxa and wxb alleles in the USDA‐ARS photoperiod‐insensitive sorghum collection was determined, and the effects of the wxa and wxb alleles on thermal properties of sorghum starch (gelatinization temperatures and energy requirements) measured by differential scanning calorimetry. Of the 51 purported waxy accessions examined, 14 tested positive for presence of amylose by iodine staining and were considered to be previously misclassified wild‐type lines. Nine accessions were mixed for presence or absence of amylose. Twenty‐four of the 28 accessions confirmed to be waxy by negative iodine staining for amylose had no detectable GBSS using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE) (wxa), and four were show to contain GBSS (wxb). Mean gelatinization onset, peak, and end temperatures were significantly lower for wild‐type than either of the two waxy genotypes. Mean gelatinization onset temperature was slightly higher for waxy‐GBSS+ genotypes than waxy‐GBSS− genotypes. Mean gelatinization end temperature was slightly higher for waxy‐GBSS− genotypes than waxy‐GBSS+ genotypes. Significant genetic variation was observed within genotypic classes, suggesting influence of additional modifier genes affecting sorghum starch structure or micro‐environmental effects.

Discovery of an Amylose-free Starch Mutant in Cassava (Manihot esculenta Crantz)

One of the objectives of the cassava-breeding project at CIAT is the identification of clones with special root quality characteristics. A large number of self-pollinations have been made in search of useful recessive traits. During 2006 harvests an S1 plant produced roots that stained brownish-red when treated with an iodine solution, suggesting that it had lower-than-normal levels of amylose in its starch. Colorimetric and DSC measurements indicated low levels (3.4%) and an absence of amylose in the starch, respectively. SDS-PAGE demonstrated the absence of GBSS enzyme in the starch from these roots. Pasting behavior was analyzed with a rapid visco-analyzer and resulted in larger values for peak viscosity, gel breakdown, and setback in the mutant compared with normal cassava starch. Solubility was considerably reduced, while the swelling index and volume fraction of the dispersed phase were higher in the mutant. No change in starch granule size or shape was observed. This is the first report of a natural mutation in cassava that drastically reduces amylose content in root starch.

Physico-chemical Characterization of Floridean Starch of Red Algae

The current work reports on isolation and physico-chemical characterization of floridean starch from three species of agarophytic macro red algae. As determined by 1H-NMR spectroscopy, the average chain length and degree of branching frequency of this starch were 18 and 4.8, respectively. According to its amylopectin chain length distribution obtained by Dionex analysis, the crystalline polymorph of floridean starch from the red alga Gracilariopsis lemaneiformis was deduced to be C-type and this was further supported from its X-ray crystallographic pattern. Enzymatic analysis of its glucose 6-phosphate content showed that floridean starch had a low level of covalently linked phosphate (1 nmol per milligram starch) and this was further confirmed by 31P-NMR. The absorbance peak of floridean starch with iodine occurred at 527—530 nm and the blue value was low (0.1), indicating the absence of amylose, which was confirmed by differential scanning calorimetry (DSC). Floridean starch exhibited low gelatinization temperature, low viscosity, high clarity and little or no retrogradation upon repetitive freeze-thaw cycles, as studied by DSC and rapid viscosity analysis (RVA). These results are discussed in light of the functional properties and the structure of floridean starch.

Localisation of Amylose and Amylopectin in Starch Granules Using Enzyme-Gold Labelling

The independent localisation of amylose and amylopectin in a range of dry and hydrated native starch granules with varying amylose content (0—70 %) has been indirectly visualised using enzyme-gold cytochemical markers. Increasing amylose content was clearly demonstrated to result in distinct changes in granule architecture. In the absence of amylose (waxy maize starch) a framework of closely packed concentric layers of amylopectin exists in the granules. Low amylose content (potato starch) results in alternating layers of densely packed amylopectin and amylose molecules. High amylose content (amylomaize starch) granules were shown to possess an amylopectin centre surrounded by an amylose periphery encapsulated by an amylopectin surface. Elongated granules without the amylopectin centre were also observed in high amylose starches suggesting a relationship between amylopectin, amylose and granule shape. A model of starch granule architecture is proposed where increased compartmentalisation of amylose and amylopectin is observed in granules containing increasing levels of amylose.

The influence of an increased degree of branching on the physico-chemical properties of starch from genetically modified potato

Transgenic potatoes were studied which contained starch with an increased degree of branching of the starch as a result of the expression of the glycogen branching enzyme gene (glgB) of Anacystis nidulans or Escherichia coli. These trans-genes were expressed in a normal amylose-containing wildtype and in an amylose-free (amf) potato mutant. The degree of branching of these starches had increased up to 25%. This increase in the degree of branching could be partly explained by the presence of 5–15% more short chains in the amylopectin, the so-called A chains. The influence of the altered degree of branching on the physico-chemical properties of the starches was investigated. No change in granule size or morphology could be observed for the altered starches of these transgenic plants. Regardless of the presence or absence of amylose, starches with an increased degree of branching showed a shift towards more short chains of the amylopectin, a lower peak viscosity and for the amylose-free starch a tendency to form weaker gels. These results show that increasing the degree of branching of amylopectin leads to specific changes in the physico-chemical properties of the starch.

The dosage effect of the wildtype GBSS allele is linear for GBSS activity but not for amylose content: absence of amylose has a distinct influence on the physico-chemical properties of starch

The dosage effect of the wildtype GBSS allele is linear for GBSS activity but not for amylose content: absence of amylose has a distinct influence on the physico-chemical properties of starch

The dosage effect of the wildtype GBSS allele is linear for GBSS activity but not for amylose content: absence of amylose has a distinct influence on the physico-chemical properties of starch

A gene-dosage population was obtained by crossing two genotypes that were duplex for the GBSS allele. Nulliplex, simplex, duplex or triplex/quadruplex plants could be identified by monitoring the segregation of red and blue microspores after staining with iodine. GBSS activity was significantly different for all groups and showed an almost linear dosage effect for the wildtype GBSS gene. A dosage effect was found for amylose content that was not linear. The amylose content was similar for both the duplex and triplex/quadruplex group. Within the simplex group, differences in amylose content were found, which might be due to a different genetic background. There was no linear correlation between GBSS activity and amylose content. A certain level of GBSS activity led to a maximum amount of amylose, and further increase in GBSS activity did not result in a further increase in amylose content. The presence of one or more wildtype GBSS allele(s), and therefore the presence of amylose in the starch granules, had a great influence on the physico-chemical properties of the starch suspensions.

A spectroscopic study of amylose-rose bengal complexes

Amylose interacts strongly with lipids, fatty acids, dyes, and many low molecular weight molecules’-5, and forms helical inclusion (V-amylose) complexes with the guests accommodated within the amylose helix6q7. The complexes involve mainly hydrophobic interactions**‘, and are stabilised by intramolecular hydrogen bonding”. The ability of amylose to form complexes is connected mainly with the conformation of the molecule and is correlated with the orientation of the functional groups in monomeric unitss*“-‘3. In exploring the conformational properties of amylose and its interaction with dyes, we have studied, and now report on, amylose-Rose Bengal complexes in aqueous solutions as a model system. The changes in the u.v.-visible absorption spectrum of 1.5 x 10~“M Rose Bengal in the presence of various concentrations of amylose are shown in Fig. 1. The rl,,, at 545 nm in the absence of amylose is shifted to 559 nm when 8% of amylose is present and the intensity decreases by 25%. There is a linear dependence of the shift in frequency and the decrease in intensity only up to 4% of amylose. Above 4%) there is little effect on either parameter (saturation effect). Likewise, the shoulder at 507 nm is shifted to 520 nm when 8% of amylose is present, but the intensity does not change. Rose Bengal is an efficient photosensitiser and appropriate precautions are necessary. The absorption spectrum shows up an isosbestic point at 556 nm, which reflects the equilibrium between the dye in solution and that on the surface or within the amylose helix, where the environment is more hydrophobic and causes the shift of A,, towards longer wavelength. The difference between the nominal concentration and that in the presence of amylose corresponds to the proportion of the dye in the complex, and the mono-anionic form of the dye is assumed to be responsible for all observed changes in absorption spectrum.

Photochemical reactions in organized assemblies. 40. Amylose and carboxymethylamylose inclusion complexes with photoreactive molecules

This paper focuses on a study of unimolecular and bimolecular photoreactions occurring with reactants which can be incorporated into the linear polysugars amylose and carboxymethylamylose. Hydrophobic and surfactant trans (E) stilbene derivatives form complexes in which the stilbene chromophore shows enhanced fluorescence and reduced trans → cis isomerization efficiencies. The reactivity of the excited surfactant–stilbene singlet towards the quencher iodide ion has been compared in water/dimethylsulfoxide in the presence and absence of amylose under conditions where complex formation is nearly complete. Some relatively hydrophobic viologen dications have also been found to form complexes with the water soluble carboxymethylamylose. Although the dications complex relatively weakly, the partially reduced monocations complex more strongly. This results in selective retardation of back electron transfer rates when the viologens are used as electron transfer quencher-oxidants for certain luminescent ruthenium polypyridine complexes.