Properties of Starches Isolated from Sorghum Floury and Corneous Endosperm

Decorticated grains of three sorghum cultivars of intermediate grain hardness were individually dissected to separate the floury and the corneous endosperm fractions. The starch and polymeric components (amylose and amylopectin) of each of the endosperm fractions were isolated and subsequently characterized. Results indicate that there exist major differences in the properties (granule size distribution, gelatinization temperature, iodine binding capacity, and rate of lintnerization) of the starch and starch components from the endosperm fractions. Close relationships between the starch properties and the strength of the alkali gel of the corresponding endosperm fraction were observed.     

Chain‐length Distribution Profiles of Amylopectin Isolated from Endosperm Starch of Waxy and Low‐amylose Bread Wheat (Triticum aestivum L.) Lines with Common Genetic Background

Large A‐type endosperm starch granules were isolated from near‐isogenic waxy and non‐waxy lines and low‐amylose mutant lines of bread wheat with a common genetic background. The amylose contents of A‐type starch ranged from 2.6% to 23.6%. Amylopectin was isolated by concanavalin A (Con A) precipitation from the isolated starch. The λ_max (range: 532‐538 nm) and blue values at 680 nm (range: 0.026‐0.037) of the iodine‐amylopectin complex were not significantly different among the isolated amylopectins, indicating that amylopectins from non‐waxy and low‐amylose lines did not contain such long chains as amylose or extra‐long chains of amylopectin affecting iodine complex properties. Chain‐length distribution profiles measured by both high‐performance size‐exclusion chromatography (HPSEC) and high‐performance anion‐exchange chromatography (HPAEC) showed that the amylopectin structures of these lines were indistinguishable from each other. Extra‐long chains were not detected in the amylopectins by HPSEC measurement. The side‐chains measured by HPAEC were classified into four groups according to their degree of polymerization (DP), and the proportion of each group were in the following ranges: DP 6‐12, 26.5‐27.5%; DP 13‐24, 43.6‐44.1%; DP 25‐36, 13.6‐14.2%, and DP 37‐60, 11.0‐11.7%. The alleles on the Wx‐D1 locus, i.e., Wx‐D1a, Wx‐D1d, Wx‐D1f, and Wx‐D1g, responsible for granule‐bound starch synthase (GBSS I) biosynthesis had no influence on the properties of iodine‐amylopectin complex and the chain‐length distribution profiles of amylopectin.     

Structure and Physicochemical Properties of Endosperm Starches of a Waxy Allelic Series and Their Respective Normal Counterparts in the Inbred Oh43 Maize Background

Research over the past three decades has greatly increased our understanding of the biochemical genetics of various waxy (wx) alleles of maize, but our knowledge about the structure and physicochemical properties of endosperm starches obtained from the wx alleles is still incomplete. We further investigated the structure and physicochemical properties of endosperm starches from a wx allelic series and their normal counterparts in the Oh43 inbred background. Starch granules were prepared from mature kernels of wx mutant alleles; wx-C31, wx-R, wx-90, wx-a, wx-B3, wx-m-1, wx-m-8, and wx-S5, and their respective normal counterparts in the inbred Oh43 maize background. Measurements of absorption spectra of starch-iodine complexes and by gel permeation chromatography of Pseudomonasisoamylase-debranched starches showed that all of the starches from the wx allelic series were uniquely waxy type in characteristics, and their normal counterparts were characteristically normal type. Pasting characteristics of starch granules and retrograded starches of the wx allelic series and their respective normal counterparts were investigated by differential scanning calorimetry (DSC). The peak temperature (Tp) and conclusion temperature (Tc) values from starches of the wx allelic series were slightly higher than those of their respective normal counterparts and the ΔHs of starches of the wx allelic series were greater than those of their respective normal counterparts. The onset temperature (To), Tp, and Tc of all retrograded starches were very similar, however, the ΔHs of the retrograded starches of the wx allelic series were greate than those of their respective normal counterpart. Starch granules of the wx allelic series were hydrolyzed more rapidly than those of their respective normal counterparts.     

Properties of Starches from Australian Wheats. Part 2: Some Physico-chemical Properties

Various physico-chemical properties of starches isolated from 21 Australian wheat varieties were assessed. Molecular weights varied between the starches and were lower in those from soft wheats. Proportions of small granules were significantly correlated with starch amylose and protein contents; those of large granules correlated negatively with fat content. Granule crystallinity was correlated with hardness of the parent wheats. Gelatinisation temperatures, measured by differential scanning calorimetry, varied between the starches within the range of 46–79°C. Enthalpies of gelatinisation, 4.6–13.3 J/g of dry starch, were correlated with both amylopectin content and wheat hardness. Minimum moisture for gelatinisation, 0.15–0.56 wa-ter/g of dry starch, was significantly correlated with both amylose and fat contents of the starch.     

Physicochemical Studies on Starches. Part 63. The Molecular Size and Shape of Amylopectin

Light-scattering, viscosity and ultracentrifugal techniques have been applied to a number of amylopectin samples. These measurements have confirmed the very large size of the macromolecule, and shown that such values are real, and are not due to aggregation resulting from hydrogen-bonding. The hydrodynamic behaviour of amylopectin has been compared with that of the closely-related glycogen. The difference between the two has been shown to be due to the much more flexible, coil-like nature of the amylopectin. An examination has been made of the factors governing the extension of amylopectin as the pH is varied, and it is shown that under appropriate solvent conditions a “coil-to-helix” transformation may be observed. The conformation of the amylopectin molecule is discussed, and the concept that the macromolecule is a two-dimensional entity is proposed.     

Gamma Radiolysis of Starches Derived from Different Foodstuffs. Part IV. Study of Radiodepolymerization

The foodstuffs from which the investigated starches (maize, waxymaize, amylomaize, manioc, bread-wheat, potatoe, rice and haricot bean) derive has only little influence upon their radiodepolymerization, as previously stated by theory.     

Properties of Starches from Australian Wheats. Part 1: Separation of Starch and Gluten

Starch and gluten were isolated from flours milled from 21 Australian wheat varieties. Relative yields of starch and gluten varied in general accord with flour protein content. Recoveries of total solids (starch plus gluten) ranged from 67.6% to 85.1% amongst the varieties. Significant differences in proximate composition and amylose content were observed between the isolated starches. This was especially so for starch protein content which was significantly correlated with wheat hardness. Potential benefits exist for the starch/gluten industry in selecting wheats on the basis of minimal loss of total solids during the process, and for purity and amylose content of the isolated starch.     

Studies on Sago Starch. Part I: Characterization and Comparison of Sago Starches Obtained from Metroxylon sagu Processed at Different Times

This paper reports on a study undertaken to determine some of the factors responsible for the variability shown by sago starch, which at present severely limits the commercial value of this material. Two batches of sago starch extracted from Metroxylon sagu species were characterized physicochemically and structurally. One batch was white in colour while the other was reddish-brown. The latter contained significantly more protein (0.06%) than the former (0.015%). Non-proteinaceous material constituted 40% of the total nitrogen in the former. The ionic contents of the two batches of starch exhibited a similar ion profile except for the following striking differences. The white batch contained 20-fold more phosphorus and 15-fold more aluminium whilst the reddish-brown batch contained double the quantity of iron and calcium. The solubility and swelling capacity of both batches were also different. Amylographic representation was used to reveal the strength of starch granules during pasting. Scanning electron microscopy disclosed different degrees of pitting between the two batches, the morphology of which were also shown to be disparate. Flow curves also displayed significant differences in the rheological behaviour.     

Properties of Starches from Australian Wheats. Part 3: In vitro Digestibility and Hydroxypropyl Derivatives

The in vitro digestibilities of starches isolated from 21 Australian wheat varieties were measured after gelatinisation, using porcine pancreatic α-amylase. The starches were also converted into their hydroxypropyl derivatives and levels of substitution, and freeze-thaw stability of the products assessed. Digestibilities varied between samples and were significantly correlated negatively with fat content of the starches. No significant correlations between digestibilities and any of amylose content, grain hardness or granule crystallinity were found. Efficiency of reagent usage during derivatisation and freeze-thaw stability also varied between starches. Levels of substitution were not reflected in relative freeze-thaw stabilities of the starch derivatives.     

Xerophytic Cucurbit Root Starches. Part VI: Preliminary Investigation of Starches from Apodanthera undulata Gray,Marah gilensis Greene and Maximowiczia lindheimeri Gray

The root starches of Apodanthera undulata Gray, Marah gilensis Greene and Maximowiczia lindheimeri Gray were quantified, isolated and characterized to expand knowledge concerning potentially useful products from xerophytes. Apodanthera roots contained relatively high levels of starch (20.5%) whereas starch levels in the other two species were 8.2 and 9.5%, resp. Starch isolated from Apodanthera manifested physical, physico-chemical and rheologic properties which closely resembled those of the potentially commercial Cucurbita foetidissima and Cucurbita digitata root starches. Granules were composed of approximately 26% amylose, were of medium size, were round, oval, or truncated in shape; and were moderately resistant to gelatinization, swelling and solubilization. Suspensions displayed high initial pasting temperatures. The pastes were resistant to collapse and developed only a modest level of set-back upon cooling. Starch from Maximowiczia also resembled Cucurbita starches for most parameters but exhibited a higher resistance to granule hydration and disintegration than any of its counterparts. Granules of Marah starch were somewhat larger than those of other starches within this group and their equilibrium moistures were high. They offered little resistance to gelatinization, were more free-swelling and soluble than other subject materials, and in suspension they displayed a relatively low initial pasting temperature. Furthermore, Marah pastes were more highly viscous than those of other subject materials during the pasting cycle and suffered regain as they cooled.     

Variation in the Chain‐length Distribution Profiles of Endosperm Starch from Triticum and Aegilops Species

The baseline variation data on the chain‐length distribution profiles of endosperm starch were acquired for use as a criterion for variation among bread wheat (Triticum aestivum L.) cultivars/lines. A total of 126 starch samples isolated from closely related species belonging to the Triticum‐Aegilops group, i.e., five Triticum and 22 Aegilops species, were examined. Their side‐chains were debranched by isoamylase and chain‐length distribution profiles were determined by high‐performance anion exchange chromatography with pulsed amperometric detection (HPAEC‐PAD). An averaged chain‐length distribution profile calculated from all data indicated that the most abundant side‐chain had a degree of polymerization (DP) of 11 and its proportion based on relative peak area was 7.5%. The side‐chains were classified into four groups, and the average proportions of each group were as follows; DP 6–12, 28.5% (range 26.3–30.9%); DP 13–24, 48.6% (46.2–50.8%); DP 25–36, 13.7% (12.8–15.2%) and DP ≥37, 8.9% (7.2–10.6%). The chain‐length distribution profiles of Triticum and Aegilops species were essentially similar and no peculiar profile was observed. The range of the variation in the proportion of side‐chain groups, however, was comparable to the difference between waxy and non‐waxy bread wheat starches and among starches from wheat grown at different temperatures; this would affect the gelatinization and retrogradation properties of starch.     

Studies on Starches of High Amylose-Content. Part 14. The Fractionation of Amylomaize Starch by Aqueous Leaching

Amylomaize starch is known to contain an anomalous material which does not conform to the classical definitions of either amylose or amylopectin. A detailed study of this polysaccharide has not yet been carried out, principally because of the difficulty of obtaining it in sufficient quantity. This paper presents a rapid and simple method by which the isolation may be achieved.     

Chemical Structure of Barley Starches. I. A Study of the Properties of the Amylose and Amylopectin from Barley Starches Showing a wide Variation in Brabender Cooking Viscosity Curves

The starches from two barley varieties showing extreme differences in cooking viscosity were fractionated. The amylose and amylopectin from the variety showing a high cooking viscosity, Nupana, are larger than those from the low cooking viscosity variety, Titan. Although no substantial differences were observed in the yields and chain length in the debranched amylopectins, there is evidence that the Titan amylopectin branches contain a block to β-amylase action. This would account for the low beta-limit on the Titan amylopectin. The breaking of H-bonding on heating should allow the starch fractions more freedom to expand and accounts for the fact that the starch having the largest fractions exhibits the greatest viscosity. The molecular size of amylose as estimated by the use of the polarograph suggests that the use of limiting viscosity for this purpose should be used with caution.     

Polymer-Water Interaction of Maltodextrins. Part I: Water Vapour Sorption and Desorption of Maltodextrin Powders

Polymer-water interactions of a low DE maltodextrin and its P _n fractions are investigated by water vapour sorption and desorption measurements. The interpretation of the isotherms was done by the application of the three parameter Guggenheim-Anderson-de Boer equation and by the Flory-Huggins theory. The polymer-water interactions of the maltodextrin and its fractions exhibit strong dependence on P _n. The monolayer water content, the water uptake up to a_w 0.95, the hysteresis effect, the water content of the transition powder-gel under sorption conditions and the ability to form gels decrease with decreasing P _n. The water uptake above a_w 0.95, the monolayer sorption enthalpy and solubility increase with decreasing P _n. The participation of molecular different fractions of the maltodextrin in polymer-water interaction depends on the polymer concentration. Shelf live conditions for the maltodextrin are derived.     

Varietal Differences in Surface Ultrastructure of Endosperm Cells and Starch Granules of Rice

A study was made of varietal differences in surface ultrastructure of endosperm cells and native and modified starch granules of rices. Scanning electron microscopy of the fracture face of the endosperm verified that opacity in nonwaxy rice was due to the loose arrangement of cell contents. By contrast, the endosperm of waxy rice only showed a mealy portion although it is opaque. Corrosion with HCl resulted in little change in surface structure, whereas α-amylolysis resulted in varietal differences in corrosion patterns. Waxy granules showed the fastest and most uniform pitting on α-amylolysis.     

Structure and Properties of Endosperm Starch and Water Soluble Polysaccharides from Sugary Mutant of Rice (Oryza sativa L.)

Structure and properties of starch and water soluble polysaccharides (WSP) from sugary (su) endosperm of rice were examined. The su starch contained more amylose and had a somewhat higher ratio of the short chains to the long chains of amylopectin than normal starch. The WSP consisted of short α-1, 4-chains and their average degree of polymerization was 8.6 glucose units. Susceptibility of the su starch to crude Rh. glucoamylase was higher than that of the normal. The initial and final temperatures and heat of gelatinization of the su starch granules were much lower than those of the normal ones.