Characterization of Starch from Maize Endosperm Mutants

Some maize endosperm mutants have branched-chain starch components with long exterior chains which make the blue-value procedure for estimating amylose content questionable. Gel filtration was used to estimate starch composition of normal, high-amylose, waxy and other maize endosperm mutants. Loosely-branched polymers appeared responsible for the apparent amylose content. In some mutants high and intermediate loosely branched polysaccharides were found in addition to amylose. The sweet corn background of some endosperm genotypes influenced the types of polymers produced compared to the dent backgrounds used by previous researchers.     

Studies on Sweet Potatoes. Part II: Isolation and Characterization of Starch

By differential sedimentation and centrifugation steps four starch isolates were recovered from sun dried sweet potato flour. The granules in these isolates were of different size, shape and population characteristics, and were anionic in nature. They showed a single stage swelling with 30 to 35% solubility in water and only ∼30% solubility in DMSO even after 72h. Their starch content varied from ∼48 to 88%. The presence of thermostable amylases in sweet potato resulted in considerable decrease in Brabender viscosity values as amylographic studies in the presence of H_gCl₂ showed significant increase in peak (PV) and setback (SBV) viscosities. The starch isolate I had 25% higher PV as compared to the isolate II but retrogradation was much low in this. Susceptibility to glucoamylase digestion showed a decreasing trend from the isolate I to the IV on solid basis, but comparable on starch basis.     

Developmental Changes in Starch Properties of Several Endosperm Mutants of Maize

The properties of starches during development of several endosperm mutants of maize were investigated. Starch contents of normal and waxy (wx) kernels were higher than those of dull (du), sugary-2 (su₂), and amylose-extender (ae) kernels, and in general the greater increase in starch contents occurred earlier in kernel development. The normal, du, su₂, and ae mutants in that order, respectively, increased the apparent amylose concentration of the starches as measured by the “blue value” method. Within each of these genotypes, absorption intensity increased and λ max. of absorption curves shifted to a longer wavelength region with increasing maturity. Waxy starches did not change in either of these properties at any of the developmental stages. Few detectable differences were observed in X-ray diffraction intensity, gelatinization temperature, heat of gelatinization, and the photopastegrams within these genotypes during development. Exhaustive degradation of starch granules by glucoamylase showed that ae starches were more resistant to amylase than the other starches. Except for wx, the starches tended to be more resistant to amylase with increasing maturity.     

Studies on the Biosynthesis of Starch Granules. Part 7. Compound Granules in Potato Starch

The nature of compound starch granules in potato starch is examined. The relevance of this investigation to the possible formation of potato starch is discussed, and a mechanism for synthesis of compound granules proposed.     

Studies on Rye Starch Properties and Modification. Part I: Composition and Properties of Rye Starch Granules

Rye is considered as a potential raw material for starch industry. Starting from a survey of technical procedures of isolating starches from rye-flour and -grits investigations will be reported, which were performed on pilot plant- and laboratory-isolated rye starches. The present paper deals with its granule appearance and composition. A distribution of granule size between small granules (⩽ 10 μ − 15%) and large granules (⩾ 11 … ⩽ 40 μ − 85%) is typical for the totality of the starches. Differing distributions depend on the conditions of isolation: the entity of starch containing samples resulted from the laboratory procedures under investigation. Large-granule starch preparations were isolated in the pilot plant: the centrifuge-overflow contains the small-granule fraction which is high in impurities. Granule crystallinity amounts to 16%. The crystalline component - like in wheat and triticale starches - consists predominatly of A-polymorph - with up to 9% of the B-type. The isotherms of water exchange are of the cereal type. The contents of minor constituents largely relate to the small granule fraction which assembles the majority of crude protein, pentosans and lipids, which are difficult to remove

1 Large granule samples may be produced in high purity (⩽ 0,2% crude protein)

. Lipid components in all fractions influence the results of linear chain-iodine interactions and they must be removed to proceed from apparent to absolute polysac-charide indices. The absolute amylose contents amount to ∼ 25% for large granule samples and to 20–21% for small granule samples. The average chain-length of iodine binding helical regions was determined with 220–240 AGU.     

Studies on the Biosynthesis of Starch Granules. Part 9. The Starch Granules from Wrinkled-Seeded Peas

The nature of the complex granules of wrinkled-seeded pea starch has been examined, and related to changes in the starch during growth. An earlier hypothesis for the development of pea starch is shown to be untenable in the light of this information, and possible alternative mechanisms for the biogenesis of pea starch are discussed.     

Studies on Rye Starch Properties and Modification. Part II: Swelling and Solubility Behaviour of Rye Starch Granules

Rye starch shows the typical inhibited swelling behaviour of triticeae starches with an onset of swelling at rather low temperature (50–55°C). Swollen rye starch granules exist as individuals even after swelling at 100°C. The total dispersion of rye starch needs temperatures above 120°C with pressure cooking. On heating of the rye starch suspension preferentially amylose is leached. Defatting of rye starch exhibits no influence on swelling power but results in higher solubility and in increased amylose leaching. The drying procedures applied here resulted in stronger assoziation of the polymer molecules in the starch granule leading to higher swelling temperatures and a reduced solubility. Shiftings of the crystalline/ amorphous-ratio of the starch granules as caused by different drying procedures, had no influence on the results of swelling power investigation but the highest swelling enthalpy as well as Brabender viscosity were exhibited by a sample dried at room temperature. It is proved to be possible to change the swelling behaviour of rye starch to “potato starch type” by slight chemical modification like succination.     

The Characterization of Starch and its Components. Part 5. Observations on the Quantitative Acid Hydrolysis of Starch and Glycogen

A method and conditions are presented for the quantitative hydrolysis of starch to glucose by acid, in which no significant levels of acid-catalyzed reversion occur. The relative ease of hydrolysis of the α-1:6-bonds in branched glucans is also investigated.     

A Novel Type of Corn Starch from a Strain of Maize. Part 3. The Properties of the Starch from Amylo-waxy Maize and Its Hybrids with Waxy Maize

A pair of hybrids were produced by alternative crossbreeding of waxy maize with amylo-waxy maize which had double recessive genes, amylose extender (ae) and waxy (wx). Investigation of the starches proved that they did not coincide with waxy starches. Hidden amylose extender genes also participated in the starch produced in the endosperm of hybrid maize. Amylo-waxy starch looks promising as a new material of food industry.     

Components of the Porous Maize Starch Granule Prepared by Amylase Treatment

Porous starch granules were prepared from normal and waxy maize starch with amylase (from Aspergillus sp.) treatment, but we failed to make it from amylostarch under the same condition. The porous normal starch samples of some digestive stage were analyzed to X-ray diffraction, DSC and GPC after debranching process. The X-ray diffraction patterns were changed following with proceed of digestion, but the values obtained from DSC and GPC were not changed. These observations suggest that crystal region may be more sensitive to the amylase than amorphous one, and amylose may be homogeneously distributed in the both regions.     

Studies on the Biosynthesis of Starch Granules. Part 5. Properties of the Starch Components of Normal Barley,and Barley with Sturch of High Amylose-Content,During Growth

Changes in the molecular components of barley starch, from related genotypes of barley differing in amylose-content, have been investigated over the period of reserve-starch deposition in the plants. Striking similarities in the changes in amylose-contents, and in the fine structure of component amylose and amylopectin fractions, were observed over this period, despite the large differences in the types of starch.     

Studies on the Structure of Pea Starches. Part 3: Amylopectin of Smooth Pea Starch

β-Limit dextrins were isolated from smooth pea starch. It was shown by gel chromatography that the sample contained smaller limit dextrins with a degree of polymerization (D.P.) of 40–4000 in addition to high-molecular-weight material. The smooth pea starch and the β-limit dextrins were hydrolysed by the α-amylase of B. amyloliquefaciens and the molecular weight distribution of the reaction mixtures was analysed on Sepharose CL 6B. Initially the reaction was fast, but at later stages branched dextrins with 10–60 were only very slowly hydrolysed further. In addition, linear dextrins with d.p. 2–10 were formed continously. Based on the branched dextrins produced from the β-limit dextrins a model of the structure of the amylopectin component in smooth pea starch is suggested, in which clusters of defined sizes are regularly interconnected.     

Rheological Studies on Potato Starch Pastes at Low Concentrations. Part I. Pasting Characteristics

A novel approach is demonstrated to the determination of pasting characteristics. Using a rotatory viscometer measurements are carried out at constant torque and varying angular speed of rotation. Applied device allows application of low torque, and in consequence studies of starch pastes at low concentrations became available. A model is proposed for characteristics of pastes which involves two parameters independent of measurement conditions.     

The Developing Starch Granule Part I. The Starch Content of Cereal Grains during their Development

When fertilization of developing cereal grains occurs, the pericarp (ovary wall) already contains starch granules. Hence the starch content of developing grains of wheat, triticale, rye, oats and barley commences at 30 or 40% of the dry weight. It increases only to 60 or 70% at ripeness when the pericarp has degenerated to bran layers and the endosperm is filled with stored starch granules and protein. All these cereals showed similar patterns of starch increase, with an inflexion at 40 to 50% starch due to degeneration of pericarp starch before endosperm deposition. In wheats and triticale there was a second inflexion at 50 to 60% starch caused by endosperm cells proliferating faster than they filled with starch granules. The rise and fall of rate of starch deposition coincided with the rise and fall of percentage of metabolic (non-storage) protein in the grain, calculated from total amino acid analyses. In the mature grain about 8% of the dry matter is not associated with starch and thus is non-endosperm tissues. About 70% of the remaining dry matter (endosperm) is starch. We suggest that fluctuations of metabolites and enzymes result from development or breakdown of groups of cells constituting distinct tissues in the grain.     

Studies on Pyrodextrinization of Corn Starch Part II. A Scanning Electron Microscopic Study

A scanning electron microscopic (SEM) study of dextrin prepared in the range of 120°C to 210°C revealed cracks on the surface of some granules and burst granules indicating a gush of hot inner gas and the heat expansion on the surface. And, fused granules appeared in the dextrin prepared at higher temperature (230°C). Furthermore, the damaged granules in the dextrin were determined by rapid differential-staining method with Safranine OK 70: 100 and Direct Sky Blue 5B. The staining affinities of the granules have no relation to cracks, cavities, pin-holes and other physical appearances observed by SEM.     

Studies on the Structure of Pea Starches. Part 2: α-Amylolysis of Granular Wrinkled Pea Starch

Wrinkled pea starch, separated into fractions containing intact granules and fragmented granules together with small intact granules, respectively, was hydrolysed by the α-amylase of Bacillus amyloliquefaciens in a column. The solubilisation rate was similar for both fractions and occurred in three stages: initially increasing, then slowly decreasing, and finally it was very slow. The mixtures of solubilised dextrins had DP (degree of polymerization) 2–100 and their compositions changed as the solubilisation proceeded through the different stages. The products were mostly linear and the composition of the granular residues indicated that amylose preferentially solubilised. Scanning electron microscopy could hardly reveal the site of the attack even though 20% of the granules had been solubilised. It is suggested that the enzyme attacked amylose chains in an amorphous state, whereas chain residues with DP 50–300 remained in the crystalline parts within the granules.     

Studies on Rye Starch Properties and Modification. Part III: Viscograph Pasting Characteristics of Rye Starches

Pasting characteristics of native as well as of physically and chemically modified rye starches have been characterized and compared with the other triticeae starches and starches from maize and potatoes. Normal and pressure viscograph techniques were applied. Additional, ridgelimetry investigation were performed with the gels formed from the viscographically prepared pastes. Rye as well as wheat and triticale starches exhibit unique, typical gelatinization behaviour, late onset of consistency gain, low but highly stable cooking consistency, consistency gain of the two-threefold on cooling. Gels are of statistically lower firmness as those of maize starch. Higher degrees of consitency, good cooking stability and high consistency gain on cooling were achieved after treatment in the pressure viscograph (max. temp. 120°C). Physical treatment like annealing, heat-moisture treatment, extraction by aqueous solvents, drying procedures result in different but in each case typical change of properties: shift of onset consistency gain, lower maximum consistency values, lower consistency gain on cooling. Gelfirmness will be enhanced in every case. The pasting characteristics of heat-moisture treated wheat starch differ from this by remarkably higher consistency values. Possible reasons for this are discussed. Succination (0.7-2.1%) changes the pasting characteristics towards the potato starch type, lower onset temperatures of consistency gain, very high values in maximum consistency, diminished cooking stability. The gels formed are smooth and turbid. Acetylation (0.7-2.3%) changes the pasting characteristics towards the maize starch type, maximum consistencies are lower compared with succinated triticeae starches. Ac contents of 0.7% inhibit the formation of rigid gels.