Crystalline Structure Of Starch Research Articles

Radiation grafting of styrene on starch with high efficiency

Wheat starch grafted with polystyrene (PS-g-starch) was synthesized via polymerization grafting of styrene on starch by gamma-ray. The effects of starch/styrene weight ratio, and amount of applied doses (5–40kGy) on the percentage of grafting, G (%), were investigated. The results showed that G (%) increased with increasing starch content. The optimum condition, starch/styrene weight ratio 1/3 and the applied dose 10kGy, led to 252.9% of grafting. The obtained graft copolymer was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermal gravimetric analysis, and scanning electron microscopy. FTIR spectroscopy as well as the XRD analysis exhibited the changes in chemical and crystalline structure of starch after grafting reaction. TGA demonstrated the changes in thermal stability of PS-g-starch copolymer. SEM micrographs indicated porous patches of PS adhering on the starch.

Structural Changes of Starch during Baking and Staling of Rye Bread

Rye sourdough breads go stale more slowly than wheat breads. To understand the peculiarities of bread staling, rye sourdough bread, wheat bread, and a number of starches were studied using wide-angle X-ray diffraction, nuclear magnetic resonance ((13)C CP MAS NMR, (1)H NMR, (31)P NMR), polarized light microscopy, rheological methods, microcalorimetry, and measurement of water activity. The degree of crystallinity of starch in breads decreased with hydration and baking to 3% and increased during 11 days of storage to 21% in rye sourdough bread and to 26% in wheat bread. (13)C NMR spectra show that the chemical structures of rye and wheat amylopectin and amylose contents are very similar; differences were found in the starch phospholipid fraction characterized by (31)P NMR. The (13)C CP MAS NMR spectra demonstrate that starch in rye sourdough breads crystallize in different forms than in wheat bread. It is proposed that different proportions of water incorporation into the crystalline structure of starch during staling and changes in starch fine structure cause the different rates of staling of rye and wheat bread.

Graft Copolymerization of Acrylamide onto Activated Starch Using Inverse Emulsion Polymerization

Activated starch was prepared by ball milling before used. Graft copolymerization of acrylamide onto activated starch was carried out in inverse emulsion using a redox initiation system of ammonium persulfate and sodium bisulfite. The effects of ball-milling time, reaction temperature, initiator concentration and weight ratio of acrylamide to starch on the conversion of monomer, grafting percentage and grafting efficiency were studied. The structure and properties of the graft copolymer and activated starch were characterized by FT-IR, XRD and SEM. The results showed that ball milling could progressively destroy the crystalline structure of starch and improve the chemical reactivity. The monomer conversion, grafting percentage and grafting efficiency of grate copolymerization were 96.6%、62.4%、85.49%, respectively.

C-Type Starch from High-Amylose Rice Resistant Starch Granules Modified by Antisense RNA Inhibition of Starch Branching Enzyme

High-amylose starch is a source of resistant starch (RS) which has a great benefit on human health. A transgenic rice line (TRS) enriched amylose and RS had been developed by antisense RNA inhibition of starch branching enzymes. In this study, the native starch granules were isolated from TRS grains as well as the wild type, and their crystalline type was carefully investigated before and after acid hydrolysis. In high-amylose TRS rice, the C-type starch, which might result from the combination of both A-type and B-type starch, was observed and subsequently confirmed by multiple physical techniques, including X-ray powder diffraction, solid-state nuclear magnetic resonance, and Fourier transform infrared. Moreover, the change of starch crystalline structure from C- to B-type during acid hydrolysis was also observed in this RS-rich rice. These data could add to our understanding of not only the polymorph structure of cereal starch but also why high-amylose starch is more resistant to digestion.

Genetic Effect of PUL Allelic Variation on Rice Cooking and Eating Qualities

Pullulanase (PUL) is a type of starch debranching enzymes involved in starch biosynthesis. To test the effect of PUL allelic variation on cooking and eating qualities in rice ( Oryza sativa L.), 2 sets of near-isogenic lines (NILs) for PUL gene were developed by crossing and backcrossing Guichao 2 ( indica) and Suyunuo ( japonica glutinous) and selected with the help of the gene-specific STS marker on PUL gene. The NILs had no significant differences in amylose content, gel consistency, and starch crystalline structure compared with their corresponding recurrent parents. In contrast, the starch paste viscosity and starch thermal property changed obviously between the NILs and their recurrent parents. It was concluded that PUL gene plays an important role in determining rice grain cooking and eating qualities, and functional differentiation occurred at the PUL locus between indica variety Guichao 2 and japonica variety Suyunuo. The gene-specific molecular marker for PUL gene developed on the basis of genomic sequence diversity could be directly applied in rice good quality breeding program.

Synthesis of cationic starch with a high degree of substitution in an ionic liquid

Abstract Cationic corn starch derivatives containing quaternary ammonium groups with a high degree of substitution were synthesized by reacting corn starch with glycidyltrimethylammonium chloride (GTAC) in a homogeneous manner using 1-butyl-3-methylimidazolium chloride (BMIMCl) as a reaction medium. The influence of reaction time, reaction temperature, the amount of catalyst NaOH and molar ratio of GTAC/anhydroglucose units in starch on the degree of substitution (DS) of products was investigated. The maximum DS value obtained in the optimum reaction condition was up to 0.99. Furthermore, the structure of cationic starch derivatives was characterized by means of Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), X-ray powder diffraction (XRD), thermal analysis and 1 H NMR spectroscopy. The results showed that the ordered crystalline structure of native starch was largely destroyed during the dissolution and functionalization of starch in the ionic liquid BMIMCl, leading to an uniform etherification reaction to be carried out under the homogeneous reaction conditions.

Convenient method for preparation of hydrophobically modified starch nanocrystals with using fatty acids

Biodegradable nanoparticles of starch were prepared by an acid treatment process. The obtained starch nanoparticles were hydrophobically modified by using octanoyl, nonanoyl and decanoyl chloride in the aqueous media under mild condition. The structure of the resulted polymers characterized with FT-IR spectroscopy and DS-values calculated by elemental analysis experiment. Thermal characteristic of the modified starch nanoparticles was investigated using TGA technique. By introducing fatty acids, onset temperature for modified starch nanoparticles has increased and starch nanoparticles showed greater thermal stability. Also wettability tests showed that the surface characters of starch nanocrystals have changed during modification and modified starch nanocrystals have higher affinity toward organic solvents rather than aqueous media. DSC studies showed that the starch crystalline structure has not changed during reaction.

Morphology and physicochemical properties of mechanically activated rice starch

The morphology and physicochemical properties of mechanically activated rice starch (MARS) isolated from three rice cultivars were investigated by scanning electron microscopy, X-ray diffractometry, gel permeation chromatography and Rapid Visco Analysis. The shape of rice starch granule changed from native polyhedron to anomalistic state during mechanical activation. It was suggested that the hydration of starch and moisture was an important factor for granules agglomeration which appeared more easily with higher moisture content. Mechanical force resulted in destroying of starch crystal structure which disappeared basically after activated for 10h. As the mechanical activation time prolonged, the amylopectin and amylose of rice starch were both decomposed gradually, thus causing the increase of cold-water solubility and reducing power and the decrease of BV. Meanwhile, the pasting temperature and the viscosity of MARS decreased, including peak viscosity, final viscosity, breakdown viscosity and setback viscosity. The crystalline and molecular structure of rice starch with 6.02% moisture content were more easily destroyed by mechanical force than those with 1.05% and 11.05% moisture content, which resulted in higher cold-water solubility and reducing power, lower BV, pasting temperature, peak viscosity, final viscosity, breakdown viscosity and setback viscosity.

Extrusion and Characterization of Starch Films

ABSTRACTStarch plasticized with water, glycerol, and stearic acid was extruded and sheeted into films 0.4–0.6 mm thick. The ingredients were extruded in a conical twin‐screw extruder at a temperature profile of 50–120–120–120°C and a screw speed of 45 rpm. The effects of glycerol, water, and stearic acid on selected physical and functional properties of the films were studied. The tensile strength, tensile strain at break, and Young's modulus were 0.23–2.91 MPa, 45.79–90.83%, and 2.89–37.94 MPa, respectively. Differential scanning calorimetry thermograms exhibited two glass transitions and multiple melting endotherms, including that of amylose‐lipid complexes formed during extrusion. The enthalpy of gelatinization of starch in the extruded films was 0.7–4.1 J/g and was dependent largely on the plasticizer content. Fourier‐transform infrared spectra revealed significant interactions between the starch and plasticizer but the peaks shifted to higher wave numbers with increasing glycerol content. During extrusion in the presence of glycerol, the A‐type crystalline structure of starch was transformed to B‐type. It also was observed that the Vh crystallinity increased with increase in glycerol content due to tight packing of starch chains. The water vapor permeabilities of the starch films were 12.3–19.9 g·mm/hr·m2·kPa.

Surface modification of starch nanocrystals through ring‐opening polymerization of ε‐caprolactone and investigation of their microstructures

AbstractBionanoparticles of starch obtained by submitting native potato starch granules to acid hydrolysis conditions. The resulted starch nanoparticles were used as core or macro initiator for polymerization of ε‐caprolactone (CL). Starch nanoparticle‐g‐polycaprolactone was synthesized through ring‐opening polymerization (ROP) of CL in the presence of Sn(Oct)2 as initiator. The detailed microstructure of the resulted copolymer was characterized with NMR spectroscopy. Thermal characteristic of the copolymer was investigated using DSC and TGA. By introducing PCL, the range of melting temperature for starch was increased and degradation of copolymer occurred in a broader region. X‐ray diffraction and TEM micrographs confirmed that there was no alteration of starch crystalline structure and morphology of nanoparticles, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Study on the morphology, crystalline structure and thermal properties of yam starch acetates with different degrees of substitution

This study was carried out to understand and establish the changes in physicochemical properties of starch extracted from Chinese yam (Dioscorea opposita Thunb.) after acetylation. Yam starch acetates with different degrees of substitution (DS) were prepared by the reaction of yam starch with glacial acetic acid/acetic anhydride using sulfuric acid as the catalyst. Their formation was confirmed by the presence of the carbonyl signal around 1750 cm−1 in the Fourier transform infrared (FT-IR) spectra. The thermal behavior of the native starch and starch acetate were investigated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results reveal that the starch acetates are more thermally stable than the native starch. The starch esters showed 50% weight loss at temperatures from 328°C to 372°C, while the native starch underwent 50% weight loss at 325°C. The glass transition temperature (Tg) of the starch decreased from 273°C to 226°c. The X-ray diffraction (XRD) patterns could be classified as typical of the C-type for yam starch. X-ray diffraction also showed the loss of the ordered C-type starch crystalline structure and the degree of crystallinity of starch decreased from 36.10% to 10.96% with the increasing DS. The scanning electron microscopy (SEM) suggested that the most of the starch granules disintegrated with many visible fragments with the increasing DS.

Preparation and crystalline morphology of biodegradable starch/clay nanocomposites

An organically modified clay (o-clay) and a pristine clay (p-clay) were used to prepare biodegradable thermoplastic starch (TPS)/clay nanocomposites by melt processing. The gelatinization behaviour of starch with glycerol/H2O was investigated and the gelatinized temperature (Tgel) was determined using a polarized optical microscopy (POM) equipped with a hot stage. The morphologies of gelatinized starch and extruded starch were revealed by scanning electron microscopy (SEM). Thermal stabilities of starch/clay nanocomposites were evaluated under N2 atmosphere using thermogravimetric analysis (TGA). Transparent films of starch/clay hybrids were fabricated by hot pressing. Intercalation of starch into clay galleries and crystalline structure of starch were investigated using X-ray diffraction (XRD). It was found that the increase in d-spacing of organically modified clay was due to starch molecular intercalation while the increase in d-spacing of pristine clay was mostly caused by glycerol intercalation because of the narrow valid d-spacing of pristine clay and special ring-like monomer of starch. The mechanism of starch intercalation in clay galleries was discussed.

The use of micro-beam X-ray diffraction for the characterization of starch crystal structure in rice mutant kernels of waxy, amylose extender, and sugary1

Micro-beam X-ray diffraction analyses were carried out on slices from wild-type rice and mutants. The method permitted the crystalline structure to be analyzed with less destruction of cells and fewer artificial effects that occur during the purification of starch from tissue and provided information concerning the localization and crystalline structure of starches distributed in the endosperm. The starch on kernel slices from the wild-type and waxy mutant, carrying a defect for the Granule-bound starch synthase I ( GBSSI) gene, displayed an A-type of diffraction pattern; no difference in the crystalline patterns between starches located in the inner and outer region in a kernel were observed. A double mutant of the waxy and amylose extender ( ae) mutant carrying a defect for the Starch branching enzyme IIb gene accumulated amylose-free B-type starches. The kernel slice from the double mutant of waxy and sugary1, mutated on the Isoamylase I locus, displayed an A-type diffraction pattern in the outer region and was amorphous in the inner region. A chain-length distribution analysis of polyglucans in kernels from wild-type and mutants showed that ae amylopectin had more long chains and less short chains than the wild-type and waxy amylopectin. On the other hand, the water-soluble polysaccharide in the inner region of the sugary1 endosperm had more short chains than the amylopectin in the outer region counterparts. These results indicate that branch chain length in amylopectin is crucial in determining the formation of A- and B-type starches.

Low temperature post-harvest storage of New Zealand Taewa (Maori potato): Effects on starch physico-chemical and functional characteristics

Fresh tubers from four traditional Taewa (Maori potato) cultivars (Karuparera, Tutaekuri, Huakaroro and Moemoe) and one modern potato cultivar (Nadine) of New Zealand, were stored at 4 °C and 80–90% relative humidity for six months after harvest. Starch was isolated from tubers after every three month period, and its physico-chemical and functional properties measured. Considerable changes in these properties occurred during storage. The extent of changes varied significantly from cultivar to cultivar. Starch swelling power, solubility and light transmittance decreased during tuber storage while a slight increase was observed in starch amylose content. The starch granule size distribution shifted to smaller granule size during tuber storage. Scanning electron micrographs showed degradation/erosion and pitting on the surfaces of many of the starch granules isolated from stored tubers. Transition temperatures and enthalpies of gelatinization of the starches increased somewhat during tuber storage, suggesting that changes in the stability of starch crystalline structures had occurred. Pasting, viscoelastic and texture profile analysis (TPA) characteristics of starch gels were found to have been influenced by tuber storage time for all the cultivars, but to the greatest extent for Nadine and Huakaroro. Gels made from starches from the stored tubers had a reduced tendency towards retrogradation as evidenced by the decrease in syneresis (%) during gel storage at 4 °C.

Self-Association and Crystallization of Amylose

Amylose, the linear constituent of starch, consists of α(1,4)-linked glucose monomers. Although weakly involved in the crystalline structure of starch, it can be recrystallized in a variety of allomorphic types, including those encountered in native starch (A- and B-types). Amylose can either be extracted from starch or produced in vitro by enzymatic synthesis using amylosucrase or phosphorylase. Recrystallization and self-association of amylose in aqueous solutions have been widely studied to understand both the crystallization of starch during biosynthesis and the structural changes that occur during starch processing. Depending on the chain length, concentration, and temperature, gels, spherulites, or lamellar crystals can be formed with A or B allomorphic type. Other ligand-dependent allomorphs (the various V-types) are obtained when amylose is complexed with molecules such as alcohols, lipids, or flavours. Amylose also self-associates into networks, spherulites, or axialites during in-vitro enzymatic synthesis by amylosucrase. When a highly branched acceptor like glycogen is used, dendritic nanoparticles are formed by elongation of the external chains. The recrystallization of amylose extracted from starch and the self-association of amylose during its in-vitro synthesis are described. The amylose properties are discussed in terms of polymer behaviour and model systems to investigate the structure and formation of starch granules.

Amaranth starch-rich fraction properties modified by high-temperature heating

The effect of high-temperature fluidized-bed heating on some properties of an amaranth high-starch fraction obtained from Amaranthus cruentus grains was evaluated. A two-factor at three levels factorial experimental design (3 2) was adopted, one factor being the heating temperature (190, 200 and 210 °C) and the other, the moisture content of the high-starch fraction (12%, 16% and 20% wet basis). The effects on the responses water solubility, swelling power, amylographic and dynamic responses, crystallinity degree and gelatinization enthalpy were established by using response surface methodology. A partial loss of starch crystalline structure was observed but most of their granular integrity was preserved. As temperature and moisture increased, loss of crystalline structure and degree of gelatinization also increased. The obtained amaranth high-starch flours were of a solid character at low temperature, with high consistency when cooked and low water solubility, which make them suitable for industrial applications.

Thermo-physical assessment of bread during staling

Staling of bread is a highly complex phenomenon that is not yet fully understood. This study examined the effect of staling on thermal (DSC) and thermo-physical (DMA) properties of bread. The staling process increased water migration from the crumb to the crust and increased unfreezable water (UFW) fraction. Amylopectin retrogradation incremented during bread staling, and it was showed that the loss in freezable water (FW) was caused from water incorporation into the starch crystalline structure and water migration from the crumb to the crust. DMA was able to follow the shrinking behavior of bread crumb during freezing. Crumb shrank through the entire cooling and freezing process. The matrix shifts through their freezing process incremented the rate of their contraction, probably due to the matrix dehydration as consequence of ice formation. The ageing process changes the thermo-mechanical profile of the crumb, and it was showed that a greater amount of retrogradated starch, affected significantly the contraction capacity of bread crumb.

Starch Nanocrystals with Large Chain Surface Modifications

Nanoscale monocrystalline starch particles were successfully modified using stearic acid chloride and poly(ethylene glycol) methyl ether. Surface modification was confirmed using FTIR, XPS spectroscopy, and contact angle measurements. X-ray diffraction and DSC analysis confirmed that there was no alteration of the starch crystalline structure due to the surface modification. The grafts at the starch surface were also found to crystallize on the surface. TEM showed the individualization of nanoparticles as a result of the reduction of polar and hydrogen bonding forces. These results show our ability to modify the starch nanocrystal surface with plasticizing chains. Modified nanoparticles can find applications as compatibilized polymer additives, surface-active particles, and co-continuous nanocomposite precursors.

Amaranth starch-rich fraction properties modified by extrusion and fluidized bed heating

Today amaranth is a promising food source yet its technological properties are not well known. The modification of some properties of an amaranth starch-rich fraction by a controlled heating is studied. This fraction was obtained by the differential milling of Amaranthus cruentus grains. Tests were performed by both fluidized bed and extrusion heating, according to a factorial experimental design of two variables: temperature and moisture, at three levels 150–170–200 °C and 120–160–200 g/kg wb, respectively. Effects were evaluated by the ANOVA method. As responses, solubility and water absorption, amylographic and dynamic rheological properties, crystallinity, granular integrity and resistant starch content were evaluated. Flours obtained from samples heated by fluidized bed gave aqueous dispersions with high consistencies when cooked, and they had low solubility in water and preserved part of the starch crystalline structure. Flours obtained from extrusion-heated samples gave very high solubility in water but had lower consistency of the aqueous dispersions when cooked, and they showed a complete loss of the crystalline and granular structure. By applying each of the two heating processes, it was possible to modify, according to selected targets, the amaranth starch-rich fraction, what would allow to obtain pre-cooked amaranth flours with a wide range of hydration and rheological properties.

The Deterioration of Eating and Cooking Quality Caused by High Temperature During Grain Filling in Early‐Season indica Rice Cultivars

AbstractThe effect of temperature during grain filling on eating and cooking quality of early‐season indica rice was investigated by using four cultivars with different amylose content. Starting from flowering stage until maturity, the plants of all cultivars were subjected to two temperature treatments, referred as optimum (mean daily air temperature, 22 °C) and high (32 °C) temperature regimes. The results showed that the effect of high temperature on apparent amylose content and gel consistency in milled rice was cultivar‐dependent. Under high temperature, amylose content increased for cv. Jiayu353 and remained little changed for cv. Guangluai4, which had intrinsically higher amylose content, and decreased for cv. Zhefu49 and cv. Jiazao935, which had lower amylose content. By contrast, high temperature reduced or kept stable gel consistency values for cultivars with higher amylose content and increased gel consistency values for those with lower amylose content. Moreover, high temperature significantly increased the gelatinization temperature of all cultivars. Pasting profiles and X‐ray diffraction pattern of rice were also affected by temperature. The results suggest that high temperature during grain filling change the component and crystalline structure of starch and result in deterioration of eating and cooking quality for early‐season indica rice.