Gelatinization Mechanism of Rice Starch

ABSTRACT

The non-Newtonian behavior and dynamic viscoelasticity of rice starch (Nihonbare; amylose content, 15.8%) solutions were measured with a rheogoniometer. A gelatinization of Nihonbare starch occurred above 3.0% after heating at 100 °C for 30 min. The Nihonbare starch showed shear-thinning behavior at a concentration of 2.0%, but plastic behavior above 3.0% at 25 °C. The viscosity of Nihonbare starch at a concentration of 2.0% solution decreased gradually with increase in temperature from 10 to 55 °C, then it stayed at a constant value with further increase in the temperature. However, for 4.0% solution, rapid decrease in the viscosity was observed after the temperature reached 25 °C up to 50 °C, then it stayed at a constant value. The dynamic modulus of Nihonbare starch stayed at a constant value during increase in the temperature at 4%. The tan δ of the starch showed low values, 0.28, at low temperature range and stayed at a constant up to 30 °C, then it increased a little with increasing temperature. A little decrease of dynamic modulus of Nihonbare starch was observed at low temperature range upon addition of urea (4.0 M). The dynamic modulus, however, decreased rapidly when the temperature reached 50 °C, which was estimated to be a transition temperature. The dynamic modulus also decreased rapidly in 0.10 M NaOH solution above 50 °C. A possible mode of intermolecular hydrogen bonding between amylose and amylopectin molecules of Nihonbare starch is proposed. The short chains (A and B1) of the amylopectin molecules may take part in the intermolecular association in aqueous solution.     

Development and characterization of biodegradables packaging obtained from biopolymers mixture

The aim of this work is the development and the characterization of biodegradables films obtained from a mixture of soluble starch and sodium alginate. The influence of sodium alginate ratio on the behavior of these films is also studied in order to use them as new formulations to produce food packaging. The obtained films are generally homogeneous, thin, smooth and having a good coherence with no visual defects. The results of the FITR, SEM and XRD tests have shown the existence of a good compatibility, between alginate and starch due to both kind of strong interactions like hydrogen bonds and ionic interactions. Water sorption isotherm, water vapor permeability, and mechanical tests were strongly influenced by the addition of sodium alginate in the different formulations. This influence is caused by the plasticization effect of sodium alginate.     

Physical,Chemical and Rheological Characterization of Tuber and Starch from Ceiba aesculifolia subsp. parvifolia

This work aimed to evaluate the physical, chemical and antioxidant properties of Ceiba aesculifolia subsp. parvifolia (CAP) tuber and determinate rheological, thermal, physicochemical and morphological properties of the starch extracted. The CAP tuber weight was 3.66 kg; the edible yield was 82.20%. The tuber presented a high hardness value (249 N). The content of carbohydrates (68.27%), crude fiber (15.61%) and ash (9.27%) from the isolated starch, reported in dry weight, were high. Phenolic compounds and flavonoid content of CAP tuber peel were almost 3-fold higher concerning the pulp. CAP tuber starch exhibited a pseudoplastic behavior and low viscosity at concentrations of 5–15%. Purity percentage and color parameters describe the isolated starch as high purity. Thermal characteristics indicated a higher degree of intermolecular association within the granule. Pasting properties describes starch with greater resistance to heat and shear. CAP tuber starch has X-ray diffraction patterns type A. The starch granules were observed as oval and diameters ranging from 5 to 30 µm. CAP tuber could be a good source of fiber and minerals, while its peel could be used for extracting bioactive compounds. Additionally, the starch separated from this tuber could be employed as a thickening agent in food systems requiring a low viscosity and subjected to high temperatures.     

Effects of chemical modification on the structure and mechanical properties of starch-based biofilms

Abstract  

In this work, chemically modified corn starch and plasticized corn starch biofilms were obtained and characterized in four steps: (1) preparation of corn starch microparticles, (2) preparation of malic acid-modified corn starch microparticles (MA–SM), (3) preparation of corn starch biofilms and MA–SM-plasticized corn starch biofilms, and (4) characterization of the biofilms. The effects of MA–SM concentration (4, 8, and 12% based on the amount of corn starch) on the structural characteristics and mechanical properties of the biofilms were investigated. Changes in the starch granules after chemical modification were studied by X-ray diffraction, FT-IR spectroscopy, and scanning electron microscopy. The presence of ester carbonyl group stretching vibration at 1,720 cm⁻¹ in FT-IR spectra was evidence of reaction of the starch microparticles with malic acid. The tensile yield strength and Young’s modulus of the films increased with increasing MA–SM content. Water uptake decreased from 69.8% for biofilm without MA–SM to 52.7% for biofilm with MA–SM. The improvement of these properties in the plasticized product could be attributed to the good interaction between the MA–SM filler and the corn starch.     

Radical Polymerization of Vinyl Monomers by Hydrophilic Macromolecules. I. Uncatalyzed Polymerization in the Absence of Copper(ll) Ions

Abstract

In 1962 Kimura, Takitani, and Imoto [1] found that an aqueous solution of starch could easily polymerize methyl methacrylate (MMA), and about one-half of the polymerized MMA was grafted on to starch. This novel polymerization was called “uncatalyzed polymerization.” Since then, a large number of macromolecules other than starch have been studied, and many of them are effective for initiating the radical polymerization of MMA.     

Determination of Damaged Starch in Wheat Flour Using an Electrochemical Bienzyme Maltose Probe

Abstract

The development of an electrochemical biosensor based on a bienzyme maltose probe and a third enzyme α-amylase in solution is reported for the rapid and inexpensive determination of damaged starch. Analytical parameters, such as probe stability, pH, temperature and response time, were optimised. Damaged starch was measured in the range of 5 × 10^?6 - 5 × 10^?4 mol/L as maltose produced by the enzymatic reaction and the detection limit was calculated according with the free maltose and/or glucose in the sample. The damaged starch was determined in different wheat flours, and the data significantly correlated with those obtained using a reference procedure (r² = 0.994; P ≤ 0.0001). In addition the results showed a comparable precision (CV < 5%). This method is rapid, inexpensive and friendly for unskilled operators.     

Effects of Poly(Ethylene Glycol) on the Physical Properties of Blended Molecules of Starch and Poly(Ethylene-co-Acrylate,Ammonium Salt)

Abstract

A mixture of starch (36%) poly(ethylene-co-acrylate, ammonium salt) (41%), water (12.5%), urea (8.4%), and poly(ethylene glycol) (M _n 4600) (2.1%) were converted to plastic test pieces by extruding (130°C), drying and grinding (25°C), and hot pressing (175°C). After equilibration at ?50% relative humidity and 25°C, the test pieces contained 3.5–4.6% moisture and 2.3% poly(ethylene glycol) (PEG). Among wheat, corn, potato, and rice starches, the wheat starch (WS) blend showed the highest Young's modulus (181.3 MPa), whereas the corn starch (CS) blend had a modulus and elongation that almost matched those of lowdensity polyethylene. When PEG was eliminated from the WS formulation, tensile strength remained constant, but Young's modulus doubled. The modulus decreased continually as test pieces absorbed water up to 27% moisture, but elongation and argon laser light transmittance were optimum at ?12% moisture. Differential scanning calorimetry indicated that PEG formed a solid inclusion complex with amylose upon drying at 60°C, but no complex was detected in dilute alkali by optical rotation.     

Chemical constituents from the flowering buds of Bauhinia tomentosa Linn (FBBT)

Isolation and characterisation of compounds, 1-(2′-hydroxy-4′-methoxyphenyl)-3-(4″-methoxyphenyl)-2-hydroxypropane-1,3-dione (1), 5-hydroxyflavone (2), 3,5,7,3′,4′-pentahydroxyflavone (3), 3,5,7,2′,4′-pentahydroxyflavone (4) and 5,7,3′,4′-tetrahydroxyflavone-3-O-rhamnoside (5) are reported from the air dried flowering buds of Bauhinia tomentosa Linn. Their structures are determined on the basis of extensive chemical and spectral evidences. Compound (1) is reported for the first time from the plant source. While compounds (2) and (4) are reported for the first time from this genus, compound (2) is reported for the second time from the natural source.     

Properties of Starch Blends with Biodegradable Polymers

Abstract

Starch, one of the most inexpensive and most readily available of all natural polymers, can be processed into thermoplastic materials only in the presence of plasticizers and under the action of heat and shear. Poor water resistance and low strength are limiting factors for the use of materials manufactured only from starch, and hence the modification of starch is often achieved by blending aliphatic polyesters. In this review, the literatures concerning the properties of various blends of starch and aliphatic polyesters have been summarized. The biodegradable rates of blends can be controlled to a certain extent depending on the constitutions of blends, and the mechanical properties of blends are close to those of traditional plastics such as polyethylene and polystyrene. The reduction of their sensitivity to humidity makes these materials suitable for the production of biodegradable films, injection-molded items, and foams.     

Immobilization of Amylases on Silica Support to Study Breakdown Products of Potato Starch by HPLC

Abstract

Immobilization of α- and β-amylases on epoxypropylsilanized PartiSphere-5 was achieved. Hydrolysis of 2% potato starch solution yielded limit dextrin on α-amylase bound column while a mixture of limit dextrin, maltose and glucose was obtained from β-amylase bound column. The β-amylase bound column converted limit dextrin from α-amylase column into glucose.     

Oxidation of Methyl 4,6-O-Isopropylidene-α-d-glucopyranoside as a Model Compound for Starch

Abstract

The oxidation of methyl 4,6-O-isopropylidene-α-d-glucopyranoside (1) via various routes to the dicarboxylate 2 is described. This reaction is used as a model for the oxidation of starch to dicarboxylic starch, a material with very promising properties as a cobuilder in detergents. The best oxidant found for C₂-C₃ cleavage was RuO₄, prepared in situ by oxidation of a catalytic amount of Ru^III with NaOCl.     

The Unit-Subduced-Cycle-Index Methods and the Characteristic-Monomial Method. Their Relationship as Group-Theoretical Tools for Chemical Combinatorics

Among the four methods of the unit-subduced-cycle-index (USCI) approach, the subduced-cycle-index (SCI) method and the partial-cycle-index (PCI) method have been discussed by using adamantane of T _d -symmetry as a probe for enumeration problems, where USCIs are derived on the basis of permutaion representations, coset representations (CRs) and marks. After the examination of the SCIs and PCIs, Pólya's theorem that is a standard method of chemical combinatorics has been derived from the USCI approach. As another approach, a new method called the characteristic-monomial (CM) method has been developed by virtue of charactereistic monomials (CMs). The CMs have been derived from Q-conjugacy representations and Q-conjugacy characters, which have been related to irreducible representations and irreducible characters of the standard repertoire of chemical group theory. The two approaches have been compared to discuss group-theoretical tools for chemical combinatorics on a common basis.     

Ab initio studies of NMR chemical shifts for calix[4]arene and its derivatives

Ab initio calculations are performed for the calix[4]arene (1) and its derivatives (2 and 3), in this study. ¹H and ¹³C NMR measured spectral data given in our previous work are used to elucidate the structures of the prepared calix[4]arenes (1–3). The molecular geometry and chemical shift are calculated by using ab initio calculations based on the Hartree-Fock (HF) and the density functional theory (DFT) in the ground state. The results obtained from both methods are in agreement with the experimental results. The results of molecular geometry and chemical shifts show that DFT approach is closer to the experimental data than HF method.     

Alcohol separation by thin-layer chromatography. II

Summary Thin-layer chromatography on rice starch, maize starch, cellulose and talc makes possible the separation of the homologous series of 3,5-dinitrobenzoates of aliphatic alcohols C₁ to C₂₀. Six different solvent systems have been employed. Dependence of R _f-values on the number of C-atoms on various supports is discussed.Part I: Fresenius Z. Anal. Chem. 264, 415 (1973)     

Synthesis and characterization of a starch‐modified hydrogel as potential carrier for drug delivery system

Synthesis and characterization of a new hydrogel were carried out using a chemically modified starch (starch‐M) consisting of coupling C?C bounds coming from glycidil methacrylate (GMA) onto the polysaccharide structure. ¹³C NMR, ¹H NMR, and FT‐IR spectroscopies were used to confirm the incorporation of such groups onto the starch‐M. The hydrogel was prepared by a crosslinking polymerization of starch‐M using sodium persulfate as an initiating agent. The starch‐M hydrogel shows morphology clearly different from that of the raw starch film due to the presence of voids on its surface. The swelling process of the starch‐M hydrogel was not significantly affected by changes on the temperature or on pH of the surrounding liquid, indicating the such behavior can be then understood by a diffusional process, resulting from its physical–chemical interactions with the solvent. The values of the diffusional exponent n were on the order of 0.45–0.49 for the range of pHs investigated, demonstrating that the water transport mechanism of starch‐M hydrogel is more dependent on Fickian diffusion, that is, controlled by water diffusion. Such starch‐M hydrogel is a promising candidate to be used in transporting and in preserving acid‐responsive drugs, such as corticoids, for the treatment of colon‐specific diseases, for example, Crohn's disease. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2567–2574, 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 tem- peratures from 328℃ to 372 ℃ , while the native starch underwent 50% weight loss at 325℃ . The glass transition temperature (Tg) of the starch decreased from 273℃ to 226℃. 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 de- creased from 36.10% to 10.96% with the increasing DS. The scanning electron microscopy (SEM) sug- gested that the most of the starch granules disintegrated with many visible fragments with the in- creasing DS.     

Conformational contribution to the heat capacity of the starch and water system

The heat capacities of starch and starch—water have been measured with adiabatic calorimetry and standard differential scanning calorimetry and are reported from 8 to 490 K. The amorphous starch containing 11–26 wt % (53–76 mol %) water shows a partial glass transition decreasing from 372 to 270 K, respectively. Even the dry amorphous starch gradually increases in heat capacity above 270 K beyond that set by the vibrational density of states. This gradual increase in the heat capacity is identified as part of the glass transition of dry starch that is, however, not completed at the decomposition temperature. The heat capacities of the glassy, dry starch are linked to an approximate group vibrational spectrum with 44 degrees of freedom. The Tarasov equation is used to estimate the heat capacity contribution due to skeletal vibrations with the parameters Θ₁ = 795.5 K, Θ₂ = 159 K, and Θ₃ = 58 K for 19 degrees of freedom. The calculated and experimental heat capacities agree better than ±3% between 8 and 250 K. Similarly, the vibrational heat capacity has been estimated for glassy water by being linked to an approximate group vibrational spectrum and the Tarasov equation (Θ₁ = 1105.5 K and Θ₃ = 72.4 K, with 6 degrees of freedom). Below the glass transition, the heat capacity of the solid starch—water system has been estimated from the appropriate sum of its components and also from a direct fitting to skeletal vibrations. Above the glass transition, the differences are interpreted as contributions of different conformational heat capacities from chains of the carbohydrates interacting with water. The conformational parts are estimated from the experimental heat capacities of dry starch and starch—water, decreased by the vibrational and external contributions to the heat capacity. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 3038–3054, 2001     

Synthesis of Poly(Ethylene Glycol)–Supported (R)-BINOL Derivatives and Their First Application in Enantioselective Mukaiyama Aldol Reactions

The Mukaiyama aldol reaction of 2-styryl-oxazole-4-carbaldehyde (1) as model substrate with S-ketene silyl acetal 2 catalyzed by poly(ethylene glycol)-supported binaphthyl-derived chiral titanium(IV) complexes afforded the corresponding aldol product in good to excellent yields and enantioselectivities up to 94% ee. The chemical yields and/or the enantioselectivities are enhanced by generating the active catalyst from Ti(OiPr)₄, polymer-supported ligands (R)-6 or (R)-8, and chiral or achiral promoters. Pyrrolidine derivative (S)-13 and trifluoromethyl-substituted phenol 12 are the most efficient additives found.     

Determination of Fluorine in Vegetation by Proton Activation Analysis

Abstract

Techniques have been developed for proton activation analysis using the ¹⁹F(p,p′y)¹⁹F reaction to measure the fluorine content of pulverized samples of vegetation which have been exposed to fluorides in the atmosphere or soil. The method is non-destructive and neither the chemical form of fluorine in the sample nor the type of vegetation analyzed appears to affect results. Calibration is performed by analyzing samples to which known amounts of fluorine are added. The fluorine content of 11 vegetation samples was determined by proton activation analysis and by standard chemical techniques. The values obtained by the two methods were in generally good agreement. Fluorine concentrations greater than 1 ppm can be measured with uncertainties ranging from about 50% at 5 ppm to less than 10% at concentrations above 50 ppm.     

Preparation and properties of carboxyl-functional mixed esters of hydrolyzed starch

Mixed esters of hydrolyzed starch represent a new class of chemically modified natural polymers demonstrating a broad range of properties. Members of this class of polymers have both neutral aliphatic ester side chains and carboxyl-functional half-ester side chains. Use of hydrolyzed starch as the backbone polymer results in products that are considerably lower in molecular weight than whole starch derivatives, but which are still polymeric in character. Synthesis proceeds smoothly in pyridine using anhydrides as acylating agents and the pure solid mixed ester products are isolated by precipitation in water. Measurement of degree of substitution (D.S.) by NMR or hydrolysis characterizes the chemical composition of the polymers. The actual D.S. achieved in the synthesis depends upon the competition between starch and residual water for anhydrides, which can be quantitatively evaluated by monitoring the acid content of the reaction mixture. The T_g and T_s of starch mixed esters vary with both D. S. and length of the aliphatic ester side chain. As the composition changes from acetate—phthalate to butyrate—phthalate a T_g range of greater than 100°C is observed. Hydrolyzed starch mixed esters are hydrophobic and organic-soluble, but may be readily solubilized in aqueous base through the half-ester groups. Solutions show surface activity which varies according to the type and extent of substitution.