The effect of amylose content from differing botanical sources on the nonlinear viscoelastic properties of semidilute solutions of maize starches*

The effect of the addition of potato or maize on the shear-thickening behavior of semidilute solutions of maize was examined. The experiments were conducted at 25°C using 90/10 weight–weight dimethyl sulfoxide (DMSO)–water as the solvent. The addition of amylose to maize amylopectin reduced and eventually eliminated the observed shear-thickening behavior of maize amylopectin. When potato amylose was combined with maize amylopectin, the shear-thickening phenomenon was observed up to a total amylose content of 10% by weight. For maize amylose, the shear-thickening behavior was eliminated at an amylose content of 5%. Maize amylose is thus more effective in inhibiting the formation of the structure formed after the shear-thickening region than potato amylose. This result indicates that the amylose obtained from potatoes interacts differently, or entangles differently, with maize amylopectin than does the amylose obtained from maize. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2429–2436, 1999     

Viscoelastic properties of plasticized amylose films

The viscoelastic properties of amylose films plasticized with dimethyl sulfoxide were studied. The modulus–temperature curves of dimethyl sulfoxide-plasticized amylose are typical for semicrystalline polymers at the higher concentrations of amylose and pass to those of amorphous polymers with the decrease of amylose content. The glassy modulus is not affected by the incorporation of dimethyl sulfoxide, but the rubbery modulus and T_g are depressed with increased dimethyl sulfoxide. The change of T_g with plasticization can be represented by two approximately straight lines, one representing the lower concentration region of amylose and the other the higher one. The critical concentration is about 60% amylose. When the results of modulus–time measurements and x-ray diffraction are considered together, in a system of amylose–dimethyl sulfoxide, amylose exists as a semicrystalline polymer at high concentrations of amylose, and it acts intermediate between semicrystalline and amorphous polymers at lower concentrations below about 60%. From an extrapolation of the data of T_g of plasticized amylose, T_g of pure amylose appears to be approximately 330°C. The viscoelastic properties of amylose films plasticized with dimethyl sulfoxide–sorbitol mixtures were also studied.     

Biodegradable starch particles for controlled release applications: Swelling and leaching mechanisms

Starch-extruded particles have only found infrequent use as delivery systems for active ingredients. We have previously shown that these particles are attractive for releasing hydrophobic compounds in water media. Here, we cover a range of amylose–amylopectin ratios and evaluate the presence of the thyme essential oil (TEO) as active compound to understand the dominant release mechanism in relation to the physicochemical properties of the starch matrices. Starch blends with high amylopectin content (1.8 and 15% amylose) could not be shaped into regular particles. For amylose contents higher than 28%, the equilibrium degree of swelling in water decreased with increasing amylose contents, from nearly 300% for an amylose content of 28–90% at an amylose content of 70%. For both lowest amylose contents, 1.8 and 15%, leaching of solids and disintegration of the particles resulted in a low apparent degree of swelling. The presence of TEO reduces the degree of swelling of the gelatinized starch matrix. This is explained by the formation of thymol–amylose complexes, which is confirmed by Fourier transform infrared spectroscopy analysis and X-ray diffraction.     

Viscoelastic properties of plasticized amylose triacetate films

The viscoelastic properties of amylose triacetate films plasticized with diisobutyl phthalate were studied. The modulus–temperature curves of diisobutyl-phthalate-plasticized amylose triacetate are typical for amorphous polymers with the decrease of amylose triacetate content. The glassy modulus is not affected by the incorporation of diisobutyl phthalate, but the rubbery modulus and glass transition temperature are depressed with increased diisobutyl phthalate. The rubbery modulus appears at first to maintain for a wide temperature range, then disappears with increased diisobutyl phthalate. From the results of modulus–time measurements and x-ray diffraction patterns: in a system of amylose triacetate–diisobutyl phthalate, amylose triacetate exists as an amorphous polymer at all concentrations of amylose triacetate and it acts intermediately between semicrystalline and amorphous polymers at lower concentrations below about 90%.     

Complexes of starch polysaccharides and poly(ethylene co-acrylic acid): Structure and stability in solution

Chiroptical methods have been used to study the conformation and interactions of amylose and amylopectin with poly(ethylene co-acrylic acid) (EAA) in aqueous solution. These studies, along with X-ray diffraction and solid-state NMR data, show that amylose and EAA, as well as amylopectin and EAA, form helical V-type inclusion complexes when mixed in aqueous suspension. This structure apparently accounts for the partial compatibility observed in films containing starch and EAA. About 2/3 by weight of EAA does not interact with amylose and probably represents the ethylene-rich central core of the EAA micelle. EAA/amylose complexes in 10 mM NaOH were stable to temperatures > 90°C, whereas EAA/amylopectin complexes in the same solvent were largely disrupted at this temperature. Urea, at a concentration of 8 M, further destabilized both EAA/amylopectin and EAA/amylose complexes. Solutions with an alkaline pH (> 9.5) dispersed EAA optimally and allowed maximum complexing with amylose. At pH values > 13, the EAA/amylose complexes were weaker, most likely due to electrostatic repulsion between ionized hydroxyl groups of amylose and carboxyl groups of EAA.     

Further insight for the synthesis of 6-amino-6-deoxy amylose

Because 6-amino-6-deoxy amylose is an important intermediate for many materials, developing a practical pathway to easily prepare it in bulk is of significance. The synthesis of 6-amino-6-deoxy amylose included three reactions. In the chlorination reaction, the crude product could be fully de-esterified under the improved conditions, and the reaction mechanism was re-understood. The azido group was reduced with sodium borohydride in which the reaction conditions were studied in detail. With the improved synthetic pathway, 6-amino-6-deoxy amylose could be easily prepared. The 6-amino-6-deoxy amylose was characterized via its benzamide derivative with ¹H NMR, ¹H-¹³C HSQC NMR, and ¹H-¹H COSY NMR, confirming the hydroxyl group at C₆ of amylose was converted to amino group with a degree of substitution of 98.2%. Additionally, the 6-amino-6-deoxy amylose was analyzed toward iodine reagent and X-ray diffraction, and the corresponding results showed that it was different from amylose in suprastructure and crystal structure.     

Evidences of amylose coil-to-helix transition in stored dilute solutions

Static (SLS) and dynamic (DLS) light scattering measurements were performed in order to study the conformational changes in amylose during storage in alkaline (KOH) and briny (KCl) aqueous solutions. Immediately after dissolution, amylose was structured as random coil and the polymer architecture was not affected by the electrolyte concentration. In stored samples the electrolyte concentration played a more important role. Although no general trend for the radii variation, depolymerisation process was not detected and an increase in the scattered light depolarization ratio was evidenced, being more pronounced for amylose chains stored in KOH. This behavior was attributed to a coil-to-helix transition in the amylose chains. Hence, the presence of precipitation after ∼30 days of storage suggests the helix amylose crystallization.     

Application of deaerated water in swelling of cellulose and amylose and cotton desizing with enzyme

The effect of deaerated water on the swelling of cellulose and amylose and on the application in cotton desizing with enzyme that contains necessarily these swelling processes were studied. The total volume changes of the swelling of cellulose and amylose were measured by dilatometry. The total volume changes of cellulose and amylose were more negative in deaerated water. In deaerated water, the total volume changes are 142 ± 6% for cellulose and 229 ± 2% for amylose to those in air‐present water. The rates of cotton desizing with two kinds of enzymes were studied by measuring the concentration of generated sugars by using HPLC. Higher efficiency of 140–150% was obtained in deaerated water than in water containing dissolved gases of air, oxygen, or nitrogen. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1693–1700, 1999     

The unwinding of surfactant-induced helical structure of carboxymethyl amylose by single molecule force spectroscopy

We have employed atomic force microscopy (AFM)-based single molecule force spectroscopy (SMFS) to investigate the unwinding process of the surfactant-induced helical structure of carboxymethyl amylose at the single-molecular level. In doing so, the nanomechanical fingerprint for the conformational transition of carboxymethyl amylose at about 270 pN is used as an indicator for identifying the single chain elongation. Upon the addition of NaCl and cetyltrimethylammonium bromide (CTAB), the force-extension curve of carboxymethyl amylose appears as a long flat plateau during the elongation of a single chain followed by the conformational transition. The flat plateau is attributed to the unwinding process of CTAB-induced helical structure of carboxymethyl amylose. By Gaussian fitting, the center value for plateau height histogram is 17 pN, which reflects the force needed to unwind the CTAB-induced helical structure of carboxymethyl amylose. We hope that this line of research provides an example of using characteristic shoulder plateau of α-linked glycan to identify single chain elongation, allowing for direct measurement of the unwinding force of supramolecular structure using SMFS.     

Structure‐Property Relationships in Extruded Starch, 1 Supermolecular Structure of Pea Amylose and Extruded Pea Amylose

Separated amyloses with different molecular weight distributions were obtained enzymatically from wrinkled pea starch and processed in a multi‐zone twin‐screw extruder. The crystalline polymorphs, crystallinity and crystallite dimensions of amylose (unbranched molecular starch component) and films extruded from it were investigated by wide‐angle X‐ray scattering. The starting amylose materials exhibit a crystalline V_A structure with rather large crystallites (9–25 nm) and a degree of crystallinity ranging between 30 and 40%, depending on the history of the amylose sample. The extruded films, on the other hand, recrystallized in the B‐type with a slightly higher degree of crystallinity and significantly smaller crystallite dimensions (3–7 nm). In one case, V_H‐type crystals were observed. The mechanical properties of the extruded materials were determined in tensile tests. The amylose with the highest molar mass produces films with the highest mechanical performance. As compared with cellulose or synthetic polymer films, the mechanical properties of the amylose films appear to be fundamentally limited by the lack of preferred molecular orientation.     

CRISPR/Cas9-Mediated Mutagenesis of the Granule-Bound Starch Synthase Gene in the Potato Variety Yukon Gold to Obtain Amylose-Free Starch in Tubers

Potato (Solanum tuberosum L.) is the third most important food crop after rice and wheat. Its tubers are a rich source of dietary carbohydrates in the form of starch, which has many industrial applications. Starch is composed of two polysaccharides, amylose and amylopectin, and their ratios determine different properties and functionalities. Potato varieties with higher amylopectin have many food processing and industrial applications. Using Agrobacterium-mediated transformation, we delivered Clustered regularly interspaced short palindromic repeats and CRISPR-associated protein 9 (CRISPR/Cas9) reagents to potato (variety Yukon Gold) cells to disrupt the granule-bound starch synthase (gbssI) gene with the aim of eliminating the amylose component of starch. Lugol-Iodine staining of the tubers showed a reduction or complete elimination of amylose in some of the edited events. These results were further confirmed by the perchloric acid and enzymatic methods. One event (T2-7) showed mutations in all four gbss alleles and total elimination of amylose from the tubers. Viscosity profiles of the tuber starch from six different knockout events were determined using a Rapid Visco Analyzer (RVA), and the values reflected the amylopectin/amylose ratio. Follow-up studies will focus on eliminating the CRISPR components from the events and on evaluating the potential of clones with various amylose/amylopectin ratios for food processing and other industrial applications.     

Quality Attributes of Germinated High-Amylose and Waxy Rice in Superheated Steam and Hot Air Drying

In this work, the effects of amylose content, drying medium, and drying temperature on the fissure, texture, and glycemic index of germinated paddy (GP) were investigated. The amylose content, drying temperature, and drying medium affected the degree of starch gelatinization and percentage of fissure kernels significantly. Hot air drying at 130 and 150°C insignificantly influenced the hardness of Phitsanulok 2 GP with high amylose content after cooking compared to that of shade-dried GP, and the drying temperatures significantly affected the hardness and stickiness of RD6 GP without amylose content. Superheated steam drying caused a significant change in textural properties for both paddy varieties because of complete starch gelatinization. The high-amylose paddy had higher gamma-aminobutyric acid and lower glycemic index than nonamylose paddy. Drying temperature and drying media did not change the gamma-aminobutyric acid and glycemic index of both GP varieties in comparison to their shade-dried samples.     

Functionalization of amylose with chloroacetate groups and their derivation with α-naphthylacetic acid. Heterogeneous hydrolytic behaviour of the resulting adducts

Amylose functionalized with chloroacetate groups was obtained by reaction of amylose with chloroacetyl chloride using pyridine as catalyst and the dimethylformamide/LiCl system as solvent. ¹³C-NMR spectra at 75.4 MHz of partially modified amylose with chloroacetate groups were studied in order to evaluate the selectivity of the reaction of amylose with chloroacetyl chloride in the homogeneous phase. Analysis of the spectra of ring carbons in the anhydroglucose units shows that the reactivity of the individual hydroxyl groups decreases in the order C-6 > C-3 > C-2. The coupling of a model bioactive carboxylic acid (a-naphthylacetic acid) to amylose functionalized with chloroacetate groups was carried out by reaction with its potassium salt. High degrees of modification were obtained in all cases. The hydrolysis in the heterogeneous phase of amylose-a-naphthylacetic adducts showed that the release of the bioactive compound is dependent on the sample form and the hydrophilic character of the adduct as well as on the pH value of the medium.     

Synthesis and characterization of acryloyloxystarch

By Schotten-Bauman's esterification of amylose with acryloyl chloride, a new ester derivative of starch—acryloyloxyamylose—was prepared, which contains double bonds. The effects of the reagent ratio, KOH concentration, and reaction time on the degree of amylose esterification were examined. The original amylose and acryloyloxyamylose were characterized by FTIR, ¹H-NMR, ¹³C-NMR, GPC, and DSC. Acryloyloxyamylose was polymerized in solution by the free-radical process and by photopolymerization in a solid state to obtain a crosslinked product. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65 : 2123–2129, 1997     

Solid state and solution features of amylose and amylosic fragments

An understanding of the molecular changes occurring during polymorphic transformations of amylose is sought through the use of energy calculations. Four stable families of low energy conformers are found; three of these correspond to conformations observed in linear and cyclic maltodextrins in the crystalline state. Upon change of solvent, significant variations have been shown to occur in the relative abundance of amylose conformers. This, in turn, influences properties such as chain extension. The relevance of the stable conformers with respect to helical structures of amylose is analyzed. Whereas one of the conformers would generate a V type shallow helix, another one would give rise to a 6 fold left-handed strand having a 3.6 A advance per residue. This would generate a double helical stranded structure.     

Effects of thermal treatment on fish lipids‐amylose interaction

The paper describes a study on effects of thermal treatments (microwave heating and freezing) on fish lipids‐amylose starch interactions. Particular attention was paid to lipid availability (extractability from the system) and contribution of fatty acids to various groups of lipids after interactions produced by mixing, microwave heating and storage. Analyses were made on model systems containing fish lipids at different oxidation levels and gelatinised with 10% aqueous solution of amylose starch. The lipid:starch ratio was 1:1. The systems were assayed before and after mixing, microwave heating (4 min, 90 W), freezing (30 d, –18 °C), and heating followed by freezing. Lipid extractability (selective extraction), peroxide value (PV), anisidine value (AsV), fluorescence, and fatty acid profiles (GC/MS) were determined. Mixing of fish lipids with amylose was shown to result in lipid‐amylose interaction. The thermal treatments applied (microwave heating or freezing at –19 °C for 30 d) were observed to exert different, significant effects on fish lipids‐amylose starch interactions. The effects depended also on the extent of lipid oxidation. Fatty acids of the lipids were bound selectively, PUFA, and particularly DHA, were subjected to stronger binding and higher amounts of those acids were bound.     

Extruded foams prepared from high amylose starch with sodium stearate to form amylose inclusion complexes*

Extruded starch foams were prepared from high amylose corn starch with and without sodium stearate and poly(vinyl alcohol) (PVOH) to determine how the formation of amylose–sodium stearate inclusion complexes and PVOH addition would affect foam properties. X‐ray diffraction and Differential Scanning Calorimetry (DSC) showed that amylose–sodium stearate inclusion complexes were formed by low temperature extrusion and did not dissociate during foam formation by a second extrusion at higher temperatures. In the absence of PVOH, water absorption, and foam shrinkage at 95% RH were decreased because of the hydrophobicity of the complex. PVOH addition increased both the expansion ratio and the shrinkage of the foam, although shrinkage at 95% RH was still less than that observed with uncomplexed amylose. The structural integrity and some tensile properties of stearate‐containing foams were improved by PVOH addition. These results provide the manufacturer of biodegradable starch foams with an inexpensive method for tailoring foam properties for specific end‐use applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43251.     

Simple and rapid molecular techniques for identification of amylose levels in rice varieties

The polymorphisms of Waxy (Wx) microsatellite and G-T single-nucleotide polymorphism (SNP) in the Wx gene region were analyzed using simplified techniques in fifteen rice varieties. A rapid and reliable electrophoresis method, MetaPhor agarose gel electrophoresis (MAGE), was effectively employed as an alternative to polyacrylamide gel electrophoresis (PAGE) for separating Wx microsatellite alleles. The amplified products containing the Wx microsatellite ranged from 100 to 130 bp in length. Five Wx microsatellite alleles, namely (CT)(10), (CT)(11), (CT)(16), (CT)(17), and (CT)(18) were identified. Of these, (CT)(11) and (CT)(17) were the predominant classes among the tested varieties. All varieties with an apparent amylose content higher than 24% were associated with the shorter repeat alleles; (CT)(10) and (CT)(11), while varieties with 24% or less amylose were associated with the longer repeat alleles. All varieties with intermediate and high amylose content had the sequence AGGTATA at the 5'-leader intron splice site, while varieties with low amylose content had the sequence AGTTATA. The G-T polymorphism was further verified by the PCR-AccI cleaved amplified polymorphic sequence (CAPS) method, in which only genotypes containing the AGGTATA sequence were cleaved by AccI. Hence, varieties with desirable amylose levels can be developed rapidly using the Wx microsatellite and G-T SNP, along with MAGE.     

高直链玉米淀粉/PVA复合膜的制备

以高直链玉米淀粉为原料,选用乙二醇为增塑剂,硼砂为交联剂,采用流延法制备淀粉/聚乙烯醇(PVA)复合膜。研究不同直链淀粉含量、增塑剂用量、交联剂用量、等因素对复合膜性能的影响。结果表明,高直链淀粉复合膜的性能明显优于普通淀粉复合膜。当淀粉、乙二醇、硼砂用量分别为20%、30%、5%时,复合膜性能最佳。     

Studies of biodegradable thermoplastic amylose/kaolin composites: Fabrication,characterization, and properties

Biodegradable thermoplastic amylose/kaolin composites (BTAKC) have been fabricated from glycerol‐plasticized amylose (GPA) and inorganic reinforced materials kaolin. Fourier Transform infrared (FTIR) patterns showed that in the BTAKC the C O groups of amylose molecules shifted to the higher wavenumber, while the reactive hydroxyl groups of kaolin in BTAKC shifted to the lower wavenumber. This was caused by the cooperation of strong absorption that existed between kaolin and amylose molecules and hydrogen bonds that formed between the reactive hydroxyl groups of kaolin and the hydroxyl groups of amylose molecules. Kaolin was on the submicron filling transition state and acted as an obstructer. Thermogravimetric analysis (TGA) showed that the mass loss of GPA and BTAKC with 20% kaolin were 15.54 and 13.74% respectively, the thermal stability of BTAKC were improved. When BTAKC was stored for 10 days at Relative Humidity (RH) = 50%, the tensile stress, strain, Young's modulus and breaking energy of BTAKC with 20% kaolin were 9.53 MPa, 65.4%, 149.8 MPa and 1.402 N m respectively. It was obvious that the mechanical properties of BTAKC were greatly improved. X‐ray diffraction revealed that kaolin restrained the crystallization of GPA effectively. Water absorption testing indicated that the introduction of kaolin reduced the water absorption of BTAKC, which greatly improve the application property of BTAKC. Scanning electron microscope (SEM) revealed that kaolin was commendably dispersed in GPA. Polym. Compos. 27:309–314, 2006. © 2006 Society of Plastics Engineers