Range Molecular Order Research Articles

Effects of moisture content on digestible fragments and molecular structures of high amylose jackfruit starch prepared by improved extrusion cooking technology

The effects of different moisture contents on the digestible fragments and molecular structures of high amylose jackfruit starch were investigated. The digestible fragments and molecular structures of rapidly digestible starch, slowly digestible starch and resistant starch of high amylose jackfruit starch with different moisture contents prepared by improved extrusion cooking technology were analyzed. Decreasing the moisture content resulted in significant decrease in slowly digestible starch and resistant starch content (24.08% and 25.99%–17.59% and 16.60%), indicating that high amylose jackfruit starch with low moisture content was easier to digest. Compared to extruded control starches, the slowly digestible starch + resistant starch fraction and resistant starch samples exhibited higher gelatinization enthalpy, relative crystallinity, and short - range molecular order, but no significant difference was showed in gelatinization temperature. It was also found that the double helix degree, crystallinity and order degree of the extruded controls, slowly digestible starch + resistant starch fractions and resistant starch samples were increased with increasing moisture content, from 1.74 J/g, 1.52% and 0.207–9.52 J/g, 32.54% and 0.779, respectively. The above results were further supported by the microstructural and porosity analysis that the extruded samples were changed from coarser surface structure to more compact structure with increasing moisture content. All these results indicate that moisture content affects the digestible fragments and molecular structures of starch. Therefore, it can provide a theoretical basis for the modification of high amylose starch, especially for the modification of resistant starch. • High amylose jackfruit starch (HA-JFSS) were prepared by improved extrusion cooking technology. • Different moistures content affected the digestible fragment and molecular structure of HA-JFSS. • Decreasing moisture content improved the in vitro digestibility of extruded HA-JFSS. • High moisture content HA-JFSS showed higher double helix, long/short-range molecular order. • The analysis of SEM demonstrated the results of the DSC, XRD and FITR.

Understanding the native and hydrothermally modified elephant foot yam (Amorphophallus paeoniifolius) starch system: A multivariate approach

Consumption of highly digestible native starch is considered to be detrimental for diabetes and obese patients. To address this issue, starch extracted from elephant foot yam was subjected to the heat moisture treatment (HMT) using various heating sources i.e. hot air oven (HAO), microwave (MW), and autoclave (AL). The research focuses on the key characteristics and relationships between various functionalities and digestion parameters of the starch system, which substantially effects the formulation of the low digestible food products. The First-order kinetic model was employed to understand the digestion kinetics of native and modified elephant foot yam starch (EFYS). The multivariate analysis highlighted the significant effect of amylose and short range molecular order (R1047/1022) on the formation of resistant starch content. Principal component analysis (PCA) and Pearson's correlation coefficient revealed solubility as the crucial parameter for altering the rapidly digestible starch fractions. Hierarchical cluster analysis (HCA) showed a similar treatment effect of AL and MW, whereas HAO modification had the greatest influence on EFYS. Compared to other treated EFYS, HAO modified EFYS containsthe lowest glycemic index, making it ideal for forming diabetic-friendly food products.

Structural Features Guiding the Design of Liquid-Crystalline Elastomeric Fluorescent Force Sensors

Liquid single crystal elastomers (LSCEs) containing carbazole fluorogenic components alter their luminescence when they are stretched along the director direction. The differential luminescent behavior arises from the distinct interaction between the carbazole fluorophores and their local environment before and after the application of the mechanical input. Indeed, the uniaxial deformation of the material, along its anisotropic direction, forces a closer mesogen–fluorophore interaction, which leads to the quenching of the carbazole luminescence. Importantly, this intermolecular interaction is intimately related to the intrinsic order present in the LSCE. As a result, the amount of light emitted by the material in the form of fluorescence diminishes upon deformation. Thus, the application of mechanical stimuli to liquid-crystalline elastomers furnishes to two interconvertible states for the system with distinct optical properties (with either different emission color or fluorescence intensity). The initial state of the material is completely restored once the applied force is removed. In this way, this kind of macromolecular system can transduce mechanical events into detectable and processable optical signals, thus, having great potential as optical force sensors. In this context, the realization of the distinct structural factors that govern the interactions established between the mesogenic and fluorogenic units at the supramolecular level upon deformation is essential for the development of efficient LSCE-based force sensors. In fact, not only the density of carbazole units and their connection to the main polymer backbone, but also the presence of long range molecular order in the system and the type of mesophase exhibited by the LSCE are key factors for the conception of efficient force sensors based on these self-organized polymer networks. In this review, we present a comprehensive and systematic description of the different features that control the mechanoluminescent behavior of fluorescent liquid-crystalline elastomers and will guide the future design of LSCE-based force sensors with improved performances.

Protein-directed crystalline 2D fullerene assemblies.

Water soluble 2D crystalline monolayers of fullerenes grow on planar assemblies of engineered consensus tetratricopeptide repeat proteins. Designed fullerene-coordinating tyrosine clamps on the protein introduce specific fullerene binding sites, which facilitate fullerene nucleation. Through reciprocal interactions between the components, the hybrid material assembles into two-dimensional 2 nm thick structures with crystalline order, that conduct photo-generated charges. Thus, the protein-fullerene hybrid material is a demonstration of the developments toward functional materials with protein-based precision control of functional elements.

Routes to singlet exciton fission in rubrene crystals and amorphous films

By using wavelength-tunable, low fluence picosecond pulses at a 1 kHz repetition rate in a transient grating pump and probe configuration, we show that photoexcitation to higher vibrational levels leads to slower singlet exciton fission rates in rubrene. After the 1 ps photoexcitation, the initial growth of the triplet exciton population is exponential, with its time-constant systematically varying from 2.5 ± 0.7 ps to 40 ± 15 ps as the excitation photon energy is increased from the lowest to the third main vibrational band in the vibrational progression of rubrene’s absorption spectrum. We also determine that short-pulse-induced fluorescence in amorphous rubrene films deposited by molecular beam epitaxy in high vacuum decays as a single exponential with a lifetime of 15.2 ns, close to rubrene’s radiative lifetime for molecules in solution. This shows that singlet fission is non-existent in fully amorphous rubrene films, despite the close molecular packing, which indicates that in these films there is no short range molecular order matching the molecular arrangement in orthorhombic rubrene crystals.

In vitro digestibility and physicochemical properties of milled rice

Rice is a staple diet as well as a major ingredient in many processed foods. The physicochemical and supra-molecular structure of eight rice varieties with amylose content from 9% to 19% were studied to elucidate the factors responsible for variation in enzymatic digestibility of raw and cooked rice. Parboiled rice had a digestion rate coefficient almost 4.5 times higher than the least digestible Low GI rice. The rate coefficient was found to be independent of helical structure and long range molecular order, possibly attributed to the effect of rice flour architecture. Strong swelling and pasting behaviour and lower gelatinisation temperature were linked with apparently higher in vitro digestibility but the relationship was statistically insignificant. It is concluded that the enzymatic susceptibility of rice flours are independent of supra-molecular structure and are most likely controlled by external factors not limited to particle size, presence of intact cell wall and other non-starch polymers.

Preparation and characterization of gelatinized granular starches from aqueous ethanol treatments

In order to modify the properties of native starch granules, the formation of gelatinized granular forms (GGS) from normal, waxy, and high amylose maize, as well as potato and tapioca starches was investigated by treating granules with aqueous ethanol at varying starch:water:ethanol ratios and then heating in a rotary evaporator to remove ethanol. The modified starches were characterized using bright field, polarized and electron microscopy. Short/long range molecular order and enthalpic transitions on heating were also studied using infrared spectroscopy, X-ray diffractometry and differential scanning calorimetry respectively. A diffuse birefringence pattern without Maltese cross was observed for most GGS samples. Treatment with aqueous ethanol resulted in starch-specific changes in the surface of granules, most noticeably swelling and disintegration in waxy maize, surface wrinkling in normal maize and tapioca, swelling and opening-up in potato starches, and swelling and bursting in high amylose maize. The ratio of ethanol to water at which original granular order was disrupted also varied with starch type. GGS had less short range molecular order than native granules as inferred by comparing 1047/1022 wave number ratio from infrared spectroscopy. Similarly, A- and B-type diffraction reflections were either reduced or completely lost with evolution of V-type patterns in GGS.

Carrier transport simulation in a model liquid crystalline system with the biaxial Gay–Berne potential

In this paper, we performed carrier transport simulation to understand the unusual temperature dependence of the carrier mobility observed in nematic liquid crystals. For this purpose, we made a model liquid crystalline system consisting of biaxial Gay-Berne particles, and then we simulated hopping transport between these particles. The hopping rate was formulated suitably for the biaxial Gay-Berne particles based on the investigation of the electronic overlaps between actual aromatic molecules. The carrier transport simulation was performed by master equation method on the model system prepared by N-P-T ensemble Monte Carlo simulation. We reproduced gradual mobility increase in the nematic phase as a result of the change in the short range molecular order.

Enzyme resistance and structural organization in extruded high amylose maize starch

Gelose 80, a high amylose maize starch, was extruded in a twin screw extruder at different feed moistures, cooled, stored for 12 days at 4 °C, and cryo-milled. The raw and extruded starches were analysed for in vitro enzyme-resistant starch content (ERS), morphology, in vitro digestibility, long range (X-ray diffraction) and short range (FTIR) molecular order. Extrusion markedly increased the rate of starch digestion and reduced the ERS content, irrespective of whether B-type or B- and V-type polymorphs were present. Increasing feed moisture and storage resulted in only slight increases in ERS content, with X-ray diffraction and FTIR also showing small changes in long and short range molecular order, respectively. Analysis of residues from in vitro digestion showed the mechanism of enzyme resistance of granular and extruded high amylose starch to be markedly different, both qualitatively and quantitatively. Enzyme digestion of granular high amylose maize starch showed initial disorganization in structure followed by slow reorganization at later stages of digestion. In contrast, molecular reorganization took place throughout the enzyme digestion of extruded high amylose maize starch. Higher levels of crystallinity were found in digested extrudates compared with digested granules, showing that there is no direct correlation between starch crystallinity and enzyme digestion rates.

Isotactic polystyrene/cis-decaline mixtures: phase diagram and molecular structures

Organized structures grown from iPS/cis-decalin solutions (ranging from 5% to 50% w/w) have been studied by several techniques. From DSC experiments the thermal behavior has been investigated as a function of the annealing temperature. The temperature-concentration phase diagram has been established. From neutron diffraction experiments the short range molecular order has been determined. We show that between the gel state formed at high undercooling and the crystalline state obtained at low undercooling there exist two intermediate phases: thes-phase, already described by Klein et al., and thep-phase. Except for the crystalline state all the other phases contain intercalated solvent molecules. Thegel state displays nematic-like order, whereas thes-phase is reminiscent of smectic arrangements. Thep-phase is less solvated and can be described as a peritectic system. Preliminary neutron scattering experiments show that chain-folding reappears in thes-phase, whereas it was shown to be absent in thegel phase.

Molecular complexes. Part 10.—Theory for complex formation and nuclear magnetic resonance evidence for short range molecular order in liquids

For reactions of the type A + B ⇌ AB occurring in the presence of an inert solvent, S, it is shown that the aromatic induced n.m.r. chemical shift, Δc, varies with the composition of the mixtures studied in a similar fashion to the equilibrium quotient, Kx. This is explained in terms of a model based on short range order in liquids, which allows aromatic molecules, B, to be preferentially attracted to the solute, A, in the form of solvation shells; experimental and theoretical justification of this is given. The cage model used to describe the formation of bimolecular complexes requires that a polar solute (A) exchanges rapidly between a limiting number of aromatic molecules in the solvation shells, which in turn exchange with molecules in the surrounding medium. The model is used to explain the variation in observed shifts caused by complex formation.

Long range molecular order in polyethylene

Long range molecular order in polyethylene