Glass transition temperature of starches with different amylose/amylopectin ratios

Changes in the pasting and rheological properties of wheat, corn, water caltrop and lotus rhizome starches by the addition of Annona montana mucilage

Annona montana mucilage (AMM) is a novel mucilage with unique but limited information. This study investigated the effects of AMM addition on the pasting and rheological properties of wheat starch (WS), corn starch (CS), water caltrop starch (WCS), and lotus rhizome starch (LRS). The addition of AMM generally increased the pasting temperature and peak viscosity, but reduced the setback value of all starches to varying degrees, and the initiation of viscosity-increase for cereal starch/AMM systems during pasting occurred at lower temperatures, accompanied with a distinctive two-stage swelling process as well as lower peak and final hot paste viscosity at 50 °C. AMM significantly increased the pseudoplasticity and entanglement of the systems to varying degrees (LRS > WS > WCS > CS). Under a constant shear rate of 50 s-1, the consistency level was found to fall in honey-like for cereal starch/AMM groups, and honey-like to extremely thick levels for WCS and LRS/AMM groups. Except for the WCS/AMM systems, the storage and loss modulus as well as tan increased with increasing AMM concentration. Short-term retrogradation of starch at 4 °C was pronouncedly retarded by the addition of AMM for WS, CS and WCS groups, but was less affected for LRS group.

Evaluation of Starch-Garlic Husk Polymeric Composites through Mechanical, Thermal, and Thermo-Mechanical Tests

The present work evaluates the influence of different properties of composite materials from natural sources. Films were prepared using the evaporative casting technique from corn starch reinforced with a waste material such as garlic husk (GH), using glycerin as a plasticizer. The results of the syntheses carried out demonstrated the synergy between these materials. In the morphological analysis, the compatibility and adequate dispersion of the reinforcer in the matrix were confirmed. Using Fourier transform infrared spectroscopy (FTIR), the interaction and formation of bonds between the matrix and the reinforcer were confirmed by the presence of some signals such as S-S and C-S. Similarly, thermogravimetric analysis (TGA) revealed that even at low concentrations, GH can slightly increase the decomposition temperature. Finally, from the results of dynamic mechanical analysis (DMA), it was possible to identify that the storage modulus increases significantly, up to 115%, compared to pure starch, especially at low concentrations of the reinforcer.

Physicochemical, thermal, pasting, morphological, functional and bioactive binding characteristics of starches of different oat varieties of North-Western Himalayas

Starches were isolated from five oat varieties (SFO-1, SFO-3, Sabzar, SKO-20 and SKO-96) grown in North-Western Himalayas of India. Moisture content of the varieties ranged from 9.25 ± 0.09 to 13.21 ± 0.11 %, indicating their shelf-stability. Results suggested >90 % purity of starches as was evident from values of ash, proteins, and lipids. Amylose content results showed that all starches fall within category of intermediate-amylose starches. Lambdamax, blue value and OD620/550 were found significantly (p ≤ 0.05) higher in SKO-20. Sabzar exhibited higher starch hydrolysis percentage of 85.16 % whereas, lowest was observed in SKO-20 (78.12 %). Degree of syneresis was higher in SKO-20 however, its freeze-thaw stability was lesser. Wide peak in FTIR spectra at 3320 cm-1 confirms nature of starches. SKO-20 exhibited significantly higher onset gelatinization temperature (65.19 ± 1.06 °C) and enthalpy (15.78 ± 0.15 J/g) whereas, Sabzar exhibited lowest enthalpy. Pasting characteristics indicated lowest and highest final viscosity in SKO-20 (341.30 ± 2.11 mPas) and SKO-96 (1470 ± 4.56 mPas), respectively. SEM results indicated irregular and polygonal shape of starches with size <10 μm. SKO-20 exhibited lowest disintegration time of 2.08 ± 0.01 min and Sabzar showed highest (3.31 ± 0.07 min). SKO-20 released more curcumin (71.28 %) whereas, Sabzar released less. This suggests that SKO-20 could be used as better excipient for delivery of curcumin at target site.

Thermoplastic Starch Biocomposite Films Reinforced with Nanocellulose from Agave tequilana Weber var. Azul Bagasse

In this work, cellulose nanocrystals (CNCs), bleached cellulose nanofibers (bCNFs), and unbleached cellulose nanofibers (ubCNFs) isolated by acid hydrolysis from Agave tequilana Weber var. Azul bagasse, an agro-waste from the tequila industry, were used as reinforcements in a thermoplastic starch matrix to obtain environmentally friendly materials that can substitute contaminant polymers. A robust characterization of starting materials and biocomposites was carried out. Biocomposite mechanical, thermal, and antibacterial properties were evaluated, as well as color, crystallinity, morphology, rugosity, lateral texture, electrical conductivity, chemical identity, solubility, and water vapor permeability. Pulp fibers and nanocelluloses were analyzed via SEM, TEM, and AFM. The water vapor permeability (WVP) decreased by up to 20.69% with the presence of CNCs. The solubility decreases with the presence of CNFs and CNCs. The addition of CNCs and CNFs increased the tensile strength and Young's modulus and decreased the elongation at break. Biocomposites prepared with ubCNF showed the best tensile mechanical properties due to a better adhesion with the matrix. Images of bCNF-based biocomposites demonstrated that bCNFs are good reinforcing agents as the fibers were dispersed within the starch film and embedded within the matrix. Roughness increased with CNF content and decreased with CNC content. Films with CNCs did not show bacterial growth for Staphylococcus aureus and Escherichia coli. This study offers a new theoretical basis since it demonstrates that different proportions of bleached or unbleached nanofibers and nanocrystals can improve the properties of starch films.

Adhesive and Flame-Retardant Properties of Starch/Ca2+ Gels with Different Amylose Contents

Starch, being renewable and biodegradable, is a viable resource for developing sustainable and environmentally friendly materials. The potential of starch/Ca2+ gels based on waxy corn starch (WCS), normal corn starch (NCS), and two high-amylose corn starches, G50 (55% amylose content) and G70 (68% amylose content) as flame-retardant adhesives has been explored. Being stored at 57% relative humidity (RH) for up to 30 days, the G50/Ca2+ and G70/Ca2+ gels were stable without water absorption or retrogradation. The starch gels with increasing amylose content displayed increased cohesion, as reflected by significantly higher tensile strength and fracture energy. All the four starch-based gels showed good adhesive properties on corrugated paper. For wooden boards, because of the slow diffusion of the gels, the adhesive abilities are weak initially but improve with storage extension. After storage, the adhesive abilities of the starch-based gels are essentially unchanged except for G70/Ca2+, which peels from a wood surface. Moreover, all the starch/Ca2+ gels exhibited excellent flame retardancy with limiting oxygen index (LOI) values all around 60. A facile method for the preparation of starch-based flame-retardant adhesives simply by gelating starch with a CaCl2 solution, which can be used in paper or wood products, has been demonstrated.

Generation of Sulfonated Lignin-Starch Polymer and Its Use As a Flocculant

This paper reports the polymerization of tall oil lignin (TOL), starch, and 2-methyl-2-propene-1-sulfonic acid sodium salt (MPSA), a sulfonate-containing monomer, in a three-component system to generate flocculants for colloidal systems. By utilizing the advanced 1H, COSY, HSQC, HSQC-TOCSY, and HMBC NMR techniques, it was confirmed that the phenolic substructures of TOL and the anhydroglucose unit of starch were covalently polymerized by the monomer to generate the three-block copolymer. The molecular weight, radius of gyration, and shape factor of the copolymers were fundamentally correlated to the structure of lignin and starch, as well as the polymerization outcomes. The deposition behavior of the copolymer, studied by a quartz crystal microbalance with dissipation (QCM-D) analysis, revealed that the copolymer with a larger molecular weight (ALS-5) deposited more and generated more compact adlayer than the copolymer with a smaller molecular weight on a solid surface. Owing to its higher charge density, molecular weight, and extended coil-like structure, ALS-5 produced larger flocs with faster sedimentation in the colloidal systems, regardless of the extent of agitation and gravitational force. The results of this work provide a new approach to preparing a lignin-starch polymer, i.e., a sustainable biomacromolecule with excellent flocculation performance in colloidal systems.

Temperature responsive crosslinked starch-kraft lignin macromolecule

Starch is a natural polymer with a relatively simple structure and limited solubility in water. Kraft lignin (KL) is a complex biopolymer obtained as a by-product from the delignification of wood and grasses. The present work reports developing a temperature-responsive high molecular weight macromolecule from crosslinking KL and starch (KLS). The NMR and XPS analyses quantified the changes in the aromatic and anhydroglucose units of KL and starch, observing a higher content of C-O-C bonds, which confirms the presence of glycerol ether cross-linkages between starch and KL in KLS. The rheological analysis of KLS dispersions revealed the formation of a thermo-responsive structured network. The temperature-dependent water solubility and rheological characteristics of KLS were related to the presence of hydrophilic starch chains, crosslinking degree, and physicochemical characteristics of KL. The incorporation of KL and ether crosslinks increased the thermal stability of KLS. Because of its multiple functional groups and large molecular weight (3.6-4.2 × 10⁵ g/mol) that was arranged in an extended globular shape, KLS-5 formed a gel-like structure after a heating-cooling treatment. Overall, the results confirmed that incorporating lignin in starch would fabricate sustainable materials with potentially altered applications, such as temperature-responsive hydrogels and films.

Insights on Some Polysaccharide Gel Type Materials and Their Structural Peculiarities

Global resources have to be used in responsible ways to ensure the world's future need for advanced materials. Ecologically friendly functional materials based on biopolymers can be successfully obtained from renewable resources, and the most prominent example is cellulose, the well-known most abundant polysaccharide which is usually isolated from highly available biomass (wood and wooden waste, annual plants, cotton, etc.). Many other polysaccharides originating from various natural resources (plants, insects, algae, bacteria) proved to be valuable and versatile starting biopolymers for a wide array of materials with tunable properties, able to respond to different societal demands. Polysaccharides properties vary depending on various factors (origin, harvesting, storage and transportation, strategy of further modification), but they can be processed into materials with high added value, as in the case of gels. Modern approaches have been employed to prepare (e.g., the use of ionic liquids as "green solvents") and characterize (NMR and FTIR spectroscopy, X ray diffraction spectrometry, DSC, electronic and atomic force microscopy, optical rotation, circular dichroism, rheological investigations, computer modelling and optimization) polysaccharide gels. In the present paper, some of the most widely used polysaccharide gels will be briefly reviewed with emphasis on their structural peculiarities under various conditions.

Increasing agar content improves the sol-gel and mechanical features of starch/agar binary system

Starch/agar systems are highly potential for versatile applications such as packaging and biomedical materials. Here, how combined factors affect the features of a starch/agar binary system were explored. An increase of starch amylose/amylopectin ratio from 0/100 to 50/50 increased the sol-gel transition temperature and gel hardness of the aqueous starch/agar mixture. An increased agar content (mainly from 30% to 70%) allowed increases in both the tensile strength (reaching 50-60 MPa) and elongation at break of the starch/agar binary films. This phenomenon should be related to the strengthened crystalline structure and the weakened hydrogen bonding between starch chains (reflected by infrared spectroscopy). Furthermore, a higher relative humidity (from 30% to 70%) allowed enhanced chain interactions and probably nanoscale molecular order but weakened the crystalline structure, leading to reduced tensile strength and increased elongation at break. This work could facilitate the design of starch/agar binary systems with improved sol-gel and mechanical performance.

Applications of waxy corn flour based on physicochemical and processing properties: comparison with waxy rice flour and waxy corn starch

The proximate composition, molecular weight distribution and main processing properties of waxy corn flour (WCF) were investigated. Furthermore, waxy corn starch (WCS) and waxy rice flour (WRF) were also determined to discuss the applications of WCF. WCS contained more low-molecular-weight fraction (<5 × 105 g/mol) and had higher polydispesity than waxy rice starch (WRS). The water hydration capacity of WCF was the lowest, whereas it had the highest swelling power at 70 and 80 °C. WCF had the highest pasting temperature of 74.85 °C, whereas that of WRF was 68.40 °C and WCS was 73.25 °C. WRF exhibited the lowest melting enthalpy change with a value of 2.54 ± 0.11 (J/g). The retrogradation resistance of WCF was better than that of WRF and WCS. The degree of retrogradation (DR) of WCF was 9.58 ± 0.59% at 14 d, corresponding to WCS of 25.08 ± 0.44% and WRF of 15.68 ± 0.71%. WRF had the lowest glass transition temperature of −27.4 versus −26.2 °C for WCF and −26.0 °C for WCS. It was found that WCF could be used to directly prepare quick-frozen viscous foods. It could also be used as a stabilizer to improve the quality of staple foods.

Modern Biodegradable Plastics-Processing and Properties: Part I

This paper presents a characterization of a plastic extrusion process and the selected properties of three biodegradable plastic types, in comparison with LDPE (low-density polyethylene). The four plastics include: LDPE, commercial name Malen E FABS 23-D022; potato starch based plastic (TPS-P), BIOPLAST GF 106/02; corn starch based plastic (TPS-C), BioComp®BF 01HP; and a polylactic acid (polylactide) plastic (PLA), BioComp®BF 7210. Plastic films with determined geometric parameters (thickness of the foil layer and width of the flattened foil sleeve) were produced from these materials (at individually defined processing temperatures), using blown film extrusion, by applying different extrusion screw speeds. The produced plastic films were tested to determine the geometrical features, MFR (melt flow rate), blow-up ratio, draw down ratio, mass flow rate, and exit velocity. The tests were complemented by thermogravimetry, differential scanning calorimetry, and chemical structure analysis. It was found that the biodegradable films were extruded at higher rate and mass flow rate than LDPE; the lowest thermal stability was ascertained for the film samples extruded from TPS-C and TPS-P, and that all tested biodegradable plastics contained polyethylene.

Effect of type and amount of modified corn starches on qualitative properties of low-protein biscuits for phenylketonuria

The effect of corn starches (natural, pregelatinized, and cross-linked) in four levels on quality of low-protein biscuit was evaluated. First, the microscopic structure, thermal properties, and low-branched chains content of them were evaluated. Water absorption capacity (WAC) and gelatinization properties of combined starches and physicochemical properties of products were assessed. Cross-linked starch had the highest glass transition temperature (Tg ). The maximum and minimum WAC was observed in samples containing 100% pregelatinized and 100% cross-linked starches, respectively. An increase in the amount of pregelatinized starch was accompanied by a decrease in the maximum viscosity and gelatinization temperature. Pregelatinized starch improved sensory and textural characteristics of samples, while cross-linked starch affected baking properties of the product. The best sample containing 30% of pregelatinized and 70% cross-linked starch with 1.27 g protein and 12 mg phenylalanine in 100 g biscuit is introduced as the low protein and safe product for Phenylketonuria.

Gelatinization dynamics of starch in dependence of its lamellar structure, crystalline polymorphs and amylose content

Structural dynamics of starch granules selected for different amylose content and crystalline type were analysed in excess water upon heating observed in-situ using SAXS and WAXS. The results showed that NMS and MBS exhibited higher degree of lamellar order than HAM. The peak width at half-maximum (FWHM) of HAM and NMS increased with temperature, demonstrating a gradual radial swelling of the lamellae during gelatinization. For NMS and HAM FWHM increased, suggesting that the dynamics of lamellar thicknesses of these starches were increased during hydrothermal compression exerted by the amorphous lamella. The decrease in FWHM found for MBS indicates that these lamellae were very vulnerable for dissolution. The changes in SAXS peak areas found for NMS and MBS were different from the areas of HAM indicating that A-type starch, as compared to B-type starch, possesses higher degree of lamellae ordering. Our data are potentially useful in starch-based materials processing.

Microwave treatment regulates the free volume of rice starch

The aim of this work was to investigate the role of microwave parameters and moisture content on the free volume (FV) changes of rice starch by positron annihilation lifetime spectroscopy analysis (PALS) and to explore the potential relationship between the changes of FV and physicochemical properties of rice starch. Microwave heating and water molecules lead to the increasing of FV of starch. However, this result is largely influenced by the plasticization of water molecule. The anti-plasticization caused by water evaporation resulting in a decrease in the size and concentration of FV during microwave heating. Significant decrease (p < 0.05) in the thickness of amorphous region of microwave-heated rice starch was found by small angle X-ray scattering (SAXS), and the glass transition temperature (Tg) and gelatinization temperature significantly increase (p < 0.05) after microwave heating. According to correlation analysis, the power intensity and heating time were correlated negatively with the lifetime of o-Ps. In addition, the changes of amorphous region and Tg of rice starch were strongly related to FV changes. These results provided a theoretical basis for further research on the directional regulation of FV and improvement the quality of starch-based food by using microwave treatment.

Cationic starch/pDNA nanocomplexes assembly and their nanostructure changes on gene transfection efficiency

This study aims at developing biocompatible starch based gene carriers with good gene delivery and transfection efficacy. By controlling the molecular weight and aggregation behavior of spermine modified cationic starch (CS) molecules, nanocomplexes spontaneously formed through electrostatic interaction using CS and plasmid pAcGFP1-C1 (pDNA) displaying different structural changes (particle size, zeta potential, shape, compactness) response to the simulated intracellular pH variation. Results indicated that CS2 with weight average molecular weight (Mw) of 6.337 × 10⁴ g/mol displayed relatively higher transfection efficacy (~30%) in HepG2 cells than others and revealed significantly low cytotoxicity. By simulating the intracellular pH variation, Dynamic Light Scattering (DLS) and Small Angle X-ray Scattering (SAXS) results demonstrated that CS2 could bind to pDNA tightly and form nanocomplexes with smaller and compact internal aggregate structure at acidic conditions, which facilitated the effective pDNA protection under endosome pH change, while larger and loose internal aggregate structure at physiological pH which promoted the disintegration of CS2/pDNA nanocomplexes. Therefore, CS with suitable Mw of around 6.0 × 10⁴ g/mol represents a potential gene carrier for gene delivery. This study also demonstrated that controlling the internal nanostructure change of polymer/gene nanocomplexes could provide guidance in designing effective starch based gene carriers.

Mechanical and barrier properties of maize starch-gelatin composite films: effects of amylose content

BACKGROUND

In order to obtain new reinforcing bio-fillers to improve the physicochemical properties of gelatin-based films, three types of maize starch, waxy maize starch (Ap), normal starch (Ns) and high-amylose starch (Al), were incorporated into gelatin film and the resulting film properties were investigated, focusing on the impact of amylose content.

RESULTS

The thickness, opacity and roughness of gelatin film increased depending on the amylose content along with the starch concentration. The effects of the three starches on the mechanical properties of gelatin film were governed by amylose content, starch concentration as well as environmental relative humidity (RH). At 75% RH, the presence of Al and Ns in the gelatin matrix increased the film strength but decreased its elongation, while Ap exhibited an inverse effect. Starch addition decreased the oxygen permeability of the film, with the lowest value at 20% Al and Ns. All starches, notably at 30% content, led to a decrease in the water vapor permeability of the film at 90% RH, especially Ns starch. Furthermore, the starches improved the thermal stability of the film to some extent. Fourier transform infrared spectra indicated that some weak intermolecular interactions such as hydrogen bonding occurred between gelatin and starch. Moreover, a high degree of B-type crystallinity of starch was characterized in Gel-Al film by X-ray diffraction.

CONCLUSION

Tailoring the properties of gelatin film by the incorporation of different types of maize starch provides the potential to extend its applications in edible food packaging. © 2017 Society of Chemical Industry.

Methods to characterize the structure of food powders – a review

Food powders can exist in amorphous, crystalline or mixed structure depending on the order of molecular arrangement in the powder particle matrices. In food production, the structure of powders has a greatly effect on their stability, functionality, and applicability. The undesirable structure of powders can be accidentally formed during production. Therefore, characterization of powder structure as well as quantification of amorphous–crystalline proportions presenting in the powders are essential to control the quality of products during storage and further processing. For these purposes, many analytical techniques with large differences in the degree of selectivity and sensitivity have been developed. In this review, differences in the structure of food powders are described with a focus being placed on applications of amorphous powders. Essentially, applicability of common analytical techniques including X-ray, microscopic, vapor adsorption, thermal, and spectroscopic approaches for quantitative and qualitative structural characterization of food powders is also discussed.