Interaction between dry starch and plasticisers glycerol or ethylene glycol, measured by differential scanning calorimetry and solid state NMR spectroscopy

Synthesis and Characterization of Triticale Starch-Based Hydrogel for pH Responsive Controlled Diffusion

Considering the FAO perspectives for agriculture toward 2030, many natural sources will be no longer profitable for the synthesis of many biomaterials. Triticale (X Triticosecale Wittmack) is a cereal crop synthesized to withstand those marginal conditions; however, it is primarily used as fodder worldwide. We reported for the first time the synthesis of a natural anionic hydrogel with gastrointestinal pH stimulus-response as a new alternative of smart material, based on Eronga triticale starch as sustainable biomass, using citrate (pK a ∼3.1, 4.7, and 6.4) as cross-linking agent. The scanning electron microscopy and X-ray diffraction exhibited A and B-type starch granules, and semicrystallinity A-type. The presence of the anionic sensing group (COOH) was verified by infrared spectroscopy, the interactions by hydrogen bonds between starch and glycerol and esterification between starch and citric acid were identified by 1H NMR spectra, and through thermal analysis hydrogels exhibited four endothermic curves (179-319 °C, ∼0.711-39 kJ/mol E a). The results showed that the slight addition of glycerol increases the thermal stability, but a higher amount of glycerol decreases the intermolecular forces affecting the thermal stability contrary, the mechanical properties could be benefited. The rheological analyses showed viscoelastic tendency (G' > G″) with high stability (Tanδ < 1) in frequency, time, and strain sweeps. Gastrointestinal pH sensitivity (∼2-7.8) was verified (α ≤ 0.01) following Fick's diffusive parameters, which resulted in a tendency to gradually release BSA with increasing pH ∼3-7 by anomalous and case-II diffusion, showing greater release at pH ∼7.8/3.5 h (80-96%). We aim to expand the biomaterials area focusing on triticale starch due to its limited reported investigations, low-cost, green modification, and its rheological performance as plastic.

Bionanocomposite Based on Cassava Waste Starch, Locust Bean Galactomannan, and Cassava Waste Cellulose Nanofibers

Natural polysaccharides are among the renewable sources with great potential for replacing petroleum-derived chemicals as precursors to produce biodegradable films. This study aimed to prepare biopolymeric films using starch extracted from the periderm and cortex of cassava roots (waste from cassava root processing), locust bean galactomannan, and cellulose nanofibers also obtained from cassava waste. The films were prepared by casting, and their physicochemical, mechanical, and biodegradability properties were evaluated. The content of cellulose nanofibers varied from 0.5 to 2.5%. Although the addition of cellulose nanofibers did not alter the mechanical properties of the films, it significantly enhanced the vapor barrier of the films (0.055 g mm/m2 h kPa-2.5% nanofibers) and their respective stabilities in aqueous acidic and alkaline media. All prepared films were biodegradable, with complete degradation occurring within five days. The prepared films were deemed promising alternatives for minimizing environmental impacts caused by the disposal of petroleum-derived materials.

A Preliminary Study on the Release of Bioactive Compounds from Rice Starch Hydrogels Produced by High-Pressure Processing (HPP)

This work aimed to carry out a preliminary study on the release of bioactive compounds loaded into starch-based hydrogels produced by high-pressure processing (HPP). As a study case, the experiments were carried out on rice starch HPP hydrogels. Rice starch (20% w/w) and green tea extract (2% w/w), suspended in distilled water, were treated by HPP at processing conditions enabling starch gelatinisation, namely 600 MPa for 15 min at room temperature. Additional experiments were carried out on samples that were further loaded with glycerol (5% w/w). Gel formation was assessed by analysing the gelatinisation extent, structuring level, and swelling power of the samples. At the processing conditions utilised, stable hydrogels were obtained even in the presence of the extract and/or the glycerol in the starch suspension. As expected, the colour of the hydrogels formed was affected by the addition of green tea extract in the starch solution. HPP starch hydrogels were characterised by Fourier transform infrared spectroscopy (FT-IR) to determine the interactions between the different compounds utilised in the formulation. Moreover, the release kinetics of bioactive compounds from HPP rice starch hydrogels was evaluated using a vertical Franz diffusion cells system, simulating a transdermal pattern. The diffusion of bioactive compounds was measured spectrophotometrically and via HPLC analysis. A controlled release of bioactive compounds from the hydrogel structure was detected, suggesting that small molecules, such as polyphenols, positively interacted with the rice starch HPP hydrogel network that allowed a smooth and constant release of these bioactive compounds over time.

Effect of branched polyethyleneimine and citric acid on the structural, physical and antibacterial properties of corn starch/chitosan films

To improve the antibacterial and physical properties of corn starch/chitosan films effectively, starch/chitosan/polyethyleneimine (PEI) blend films crosslinked by citric acid (labeled SCPC) with different contents (2.5 %, 5.0 %, 7.5 % and 10.0 %) were prepared by the solution casting method. The films were characterized in detail. The results showed that the addition of 3.75 % PEI improved the tensile strength and elongation at break of the starch/chitosan film simultaneously, but the thermal stability decreased. After CA was incorporated, the tensile strength and thermal stability of the films were enhanced significantly. FTIR, XRD, and ¹H NMR analyses revealed strong interactions among CA, PEI and starch-chitosan. All films showed smooth and homogenous fragile cross-sections. The water vapor permeability of the film decreased overall after PEI and CA addition. Moisture uptake (MU) accelerated after PEI addition, but the balanced MU was reduced by CA cross-linking. All films showed an inhibitory effect on E. coli and S. aureus, and CA incorporation significantly improved the inhibition ability of the film. The SCPC film with 3.75 % PEI and 5.0 % CA addition has the best comprehensive properties, which endowed its application in the bioactive packaging field.

Structure of Starch-Sepiolite Bio-Nanocomposites: Effect of Processing and Matrix-Filler Interactions

Sepiolite clay is a natural filler particularly suitable to be used with polysaccharide matrices (e.g., in starch-based bio-nanocomposites), increasing their attractiveness for a wide range of applications, such as packaging. Herein, the effect of the processing (i.e., starch gelatinization, addition of glycerol as plasticizer, casting to obtain films) and of the sepiolite filler amount on the microstructure of starch-based nanocomposites was investigated by SS-NMR (solid-state nuclear magnetic resonance), XRD (X-ray diffraction) and FTIR (Fourier-transform infrared) spectroscopy. Morphology, transparency and thermal stability were then assessed by SEM (scanning electron microscope), TGA (thermogravimetric analysis) and UV-visible spectroscopy. It was demonstrated that the processing method allowed to disrupt the rigid lattice structure of semicrystalline starch and thus obtain amorphous flexible films, with high transparency and good thermal resistance. Moreover, the microstructure of the bio-nanocomposites was found to intrinsically depend on complex interactions among sepiolite, glycerol and starch chains, which are also supposed to affect the final properties of the starch-sepiolite composite materials.

Enhancement of mechanical and thermal properties of Ixora coccinea L. plant root derived nanocellulose using polyethylene glycol-glutaraldehyde system

Nanocellulose fibers are widely acknowledged as a more sustainable alternative to polyimide and polyethylene terephthalate-based plastic films derived from petrochemicals. Cellulose is also utilised in packaging, tissue engineering, electronic, optical, and sensor applications, pharmaceutical applications, cosmetic applications, insulation, water filtration, and hygiene applications, as well as vascular grafts. In the present study to improve the tensile and thermal properties of cellulose nanofibers, polyethylene glycol (PEG 600) with varying concentrations was produced by solvent casting and chemically crosslinked with glutaraldehyde (GA). The effects of various PEG 600 concentrations on nanofibers and the morphology of the resulting nanofibers were investigated. The effects of GA on PEG-nanocellulose morphology, average diameter, tensile strength, elongation, and thermal characteristics were investigated. Strong (GA)-based acetal linkages are used to substitute secondary hydrogen bonds in nanocellulose films. The 1% PEG 600 plasticized nanocellulose scaffolds cross-linked with GA showed a higher tensile modulus (93 MPa) than its GA untreated nanocellulose scaffolds (69 MPa). The Young's modulus of the scaffold is increased up to 83.62 MPa. The crystallinity index values of GA-treated scaffolds were increased, and the mechanical characteristics were greatly improved, according to Fourier transform infrared (FTIR) and XRD analysis on the films. The thermogravimetric analysis (TG/DTG/DSC) of the GA treated plasticized nanocellulose scaffold showed maximum decomposition temperature (T_max) at 360.01 °C.

Effect of glycerol plasticizer loading on the physical, mechanical, thermal, and barrier properties of arrowroot (Maranta arundinacea) starch biopolymers

This research was set out to explore the development of arrowroot starch (AS) films using glycerol (G) as plasticizer at the ratio of 15, 30, and 45% (w/w, starch basis) using solution casting technique. The developed films were analyzed in terms of physical, structural, mechanical, thermal, environmental, and barrier properties. The incorporation of glycerol to AS film-making solution reduced the brittleness and fragility of films. An increment in glycerol concentration caused an increment in film thickness, moisture content, and solubility in water, whereas density and water absorption were reduced. The tensile strength and modulus of G-plasticized AS films were reduced significantly from 9.34 to 1.95 MPa and 620.79 to 36.08 MPa, respectively, while elongation at break was enhanced from 2.41 to 57.33%. FTIR analysis revealed that intermolecular hydrogen bonding occurred between glycerol and AS in plasticized films compared to control films. The G-plasticized films showed higher thermal stability than control films. The cross-sectional micrographs revealed that the films containing 45% glycerol concentration had higher homogeneity than 15% and 30%. Water vapour permeability of plasticized films increased by an increase in glycerol concentrations. The findings of this research provide insights into the development of bio-degradable food packaging.

Surface cross-linked thermoplastic starch with different UV wavelengths: mechanical, wettability, hygroscopic and degradation properties

Here, we report a method to improve the properties of thermoplastic starch (TPS) by surface ultraviolet (UV) cross-linking. TPS sheets were prepared by injection molding and coated with an ethanol solution of photo-initiator TPO (2,4,6-trimethyl benzoyl diphenyl phosphine oxide), then, irradiated by UV with different wavelengths for 15 min. Untreated and irradiated TPS sheets were characterized using tensile and bending tests, impact tests, dynamic mechanical thermal analysis (DMTA) and infrared spectroscopy (FTIR). FTIR spectra showed that UV irradiation can effectively trigger surface cross-linking of TPS sheets. The mechanical and dynamic mechanical properties of the TPS were improved and the optimized properties were obtained by 308 nm UV irradiation. A tensile strength of 4.1 MPa, a bending strength of 2.7 MPa, an impact strength of 96.8 kJ m^-2, and the corresponding activation energy of 251.22 kJ mol^-1 were obtained. The water contact angle and moisture absorption of the samples were also investigated and the 308 nm UV irradiated sheets have a contact angle of 74°. Moisture absorption rate as a function of the square root of time showed a sigmoid curve including a linear stage which conforms to Fick's second law. The samples irradiated by 308 nm UV had the lowest equilibrium moisture absorption rate M _∞ and the longest time T ₀ to enter into the Fick's diffusion stage and the lowest slope K and diffusion coefficient D. All samples displayed biodegradable properties when buried in soil. This method has potential applications for agricultural mulch films, packing and medical film products.

Starch/Alkane Diol Materials: Unexpected Ultraporous Surfaces, Near-Isoporous Cores, and Films Moving on Water

The aim of this study was to find alternative starch plasticizers to glycerol that yielded a less tacky material in high-moisture conditions without leading to starch crystallization. A range of glycerol films containing different potential plasticizers (linear alkane diols) were therefore produced, and it was shown that 1,3-propanediol, in combination with glycerol, was a possible solution to the problem. Several additional interesting features of the starch films were however also revealed. The larger diols, instead of showing plasticizing features, yielded a variety of unexpected structures and film properties. Films with 1,6-hexanediol and 1,7-heptanediol showed an ultraporous film surface and near-isoporous core. The most striking feature was that starch films with these two diols moved/rotated over the surface when placed on water, with no other stimulus than the interaction with water. Films with 1,8-octanediol and 1,10-decanediol did not show these features, but there was clear evidence of a structure with phase-separated crystallized diol in a starch matrix, as observed in high-resolution scanning electron microscopy (SEM) images.

Effects of processing conditions and glycerol concentration on rheological and texture properties of starch-based hydrogels produced by high pressure processing (HPP)

Starch-based hydrogels are natural polymeric structures which could be potentially utilized in food, pharma and cosmetic sectors to produce creams, gels and ointments, as well as functional foods and products for personalized nutrition. In this paper, the effects of processing conditions (pressure levels and holding time) on gelation of corn and rice starch solutions were evaluated also in presence of glycerol. Considering the utmost importance of humectants as active moisturizers in gels, their addition in starch solutions has been investigated in view of the industrial exploitation of HPP starch-based hydrogels. Experimental results demonstrated that at 600 MPa the gelation of the formulations tested was homogenous and the hydrogels formed were stable. However, glycerol at 10% concentration played an antagonistic role, being longer processing times necessary to form gels. Viscosity and G' values of rice and corn starch HPP hydrogels decreased with increasing glycerol concentration, particularly for corn starch hydrogels. At all HPP processing conditions investigated, rice starch solutions containing the humectant were more prone to gelation and the hydrogels formed had better texture properties than those based on corn starch. 5% glycerol concentration was identified as the critical value to obtain stable HPP hydrogels with good rheological and texture properties.

Preparation and Properties of Corn Starch/Chitin Composite Films Cross-Linked by Maleic Anhydride

To improve the functional properties of starch-based films, chitin (CH) was prepared from shrimp shell powder and incorporated into corn starch (CS) matrix. Before blending, maleic anhydride (MA) was introduced as a cross-linker. Composite CS/MA-CH films were obtained by casting-evaporation approach. Mechanical property estimation showed that addition of 0–7 wt % MA-CH improved the tensile strength of starch films from 3.89 MPa to 9.32 MPa. Elongation at break of the films decreased with the addition of MA-CH, but the decrease was obviously reduced than previous studies. Morphology analysis revealed that MA-CH homogeneously dispersed in starch matrix and no cracks were found in the CS/MA-CH films. Incorporation of MA-CH decreased the water vapor permeability of starch films. The water uptake of the films was reduced when the dosage of MA-CH was below 5 wt %. Water contact angles of the starch films increased from 22° to 86° with 9 wt % MA-CH incorporation. Besides, the composite films showed better inhibition effect against Escherichia coli and Staphylococcus aureus than pure starch films.

Application of Protein-Based Films and Coatings for Food Packaging: A Review

As the IV generation of packaging, biopolymers, with the advantages of biodegradability, process ability, combination possibilities and no pollution to food, have become the leading food packaging materials. Biopolymers can be directly extracted from biomass, synthesized from bioderived monomers and produced directly by microorganisms which are all abundant and renewable. The raw materials used to produce biopolymers are low-cost, some even coming from agrion dustrial waste. This review summarized the advances in protein-based films and coatings for food packaging. The materials studied to develop protein-based packaging films and coatings can be divided into two classes: plant proteins and animal proteins. Parts of proteins are referred in this review, including plant proteins i.e., gluten, soy proteins and zein, and animal proteins i.e., casein, whey and gelatin. Films and coatings based on these proteins have excellent gas barrier properties and satisfactory mechanical properties. However, the hydrophilicity of proteins makes the protein-based films present poor water barrier characteristics. The application of plasticizers and the corresponding post-treatments can make the properties of the protein-based films and coatings improved. The addition of active compounds into protein-based films can effectively inhibit or delay the growth of microorganisms and the oxidation of lipids. The review also summarized the research about the storage requirements of various foods that can provide corresponding guidance for the preparation of food packaging materials. Numerous application examples of protein-based films and coatings in food packaging also confirm their important role in food packaging materials.

Interactions between polyols and wheat biopolymers in a bread model system fortified with inulin: A Fourier transform infrared study

One of the ways to improve food safety and reduce community health risks is fortification of these products with inulin. Inulin, in spite of the effects and nutritional benefits, will also have undesirable effects on the quality and shelf life of bread. In this study, the interactions between polyols as improvers (i.e. glycerol, sorbitol and propylene glycol) and major biopolymers of wheat flour (i.e. starch and gluten) were examined in model systems fortified with Serish inulin by Fourier transform infrared (FTIR) spectroscopy. The changes in starch structure were estimated focusing on the ratios of the heights of the bands at 1047 and 1022 cm^-1 which expresses the quantity of ordered starch to amorphous starch. At first and 5th days of storage, this ratio of control sample was higher than polyol treated samples. It was proved from Gaussian-Lorenzian curve fitting that the relative contribution of characteristic peaks of β-turns and intramolecular β-sheets was consecutively increased when polyol proportion of models increased. Whereas, content of intermolecular β-sheets and α-helix was slightly decreased with increasing of polyols in the models. Briefly, polyols especially 5% propylene glycol, could be used to reduce the undesirable effects of inulin on the quality parameters of dough and bread.

Thermal Study of Polyols for the Technological Application as Plasticizers in Food Industry

In this work is presented the complete thermal analysis of polyols by direct methods such as simultaneous thermogravimetric and differential thermal analyzer (TGA-DTA), differential scanning calorimetry (DSC), modulated DSC (MDSC), and supercooling MDSC. The different thermal events in the temperature range of 113–553 K were identified for glycerol (GL), ethylene glycol (EG), and propylene glycol (PG). Boiling temperature (T_B) decreased as GL > EG > PG, but increased with the heating rate. GL showed a complex thermal event at 191–199 K, identified as the glass transition temperature (T_g) and devitrification temperature (T_dv), and a liquid–liquid transition (T_L-L) at 215–221 K was identified as the supercooling temperature. EG showed several thermal events such as T_g and T_dv at 154 K, crystallization temperature (T_c) at 175 K, and melting temperature (T_m) at 255 K. PG also showed a complex thermal event (T_g and T_dv) at 167 K, a second devitrification at 193 K, and T_L-L at 245 K. For PG, crystallization was not observed, indicating that, during the cooling, the liquid remained as an amorphous solid.

New technique in starch nanoparticles synthesis

Starch nanoparticles (StNPs) were previously prepared using severe mechanical, physical and/or chemical conditions that takes too long time to produce a little yield of uncontrolled large size of StNP. The current work presents a new technique for the synthesis of StNPs based on the combination between sodium hydroxide and glycerol in aqueous medium during the synthesis process while the precipitation of the StNPs is performed under homogenization at ambient conditions. The new technique is based on three assumptions: 1) the dual impact of sodium hydroxide and glycerol on the swelling and gelatinization of starch as a pre-stage of the synthesis of (StNPs1), 2) the dual impact of glycerol and cooking of starch on the swelling and gelatinization of starch as a pre-stage of the formation of (StNPs2), and 3) the precipitation under homogenization at ambient conditions and its effect on breaking the H- bonds of the starch molecule in both StNPs1 and StNPs2. The importance of this technique arises from the ease of the process, the eco-friendly chemicals and the combination between the mechanical and chemical processes. NS (native starch), StNPs1 and StNPs2 were characterized using FTIR, XRD, TGA and TEM. TEM of StNPs1 showed a well-defined round particles uniformly distributed with size of about 62.5nm. StNPs2 showed a non-specific shape starch particles.

Controlling the Resistive Switching Behavior in Starch-Based Flexible Biomemristors

Implementation of biocompatible materials in resistive switching memory (ReRAM) devices provides opportunities to use them in biomedical applications. We demonstrate a robust, nonvolatile, flexible, and transparent ReRAM based on potato starch. We also introduce a biomolecular memory device that has a starch-chitosan composite layer. The ReRAM behavior can be controlled by mixing starch with chitosan in the resistive switching layer. Whereas starch-based biomemory devices which show abrupt changes in current level; the memory device with mixed biopolymers undergoes gradual changes. Both devices exhibit uniform and robust programmable memory properties for nonvolatile memory applications. The explicated source of the bipolar resistive switching behavior is assigned to formation and rupture of carbon-rich filaments. The gradual set/reset behavior in the memory device based on a starch-chitosan mixture makes it suitable for use in neuromorphic devices.

(Quasi-) 2D aggregation of polystyrene-b-dextran at the air-water interface

Polystyrene-b-dextran (PS-b-Dextran) copolymers can be used to prepare dextran brushes at solid surfaces, applying Langmuir-Blodgett deposition. When recording the interfacial pressure versus area isotherms of a PS-b-Dextran monolayer, time-dependent hysteresis was observed upon compression and expansion. We argue that this is due to (quasi-) 2D aggregation of the copolymer at the air-water surface, with three contributions. First, at large area per molecule, a zero surface pressure is measured; we ascribe this to self-assembly of block copolymers into surface micelles. At intermediate area we identify a second regime ("desorption regime") where aggregation into large patches occurs due to van der Waals attraction between PS blocks. At high surface pressure ("brush regime") we observe hysteretic behavior attributed to H-bonding between dextran chains. When compared to hysteresis of other amphiphilic diblock copolymers (also containing PS, e.g., polystyrene-b-poly(ethylene oxide)) a general criterion can be formulated concerning the extent of hysteresis: when the hydrophobic (PS) block is of equal size as (or bigger than) the hydrophilic block, the hysteresis is maximal. The (quasi-) 2D aggregation of PS-b-Dextran has significant implications for the preparation of dextran brushes at solid surfaces using Langmuir-Blodgett deposition. For each grafting density the monolayer needs to relax, up to several hours, prior to transfer.