Influence of photocrosslinking on the retrogradation of wheat starch based films

UV-Cured Biodegradable Methacrylated Starch-Based Coatings

Promising UV-curable starch-based coatings were fabricated by utilizing methacrylated starch. The aqueous methacrylated starch solution was cast on a glass substrate, and UV-cured after drying. The efficiency of UV-curing process was monitored with gel percentage measurements. The thermal and mechanical properties of the fabricated UV-cured coatings were investigated through differential scanning calorimetry and tensile test and compared with the starch-based uncured casted coatings. A complete characterization of the surface properties was performed by means of pencil hardness, adhesion, solvent resistance, and surface tension measurements. The cross-linking by UV-curing significantly enhanced the mechanical and surface properties of the coating. The effect of UV-curing on the biodegradability of the coating was evaluated by following the enzymatic degradation by α-amylase by determining the amount of glucose and maltose released from the coatings. UV-cured methacrylated starch based coating with promising material and surface properties and retained biodegradation potential was demonstrated.

Exploring the Potentialities of Photoinduced Glycation to Steer Protein Functionalities: The Study Case of Freeze-Dried Egg White Proteins/Carbohydrates Mixtures

The capacity of UV-C light to induce glycation and modify functional properties of systems containing freeze-dried egg white proteins and carbohydrates with increasing molecular weight (i.e., glucose, maltose, trehalose and maltodextrin) was studied. Color changes induced by light exposure were taken as typical indicators of glycation. Samples were then analyzed for selected physical (critical concentration, particle size and viscosity), chemical (ovalbumin content) and technofunctional properties (gelling temperature and foaming capacity). The presence of sugars during exposure to UV-C light promoted intense browning and decreased ovalbumin content by circa 30%. Concomitantly, up to a 3-fold increase in critical concentration of the aqueous suspensions of the irradiated protein-carbohydrate powders and changes in particle size were detected. These modifications were consistent with the development of non-enzymatic browning reactions upon UV-C light irradiation. Photoinduced glycation was associated to a decrease in viscosity, a tendency to form gel at temperature lower by up to 8 °C and a better capacity of foam stabilization. The intensity of these changes seems to be affected by the nature of the carbohydrates reacting with proteins, with longer carbohydrates able to produce systems with higher foam stability capacity.

Characterization and performance analysis of composite bioplastics synthesized using titanium dioxide nanoparticles with corn starch

Plastic is an amazing material, and wonderful invention, it has changed the world. Plastic is used everywhere and every day across the globe. But despite its varied uses, its disposal has threatened the environment. Biodegradable plastics can meet these needs and can easily be disposed to the environment. This work focuses on the characterization and performance analysis of starch bioplastics and composite bioplastic to reduce the plastic pollution by its various uses. TGA, DSC, SEM, FTIR, and surface roughness analyses were used to characterize, the mechanical properties, thermal properties and the morphology of the starch bioplastics and composite bioplastic. Starch bioplastics were fabricated using starch vinegar and glycerol. Composite bioplastics ware fabricated using starch, vinegar, glycerol and titanium dioxide. The addition of titanium dioxide improved the tensile strength of the bioplastics from 3.55 to 3.95 MPa and decreased elongation from 88% to 62%. According to Differential Scanning Calorimetry (DSC) Test, the melting point (T_m) and Glass Transition Temperature (T_g) significantly affected by the presence of titanium dioxide (TiO₂). The degree of nano-composite crystallinity was formed by the strong interfacial interaction between the titanium dioxide nanoparticles and the amorphous region of the chain. The decomposition temperature of starch bioplastic was increased by mixing with titanium dioxide nanoparticles. The results gained from SEM showed that better compatible morphologies in composite bioplastic compared to starch bioplastic for its fewer voids, holes, and crack. The functional group O-H, C-H, C=O, and C-O indicate the formation of starch bioplastics and composite bioplastics has already occurred which was confirmed by FTIR spectroscopy. The result is also verified with the available results of other researchers. Therefore, composite bioplastic is a modified elevation of a starch bioplastic with a modified upgrade feature. It can be an alternative to existing conventional plastic, especially packaging applications.

Effects of magnesium hydroxide on the properties of starch/plant fiber composites with foam structure

In this study, magnesium hydroxide (MH) flame-retarded starch/plant fiber composites containing various MH contents (0%, 5%, 15%, 15%) were prepared and named as TF-MH0, TF-MH5, TF-MH10, TF-MH15. Thermal degradation, flame retardancy, mechanical and microscopic characteristics were discussed. The reduction in the maximum thermal degradation rate revealed that the addition of MH provided improvement in the thermal stability of the composite. The horizontal burning test and the limiting oxygen index analysis suggested enhancement in flame retardancy with increasing MH content. Moreover, the density of composites initially decreased and then increased as the MH content increased. The tensile strength was positively correlated with the density, whereas the cushioning performance was negatively correlated with the density. Microscopic analysis showed that there was an interfacial interaction between MH and thermoplastic starch, which not only improves the thermal stability, but also promotes bubble nucleation as a nucleating agent. The cells of TF-MH10 were uniform and dense, thus TF-MH10 had the best buffering performance. Furthermore, the cell structure of TF-MH15 was short in diameter, small in number, and large in skeleton thickness; therefore, TF-MH15 had the highest tensile strength.

Thermoplastic starch processing and characteristics-a review

Canola Council of Canada, Winnipeg, Manitoba, Canada The rising costs of nonrenewable feedstocks and environmental concerns with their industrial usage have encouraged the study and development of renewable products, including thermoplastic starch (TPS). Starch is an abundant, plant-based biodegradable material with interesting physicochemical characteristics that can be exploited, and this has received attention for development of TPS products. Starch exhibits usable thermoplastic properties when plasticizers, elevated temperatures, and shear are present. The choice of plasticizer has an effect on TPS, even when these have similar plasticization principles. Most TPS have glass transition temperature, Tg, in the range of approximately -75 to 10°C. Glassy transition of TPS is detected by differential scanning calorimeter (DSC) and thermodynamic analyzer (DMA), although DMA has been found to be more sensitive and effective. TPS has low tensile properties, typically below 6 MPa in tensile strength (TS). The addition of synthetic polymers, nanoclay, and fiber can improve TS and water-resistance ability. The moisture sorption behavior of TPS is described in GAB and BET models, from which monolayer moisture content and specific area are derived. Current studies on surface tension, gas permeability, crystallinity, and so on of the TPS are also reviewed.

Coordination polymer: synthesis, spectral characterization and thermal behaviour of starch-urea based biodegradable polymer and its polymer metal complexes

A starch-urea-based biodegradable coordination polymer modified by transition metal Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) was prepared by polycondensation of starch and urea. All the synthesized polymeric compounds were characterized by Fourier transform-infrared spectroscopy (FT-IR), ¹H-NMR spectroscopy, ¹³C-NMR spectroscopy, UV-visible spectra, magnetic moment measurements, differential scanning calorimeter (DSC), and thermogravimetric analysis (TGA). The results of electronic spectra and magnetic moment measurements indicate that Mn(II), Co(II), and Ni(II) complexes show octahedral geometry, while Cu(II) and Zn(II) complexes show square planar and tetrahedral geometry, respectively. The thermogravimetric analysis revealed that all the polymeric metal complexes are more thermally stable than the parental ligand. In addition, biodegradable studies of all the polymeric compounds were also carried out through ASTM standards of biodegradable polymers by CO₂ evolution method.

Crystallization of high-amylose starch by the addition of plasticizers at low and intermediate concentrations

The antiplasticization effect of plasticizers (that is, polyols and monosaccharides) in starch films was investigated. Pea starch films were plasticized by various polyols and monosaccharides at the levels of 0% to 25% (w/w, plasticizer/starch). After 14 d of storage at 50% relative humidity, the crystallinity of pea starch films increased with increasing concentration of plasticizers from 0% to 20%. Accordingly, moisture content, water vapor permeability, oxygen permeability, and elongation decreased with increasing plasticizer concentration from 0% to 20%, showing the antiplasticization effect. The addition of plasticizers above 20% reduced the crystallinity of starch films, consequently showing the plasticization effect. The results showed that the addition of the plasticizers facilitated the crystallization of the polymer chains through the antiplasticization phenomenon at the concentration range below 15%. Above 20%, plasticizers performed the conventional plasticization effect. Each plasticizer had different critical concentration where the antiplasticization was converted to plasticization.

Biocomposites of cellulose reinforced starch: improvement of properties by photo-induced crosslinking

In the present study, the composite films have been prepared from the aqueous dispersions of starch with microcrystalline cellulose using glycerol as plasticizer and irradiated under ultraviolet (UV) light using sodium benzoate as photo-sensitizer. Photo-crosslinking was characterized by measuring the water absorption under 100% relative humidity, swelling degree and gel fraction in dimethylsulphoxide (DMSO), upon irradiation time. Both, the incorporation of cellulose and photo-irradiation were found to decrease the water absorption, swelling in DMSO and increase the gel fraction. Thermal transitions indicated the anti-plasticization of amylopectin chains at the fiber/matrix interface. With increasing content of cellulose and photo-irradiation time, the tensile modulus and strength were found to improve. It is summarized that the combination of cellulose reinforcement and photo-crosslinking of matrix has improved the physical and mechanical properties.

Sorption isotherm and plasticization effect of moisture and plasticizers in pea starch film

Pea starch films were produced with various plasticizers (glucose, fructose, mannose, sorbitol, and glycerol). Effects of plasticizer content (4.34 to 10.87 mmol/g of dry starch) and storage relative humidity (RH) (11.3% to 75.4%) on moisture content (MC), tensile strength (TS), elongation (E), modulus of elasticity (EM), and water vapor permeability (WVP) were evaluated using response surface methodology. MC was influenced strongly by RH. Glycerol-plasticized films had the highest MC, indicating that water molecules played a more important role in plasticizing starch films. Monosaccharide-plasticized films and polyol-plasticized films had similar TS values. However, monosaccharide-plasticized films had higher E values and lower EM values than polyol-plasticized films, meaning monosaccharides had better efficiency in plasticizing starch films. Recrystallization happened in glucose- and sorbitol-plasticized films when they were stored in high RH. Sorption isotherm studies showed the similar adsorption and desorption profiles for all 3 monosaccharide-plasticized films and a hysteresis. The Flory-Huggius model fitted experimental data best for starch films, while the BET model fitted the data marginally.