Accelerated Life Testing of Biodegradable Starch Films with Nanoclay Using the Elongation Level as a Stressor.

An attempt was made to evaluate the elongation level as a stressor on biodegradable starch films reinforced with nanoclay using a simple linear model. A total of 120 film units were subjected to increasing elongation levels and the exact break time of the failed units was monitored. Nine different attempts were made to fit the data distribution and the lognormal distribution was chosen as the most suitable because it resulted in the lowest values of the regression fit indices -2LL, AICc and BIC. Following the selection of the best fit, it was, generally, observed that an increase in the elongation level resulted in the decreasing exact break time of the films. Among several models, the best fit was provided by the simple linear model. Based on this model, the acceleration factor was estimated, and it was shown that it increased exponentially while increasing the elongation level. Finally, the probability of failure and the hazard rate of the film units as a function of the elongation level were estimated, demonstrating the applicability of this method as a tool for food packaging film failure prediction.

Effects of the Incorporation of Male Honey Bees on Dough Properties and on Wheat Flour Bread's Quality Characteristics.

Two different levels (5 and 10%) of male honey bees (drones) in powder form were incorporated into wheat flour, and their impact on dough properties and on bread-quality characteristics were investigated. The incorporation of the drone powder to the wheat flour caused a decrease in the extensibility and energy of the dough in the extensograph and an increase in the dough's maximum resistance with increasing levels of the added drone powder. The elongational viscosity values of the dough fortified with drone powder were significantly higher than those of the control wheat flour dough. The breads supplemented with 10% drone powder exhibited lower lightness (L*) values compared to the control bread. The addition of drone powder led to an increase in the total dietary fiber content and insoluble dietary fiber content in the fortified bread. Significant differences in the specific volume values were observed between the control bread and the corresponding ones with 10% drone powder. Upon storage, the moisture content of the crumb of the control bread and of the fortified breads were both significantly decreased, while the addition of the drone powder to the wheat flour bread increased the crumb hardness and gumminess but decreased the cohesiveness of the breads.

Sodium Trimetaphosphate Crosslinked Starch Films Reinforced with Montmorillonite.

Synthetic polymers are the main food packaging material, although they are nonbiodegradable and their recycling process is expensive. A biodegradable, eco-friendly material, with high availability and low cost, such as starch, is a promising solution for the production of films for food packaging. To enhance starch film mechanical and barrier properties, nanoclays have been incorporated within the film matrix. Crosslinking is a well-established method to modify starch properties, but it has not been investigated in combination with nanoclay addition. In the present study, films were developed with starch that was crosslinked through the addition of 5, 15, and 40% wt. sodium trimetaphosphate (STMP) based on dry starch weight. To investigate the interaction between crosslinking and nanoclay addition, montmorillonite (MMT) was added at a 10.5% wt. concentration based on dry starch weight. Experimental data revealed a synergistic effect between STMP crosslinking and MMT addition regarding film thickness, elongation at break, color properties, and opacity. Regarding barrier properties, MMT addition negated the effect of STMP crosslinking, while, in the case of moisture content, it did not alter the effect of STMP crosslinking. Finally, in the case of tensile strength, a synergistic effect followed by a negative interaction was observed. In conclusion, the addition of MMT can potentially enhance, alongside crosslinking, some properties of the films, while other properties are not affected any more than just by crosslinking.

Optimizing the Functional Properties of Starch-Based Biodegradable Films.

A definitive screening design was used in order to evaluate the effects of starch, glycerol and montmorillonite (MMT) concentrations, as well as the drying temperature, drying tray type and starch species, on packaging film's functional properties. Optimization showed that in order to obtain films with the minimum possible thickness, the maximum elongation at break, the maximum tensile strength, as well as reduced water vapor permeability and low opacity, a combination of factors should be used as follows: 5.5% wt starch concentration, 30% wt glycerol concentration on a dry starch basis, 10.5% wt MMT concentration on a dry starch basis, 45 °C drying temperature, chickpea as the starch species and plexiglass as the drying tray type. Based on these results, starch films were prepared, and fresh minced meat was stored in them for 3 days. It was shown that the incorporation of MMT at 10.5% wt on a dry starch basis in the packaging films led to a decreased mesophilic and psychrotrophic bacteria growth factor compared to commercial packaging. When assessed for their biodegradability, the starch films disintegrated after 10 days of thermophilic incubation under simulated composting conditions. Finally, to prove their handling capability during industrial production, the starch films were rewound in a paper cylinder using an industrial-scale rewinding machine.

Characterization and properties of non-granular thermoplastic starch-Clay biocomposite films.

Biocomposite films were prepared using as raw materials non-granular normal maize starch plasticized with glycerol and Na-montmorillonite clay particles in various concentrations. The physicochemical properties of films were studied, and their structure and morphology were investigated using XRD analysis, Thermal analysis, Scanning Electron Microscopy combined with Element Microanalysis. The mechanical characteristics were investigated through tensile test. The results indicated that the presence of clay particles in the starch matrix reduced the water absorption rate of films in comparison to starch films containing glycerol but not clay particles. The biocomposite films exhibited enhanced tensile properties at low glycerol and high clay contents. Best results were obtained for films containing 20 wt% glycerol and 10-20 wt% clay content. It is suggested that the non-granular maize starch, is a suitable raw material for the preparation of biocomposite films with improved structural and mechanical characteristics in comparison to films prepared using granular starch.

Dynamic light scattering and electrophoretic mobility studies of starch-fatty acid complexes in solution.

Electrophoretic mobility and dynamic light scattering measurements were carried out to investigate the physical characteristics of amylose inclusion complexes with a series of long chain fatty acids, in alkaline solution (0.1 N or 0.01 N KOH). Amylose molecules exhibited lower values of electrophoretic mobility compared to those of the amylose-fatty acid complexes. The presence of amylopectin affected the electrophoretic mobility of starch-fatty acid complexes. Particle size distribution measurements of amylose-fatty acid complexes in aqueous suspension (pH 4.6) were performed employing the laser light scattering technique. The size of the diameter of the complexes in alkaline solution was found to be much smaller than that of the size of the complexes in aqueous suspension. The results are discussed in the light of solvent contribution to the conformational changes of the complexes occurred in the environments employed.

An investigation into the structure, morphology and thermal properties of amylomaize starch-fatty acid complexes prepared at different temperatures.

Amylomaize (Hylon VII) starch-fatty acid (capric, myristic, palmitic, stearic, oleic) complexes prepared at 30, 50 or 70°C were studied using XRD, DSC, SEM, TGA and FTIR techniques. XRD diffractograms displayed the typical V-form of complexed amylose regardless the temperature of preparing the complexes. The degree of crystallinity of the complexes increased while the size of the crystals formed decreased as the preparation temperature of the complexes increased. DSC thermograms showed that the dissociation temperature of the complexes was increased proportionally to the chain length increase of the fatty acid. TGA indicated that oleic acid was adequately protected in the form of complexes. SEM micrographs showed the presence of crystals of the complexes either in the form of spherulites or in the form of lamellae. Enzymatic hydrolysis of the complexes led to quantitative recovery of the guest molecules. Hylon VII proved to be a suitable prospective complexing agent for the production of complexes of lipids.

Amylose-fatty acid inclusion complexes as examined by interfacial tension measurements.

Amylose forms complexes with fatty acids under certain conditions, these complexes affect the functional properties of foods and could be potentially used as delivery systems of essential fatty acids in the human organism. This work uses dynamic and equilibrium interfacial tension measurements in order to investigate these complexes. First, the interfacial tension at the water/air interface under the conditions of complex formation (KOH 0.1N, pH=12.7) was measured for three fatty acids (capric, myristic and oleic) at different concentrations. Then, amylose-fatty acid complexes were formed at three different fatty acid to amylose ratios covering a range above and below the saturation concentration of the amylose helix. For all examined systems the dynamic interfacial tension of the mixed amylose-fatty acid solution was significantly higher than this of the fatty acid solution, showing that some of the fatty acid was no longer available to adsorb at the interface and suggesting its inclusion in the complex. Besides, the dynamic interfacial tension of the mixed system was lower compared to the pure amylose solution indicating that some of the fatty acid did not participate in the complexes even at fatty acid/amylose ratios well below the saturation concentration of amylose. Using the isotherm of the three fatty acids it was shown that the fatty acid excess depended on fatty acid-to-amylose ratio.

Morphological characteristics, oxidative stability and enzymic hydrolysis of amylose-fatty acid complexes.

Complexes of amylose with fatty acids varying in carbon chain length and degree of unsaturation were prepared at 30, 50 or 70°C by dissolving amylose in 0.1N KOH and mixing with fatty acid potassium soap solution. The complexes were obtained in solid form as precipitates after neutralization. SEM microscopy revealed that the morphology of the complexes was that of ordered lamellae separated from amorphous regions whereas confocal laser scanning microscopy showed images of the topography of the guest molecules in the complex matrix. FTIR spectroscopy revealed that the absorption peak attributed to carbonyl group of free fatty acid was shifted when the fatty acid was in the form of amylose complex. Thermo-gravimetry showed that the unsaturated fatty acids were effectively protected from oxidation when they were complexed with amylose whereas enzymic hydrolysis experiments showed that the guest molecules were quantitatively released from the amylose complexes.