Molecular mobility, composition and structure analysis in glycerol plasticised chitosan films

This study was developed with the purpose to investigate the effect of polysaccharide/plasticiser concentration on the microstructure and molecular dynamics of polymeric film systems, using transmission electron microscope imaging (TEM) and nuclear magnetic resonance (NMR) techniques. Experiments were carried out in chitosan/glycerol films prepared with solutions of different composition. The films obtained after drying and equilibration were characterised in terms of composition, thickness and water activity. Results show that glycerol quantities used in film forming solutions were responsible for films composition; while polymer/total plasticiser ratio in the solution determined the thickness (and thus structure) of the films. These results were confirmed by TEM. NMR allowed understanding the films molecular rearrangement. Two different behaviours for the two components analysed, water and glycerol were observed: the first is predominantly moving free in the matrix, while glycerol is mainly bounded to the chitosan chain. (C) 2013 Elsevier Ltd. All rights reserved.

Natural antimicrobial ingredients incorporated in biodegradable films based on cassava starch

Biodegradable films based on cassava starch and with addition of natural antimicrobial ingredients were prepared using the casting technique. The tensile properties tensile strength (TS) [MPa] and percent elongation (E) at break [%] and the water vapor transmission (WVT) of the biodegradable films were evaluated and compared with the control (without antimicrobial ingredients). The evaluation of the Colony Forming Units per gram [CFU/g] of pan bread slices packed with the best biodegradable films, in terms of packaging performance, was also determined. The addition onto the matrix of only clove and cinnamon powders could reduce the films WVT when compared to the control, however TS and E were lower than the control and the effect of cinnamon was milder regarding this property. Since water activity of the pan bread slices packed with the biodegradable films increased considerably during the storage period, the antimicrobial effect could not be clearly determined. (C) 2010 Published by Elsevier Ltd.

Gelatin-based films containing hydrophobic plasticizers and saponin from Yucca schidigera as the surfactant

The aim of this study was to evaluate the incorporation of hydrophobic plasticizers (acetyltributyl citrate - ATB, tributyl citrate - TB and acetyltriethyl citrate - ATC) in a matrix of gelatin, using the saponin extracted from Yucca schidigera (yucca) as emulsifier, in the production of biodegradable emulsified films using the casting technique. High levels of hydrophobic plasticizers were incorporated, reaching up to 75% of plasticizer in relation to the protein (w/w) for ATB and TB, and up to 60% for ATC. The minimum values of water vapor permeability were 0.08, 0.07 and 0.06 g mm m(-2) h(-1) kPa(-1) for ATB, TB and ATC respectively, with no significant differences (p > 0.05). The water solubility of the films ranged from 21% to 59.5%. Although the WVP decreased, both scanning electron microscopy and laser scanning confocal microscopy indicated that the incorporation of the hydrophobic plasticizers did not occur homogeneously in the film matrix. (C) 2010 Elsevier Ltd. All rights reserved.

Optimization of amaranth flour films plasticized with glycerol and sorbitol by multi-response analysis

The optimal formulation for the preparation of amaranth flour films plasticized with glycerol and sorbitol was obtained by a multi-response analysis. The optimization aimed to achieve films with higher resistance to break, moderate elongation and lower solubility in water. The influence of plasticizer concentration (Cg, glycerol or Cs, sorbitol) and process temperature (Tp) on the mechanical properties and solubility of the amaranth flour films was initially studied by response surface methodology (RSM). The optimized conditions obtained were Cg 20.02 g glycerol/100 g flour and Tp 75 degrees C, and Cs 29.6 g sorbitol/100 g flour and Tp 75 degrees C. Characterization of the films prepared with these formulations revealed that the optimization methodology employed in this work was satisfactory. Sorbitol was the most suitable plasticizer. It furnished amaranth flour films that were more resistant to break and less permeable to oxygen, due to its greater miscibility with the biopolymers present in the flour and its lower affinity for water. (C) 2011 Elsevier Ltd. All rights reserved.

EFFECT OF GLYCEROL ON PHYSICAL PROPERTIES OF CASSAVA STARCH FILMS

In this work, the effect of glycerol on the physical properties of edible films were identified by X-ray diffraction (XRD), differential scanning calorimetry (DSC), infrared (FTIR) and microwave spectroscopy. According to XRD diffractograms, films with 0 and 15% glycerol displayed an amorphous character, and a tendency to semicrystallization, for films with 30% and 45% glycerol. From DSC thermograms, the glass transition (Tg) of the films decreased with glycerol content. However, two Tgs were observed for samples with 30% and 45% glycerol, due to a phase separation. The intensity and positions of the peaks in FTIR fingerprint region presented slight variations due to new interactions arising between glycerol and biopolymer. Microwave measurements were sensitive to moisture content in the films, due to hydrophilic nature of the glycerol. The effect of plasticizer plays, then, an important rule on the physical and functional properties of these films, for applications in food technology.

Development of films based on blends of gelatin and poly(vinyl alcohol) cross linked with glutaraldehyde

Both gelatin and poly(vinyl alcohol) (PVA) can be cross linked with glutaraldehyde (GLU). In the case of gelatin, the GLU reacts with each e-NH2 functional group of adjacent lysine residues, while for PVA, the GLU reacts with two adjacent hydroxyl groups, forming acetal bridges. Thus it can be considered possible to cross link adjacent macromolecules of gelatin and PVA using GLU. In this context, the aims of this work were the development of biodegradable films based on blends of gelatin and poly(vinyl alcohol) cross linked with GLU, and the characterization of some of their main physical and functional properties. All the films were produced from film-forming solutions (FFS) containing 2 g macromolecules (PVA + gelatin)/100 g FFS, 25 g glycerol/100 g macromolecules, and 4 g GLU (25% solution)/100 g FFS. The FFS were prepared with two concentrations of PVA (20 or 50 g PVA/100 g macromolecules) and two reaction temperatures: 90 or 55 degrees C, applied for 30 min. The films were obtained after drying (30 degrees C/24 h) and conditioning at 25 degrees C and 58% of relative humidity for 7 days, and were then characterized. The results for the color parameters, mechanical properties, phase transitions and infrared spectra showed that some chemical modifications occurred, principally for the gelatin. However, in general, all the characteristics of the films were either typical of films based on blends of these macromolecules without cross linking, or slightly higher. A greater improvement in the properties of this material was probably not observed due to the crystallinity of the PVA, which has a melting point above 90 degrees C. The presence of microcrystals in the polymer chain probably reduced macromolecular mobility, hindering the reaction. Thus more research is necessary to produce biodegradable films with improved properties. (C) 2011 Elsevier Ltd. All rights reserved.

Effect of hydrophobic plasticizers on functional properties of gelatin-based films

The aim of this study was the production and characterization of gelatin-based films using hydrophobic plasticizers derived from citric acid and soy lecithin as emulsifier. The films were characterized as to their mechanic properties, permeability to water vapor, opacity, morphology and possible interactions using Fourier transform infrared spectroscopy. Tensile strength values (TS) varied from 36 to 103 MPa, how-ever, the increase in the concentration of plasticizers (acetyltributyl citrate and tributyl citrate) reduced TS by 57% and no relation was observed between plasticizer quantities and the elongation in the quantities tested. Permeability to water vapor varied between 0.17 and 0.34 (g mm/m(2) h kPa), slightly increasing with the increase in concentration of plasticizers. The effectiveness in the use of soy lecithin emulsifier in the homogenization between the compounds could be proven by microscopic observation using confocal laser microscopy. (C) 2009 Elsevier Ltd. All rights reserved.

Study of some physical properties of biodegradable films based on blends of gelatin and poly(vinyl alcohol) using a response-surface methodology

The aim of this work was to study the effect of the hydrolysis degree (HD) and the concentration (C(PVA)) Of two types of poly(vinyl alcohol) (PVA) and of the type (glycerol and sorbitol) and the concentration (C(P)) of plasticizers on some physical properties of biodegradable films based on blends of gelatin and PVA Using a response-surface methodology. The films were prepared with a film forming solutions (FFS) with 2 g of macromolecules (gelatin+PVA)/100 g de FFS. The responses analyzed were the mechanical properties, the solubility, the moisture Content. the color difference and the opacity. The linear model was statistically significant and predictive for puncture force and deformation. elongation at break, solubility in water, Moisture content and opacity. The CPVA affected strongly the elongation at break of the films. The interaction of the HD and the C(P) affected this property. Moreover. the puncture force was affected slightly by the C(PVA). Concerning the Solubility in water, the reduction of the HD increased it and this effect was greater for high CPVA Values. In general. the most important effect observed in the physical properties of the films was that of the plasticizer type and concentration. The PVA hydrolysis degree and concentration have an important effect only for the elongation at break, puncture deformation and solubility in water. (C) 2008 Elsevier B.V. All rights reserved.

Thermomechanical properties of biodegradable films based on blends of gelatin and poly(vinyl alcohol)

The aim of this work was to study the effect of the poly(vinyl alcohol) (PVA) concentration on the thermal and viscoelastic properties of films based on blends of gelatin and PVA using differential scanning calorimetry (DSC) and dynamic-mechanical analysis (DMA). One glass transition was observed between 43 and 49 degrees C on the DSC curves obtained in the first scanning of the blended films, followed by fusion of the crystalline portion between 116 and 134 degrees C. However, the DMA results showed that only the films with 10% PVA had a single peak in the tan 5 spectrum. However, when the PVA concentration was increased the dynamic mechanical spectra showed two peaks on the tan 6 curves, indicating two T(g)s. Despite this phase separation behavior the Gordon and Taylor model was successfully applied to correlate T, as a function of film composition, thus determining k = 7.47. In the DMA frequency tests, the DMA spectra showed that the storage modulus values decreased with increasing temperature. The master curves for the PVA-gelatin films were obtained applying the TTS principle (T(r) = 100 degrees C). The WLF model was thus applied allowing for the determination of the constants C(1) and C(2). The values of these constants increased with increasing PVA concentrations in the blend: C(1) = 49-66 and C(2) = 463-480. These values were used to calculate the fractional free volume of the films at the T(g) and the thermal expansion coefficient of the films above the T(g). (c) 2007 Elsevier Ltd. All rights reserved.

Biodegradable Films Based on Blends of Gelatin and Poly (Vinyl Alcohol): Effect of PVA Type or Concentration on Some Physical Properties of Films

The aim of this work was to develop biodegradable films based on blends of gelatin and poly (vinyl alcohol) (PVA), without a plasticizer. Firstly, the effect of five types of PVA with different degree of hydrolysis (DH) on the physical properties of films elaborated with blends containing 23.1% PVA was studied. One PVA type was then chosen for the study of the effect of the PVA concentration on the mechanical properties, color, opacity, gloss, and water solubility of the films. The five types of PVA studied allowed for films with different characteristics, but with no direct relationship with the DH of the PVA. Therefore, the PVA Celvol (R) 418 with a DH = 91.8% was chosen for the second part, because they produced films with greater tensile strength. The PVA concentration affected all studied properties of films. These results could be explained by the results of the DSC and FTIR analyses, which showed that some interactions between the gelatin and the PVA occurred depending on the PVA concentration, affecting the crystallinity of the films.

The effect of the degree of hydrolysis of the PVA and the plasticizer concentration on the color, opacity, and thermal and mechanical properties of films based on PVA and gelatin blends

The objective of this work was to study the color, opacity, crystallinity, and the thermal and mechanical properties of films based on blends of gelatin and five different types of PVA [poly(vinyl alcohol)], with and without a plasticizer. The effect of the degree of hydrolysis of the PVA and the glycerol concentration on these properties was studied using colorimetry, differential scanning calorimetry (DSC), X-ray diffraction (XRD) and tensile mechanical tests. All films were essentially colorless (Delta E* < 5) and with low opacity ( Y <= 2.1). The DSC results were typical of partially crystalline materials, showing some phase separation characterized by a glass transition (T(g) = 40-55 degrees C), related to the amorphous part of the material, followed by two endothermic peaks related to the melting (T(m) = 100-160 and 170-210 degrees C) of the crystallites. The XRD results confirmed the crystallinity of the films. The film produced with PVA Celvol((R)) 418 (DH = 91.8%) showed the highest tensile resistance (tensile strength = 38 MPa), for films without plasticizer. However, with glycerol, the above-mentioned PVA and the PVA Celvol((R)) 504 produced the least resistant films of all the PVA types. But, although the mechanical properties of the blended films depended on the type of PVA used, there was no direct relationship between these properties and the degree of hydrolysis of the PVA. The properties studied were more closely dependent on the glycerol concentration. Finally, the mechanical resistance of the films presented a linear relationship with the glass transition temperature of the films. (c) 2007 Elsevier Ltd. All rights reserved.

Effect of chemical treatment on the mechanical properties, water vapour permeability and sorption isotherms of gelatin-based films

Proteins contain hydrophilic groups, which can bind to water molecules through hydrogen bridges, resulting in water vapour adsorption. An increase in the degree of cross-linking can be a method to improve the cohesiveness force and functional properties of protein-based films. Thus, the objective of this work was to evaluate the effect of chemical treatment of gelatin with formaldehyde and glyoxal on the mechanical properties, water vapour permeability (WVP) and water vapour sorption characteristics of gelatin-based films. Films were produced using gelatin, with and without chemical treatment. The formaldehyde treatments caused a significant increase in the tensile strength and a reduction in the WVP of films. The Guggenheim-Anderson-De Boer and Halsey models could be used to model the sorption isotherms of films. It was observed that an increase in temperature produced a decrease in water sorption, and the chemical modifications did not affect the monolayer moisture content. Copyright (c) 2007 John Wiley & Sons, Ltd.

Effect of surfactants on the functional properties of gelatin-polysaccharide-based films

The aim of this study was to evaluate the effects of the addition of surfactants sodium stearoyl lactate (SSL) and sucrose ester (SE) on the functional properties of films produced with polysaccharides mixtures (methylcellulose/glucomannan/pectin in 1/4/1 ratio, respectively) and gelatin. The films were produced by the casting method and characterized for their water vapor permeability (WVP), mechanical (tensile strength and elongation to break point), morphological and optical properties. Films with low WVP were obtained with surfactants. Addition of SE to the films with polysaccharide/gelatin ratio of 90/10 showed improved mechanical properties. Films presented smooth surfaces with micro voids and lumpiness, depending on the surfactant tested. Surfactants increased the opacity of the films by a factor of 1-3%. All film properties were dependent on the surfactant affinity for the biopolymer matrix. SE presented more affinity for biopolymer matrix containing high polysaccharide proportion, and SSL presented more affinity for polymer matrix containing high gelatin proportion. The addition of surfactants decreased the water vapor permeability of the films, increasing their hydrophobic character.

Prediction of cassava starch edible film properties by chemometric analysis of infrared spectra

Cassava starch has been shown to make transparent and colorless flexible films without any previous chemical treatment. The functional properties of edible films are influenced by starch properties, including chain conformation, molecular bonding, crystallinity, and water content. Fourier-transform infrared (FTIR) spectroscopy in combination with attenuated total reflectance (ATR) has been applied for the elucidation of the structure and conformation of carbohydrates. This technique associated with chemometric data processing could indicate the relationship between the structural parameters and the functional properties of cassava starch-based edible films. Successful prediction of the functional properties values of the starch-based films was achieved by partial least squares regression data. The results showed that presence of the hydroxyl group on carbon 6 of the cyclic part of glucose is directly correlated with the functional properties of cassava starch films.

Development of Novel Guava Puree Films Containing Chitosan Nanoparticles

One of the overall goals of industries is to use packages that do not cause environmental problems at disposal time, but that have the same properties as the conventional ones. The goal of this study is to synthesize edible films based on hydroxypropyl methylcellulose (HPMC) with guava puree and chitosan (CS) nanoparticles. This was divided into two stages, the first is the synthesis of chitosan nanoparticles and the second is the production of the films. For the nanoparticles, average size and zeta potential measurements were performed. The characterizations of mechanical and thermal properties, solubility and water vapor permeability tests were conducted in the films. It was observed that when the nanoparticles were added to HPMC and guava puree films, they improved their mechanical and thermal properties, as well as decreased the films solubility and permeability. The potential application of the films prepared would be in edible films with flavor and odor to extend the shelf life of products.