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.

Development of edible films based on differently processed Atlantic halibut (Hippoglossus hippoglossus) skin gelatin

The gelatin prepared from the skins of the Atlantic halibut (Hippoglossus hippoglossus) was investigated for the development of edible films plasticized with 30g sorbitol/100g gelatin. Two types of dry gelatin preparations were obtained depending on whether an intermediate evaporation step at 60 degrees C in the drying procedure is included or not. The amino acid composition, molecular weight distribution (determined by SDS-polyacrylamide gel electrophoresis) and glass transition temperature (determined by differential scanning calorimetry) of the gelatins were determined and related to some physical properties of the resulting films. The gelatin extracted from the halibut skins showed a suitable filmogenic capacity, leading to transparent, weakly colored, water-soluble and highly extensible films. The intermediate evaporation step at 60 degrees C induced thermal protein degradation, causing the resulting films to be significantly less resistant and more extensible. No differences in water vapor permeability, viscoelasticity, glass transition or color properties were evidenced between the two gelatins tested. (C) 2007 Elsevier Ltd. All rights reserved.

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.

Synthesis and characterization of NiMn(2)O(4) nanoparticles using gelatin as organic precursor

Nanoparticles of NiMn(2)O(4) were successfully obtained by mixing gelatin and inorganic salts NiCl(2) center dot 6H(2)O and MnCl(2) center dot 4H(2)O in aqueous solution. The mixture has been synthesized at different temperatures and resulted in NiMn(2)O(4) nanoparticles with crystallites size in the range of 14-44 nm, as inferred from X-ray powder diffraction (XRPD) data. We have also observed that both the average crystallite size and the unit cell parameters increase with increasing synthesis temperature. Magnetic measurements confirmed the presence of a magnetic transition near 110K. (C) 2008 Published by Elsevier B.V.

Magnetic resonance and conductivity study of gelatin-based proton conductor polymer electrolytes

This work report results from proton nuclear magnetic resonance (NMR), continuous-wave (CW-EPR) and pulsed electron paramagnetic resonance (P-EPR) and complex impedance spectroscopy of gelatin-based polymer gel electrolytes containing acetic acid. cross-linked with formaldehyde and plasticized with glycerol. Ionic conductivity of 2 x 10(-5) S/cm was obtained at room temperature for samples prepared with 33 wt% of acetic acid. Proton ((1)H) line shapes and spin-lattice relaxation times were measured as a function of temperature. The NMR results show that the proton mobility is dependent on acetic acid content in the plasticized polymer gel electrolytes. The CW-EPR spectra, which were carried out in samples doped with copper perchlorate, indicate the presence of the paramagnetic Cu(2+) ions in axially distorted sites. The P-EPR technique, known as electron spin echo envelope modulation (ESEEM), was employed to show the involvement of both, hydrogen and nitrogen atoms, in the copper complexation of the gel electrolyte. (C) 2009 Elsevier Ltd. All rights reserved.

NMR and conductivity study of gelatin-based polymer electrolytes

Nuclear Magnetic Resonance spectroscopy (NMR) and complex impedance spectroscopy have been used to study gelatin-based polymer electrolytes plasticized with glycerol and containing lithium perchlorate. The studied samples were prepared with salt concentration of 7.9 wt% and 10.3 wt%. Ionic conductivity of about 10(-5) S/cm was obtained at room temperature for both samples. Lithium (Li-7) and proton (H-1) lineshapes and spin-lattice relaxation times were measured as a function of temperature. The Li-7 NMR relaxation results indicate that the ionic mobility in this system is comparable to those found in other plasticized polymer electrolytes.

All solid-state electrochromic devices with gelatin-based electrolyte

6 x 8cm(2) electrochromic devices (ECDs) with the configuration K-glass/EC-layer/electrotype/ion-storage (IS) layer/K-glass, have been assembled using Nb2O5:Mo EC layers, a (CeO2)(0.81)-TiO2 IS-layer and a new gelatin electrolyte containing Li+ ions. The structure of the electrolyte is X-ray amorphous. Its ionic conductivity passed by a maximum of 1.5 x 10(-5) S/CM for a lithium concentration of 0.3g/15ml. The value increases with temperature and follows an Arrhenius law with an activation energy of 49.5 kJ/mol. All solid-state devices show a reversible gray coloration, a long-term stability of more than 25,000 switching cycles (+/- 2.0 V/90 s), a transmission change at 550 nm between 60% (bleached state) and 40% (colored state) corresponding to a change of the optical density (Delta OD = 0. 15) with a coloration efficiency increasing from 10cm(2)/C (initial cycle) to 23cm(2)/C (25,000th cycle). (c) 2007 Elsevier B.V. All rights reserved.

Gelatin-based protonic electrolyte for electrochromic windows

Proton-conducting gel polymer electrolytes based on gelatin plasticized with glycerol and containing acetic acid were investigated, characterized, and applied to electrochromic window. For glycerol contents varying from 7% to 48%, the conductivity of the uniform and predominantly amorphous gel electrolyte was found to follow a Vogel-Tamman-Fulcher behavior with the temperature. Typically, for the electrolyte chosen to make 7 x 2 cm(2) electrochromic smart window with the configuration: glass/fluor-doped tin oxide (FTO)/WO(3)/gelatin electrolyte/CeO(2)-TiO(2)/FTO/glass and containing 28% of glycerol, the conductivities were found to be of the order of 5 x 10(-5) S/cm at room temperature and 3.6 x 10(-4) S/cm at 80 A degrees C. The device was characterized by spectroelectrochemical techniques and was tested up to 10,000 cycles showing a fast coloring/bleaching behavior, where the coloring process was achieved in 10 s and the bleaching in 2 s. The transmission variation at the wavelength of 550 nm was about 15%. The cyclic voltammograms showed a very good reversibility of the cathodic/anodic processes, and the charge density was about 3.5 mC/cm(2). The memory tests showed that the transmittance in the colored state increased by 8% in 90 min after removing the potential.

Optimization of performances of gelatin/LiBF(4)-based polymer electrolytes by plasticizing effects

Gelatin is a cheap and abundant natural product with very good biodegradation properties and can be used to obtain acetic acid or LiClO(4)-based gel polymer electrolytes (GPEs) with high ionic conductivity and good stability. This article presents results of GPEs obtained by the plasticization of gelatin and addition of LiBF(4), where the optimization of the system was achieved by using a factorial design type 22 with two variables: glycerol and LiBF(4). From this analysis it was stated that the effect of glycerol as a plasticizer on the ionic conductivity results is much more important than the effect obtained by varying the lithium salt content or the effect of the interaction of both variables. Also all the samples were characterized by X-ray diffraction measurements, UV-vis-NIR spectroscopy and scanning electron microscopy (SEM) and impedance spectroscopy. The ionic conductivity results of all analyzed samples as a function of temperature obey predominantly an Arrhenius relationship and the samples are stable up to 160 degrees C. Good conductivity results combined with transparency and good adhesion to the electrodes have shown that gelatin-based GPEs are very promising materials to be used as solid electrolytes in electrochromic devices. (C) 2009 Elsevier Ltd. All rights reserved.

Optimisation of the microencapsulation of tuna oil in gelatin-sodium hexametaphosphate using complex coacervation.

The microencapsulation of tuna oil in gelatin-sodium hexametaphosphate (SHMP) using complex coacervation was optimised for the stabilisation of omega-3 oils, for use as a functional food ingredient. Firstly, oil stability was optimised by comparing the accelerated stability of tuna oil in the presence of various commercial antioxidants, using a Rancimat™. Then zeta-potential (mV), turbidity and coacervate yield (%) were measured and optimised for complex coacervation. The highest yield of complex coacervate was obtained at pH 4.7 and at a gelatin to SHMP ratio of 15:1. Multi-core microcapsules were formed when the mixed microencapsulation system was cooled to 5 °C at a rate of 12 °C/h. Crosslinking with transglutaminase followed by freeze drying resulted in a dried powder with an encapsulation efficiency of 99.82% and a payload of 52.56%. Some 98.56% of the oil was successfully microencapsulated and accelerated stability using a Rancimat™ showed stability more than double that of non-encapsulated oil.

Gelatin microparticles containing propolis obtained by spray-drying technique: preparation and characterization

Gelatin microparticles containing propolis extractive solution (PES) were prepared by spray-drying technique. The optimization of the spray-drying operating conditions and the proportions of gelatin and mannitol were investigated. Regular particle morphology was obtained when mannitol was used, whereas mannitol absence produced a substantial number of coalesced and agglomerated microparticles. Microparticles had a mean diameter of 2.70 mum without mannitol and 2.50 mum with mannitol. The entrapment efficiency for propolis of the microparticles was upto 41 % without mannitol and 39% with mannitol. The microencapsulation by spray-drying technique maintained the activity of propolis against Staphylococcus aureus. These gelatin microparticles containing propolis would be useful for developing intermediary or eventual propolis dosage form without the PES' strong and unpleasant taste, aromatic odour, and presence of ethanol. (C) 2003 Elsevier B.V. All rights reserved.

Effect of the addition of soy lecithin and Yucca schidigera extract on the properties of gelatin and glycerol based biodegradable films

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)