Blends of chitosan (from Cuban lobster) and clay micro/nanoparticles were prepared by dispersion of the clay particles in the film matrix and the films obtained were characterized in terms of water solubility, water vapor, oxygen and carbon dioxide permeability, optical, mechanical and thermal properties using an Instron universal testing machine, differential scanning calorimetry, thermogravimetric analyses and scanning electron microscopy (SEM). The water vapor barrier properties of the films were significantly improved by incorporation of clay in their composition, while the water solubility decreased as the clay concentration increased (for a constant chitosan concentration). The tensile strength of chitosan/clay films increased significantly with increasing chitosan and clay concentrations, while the values of elongation decreased slightly for high values of chitosan concentration. T m increased with the increase of chitosan concentration, but the changes in T m with the addition of clay were not significant. Polynomial models were fitted to the experimental data in order to facilitate future design of chitosan/ clay film systems.

The aim of this work was to evaluate the influence of glycerol and corn oil on physicochemical properties of polysaccharide-based films. The polysaccharides used were galactomannan from Gleditsia triacanthos and chitosan. Fourier-transform infrared spectroscopy, differential scanning calorimetry and thermogravimetric analysis were performed, together with determinations of moisture content, solubility, water vapor permeability and mechanical properties. Structureeproperties relationships were established, relating the two polysaccharides' structures with the way they interact with water, other film's constituents (glycerol and oil) and the resulting properties. The presence of glycerol and corn oil originated a more hydrophilic structure and a decreased affinity of the film matrix to water, respectively, in both polysaccharides. However, the two polysaccharides presented different behaviors in terms of glass transition temperature, water vapor permeability and elongation-at-break that have been related with the particularities of their structure: while for the galactomannan the specific sorption sites for water are the OeH groups, for chitosan those are OeH and/or NH 2 groups. The present work provides insight regarding the physicochemical properties of polysaccharide-based films and established relationships with polymers' structure, showing that the two polysaccharides studied here have adequate properties to be used as packaging materials for specific food applications.

Hydrocolloids from seaweeds have interesting functional properties, such as antioxidant activity and gelling ability. A polysaccharide was isolated by aqueous extraction at 90 C from the red seaweed Gracilaria birdiae (Gb), with a yield of 27.2% of the seaweed dry weight. The sulfate content of the polysaccharide was 8.4% and the main sugars present were galactose (65.4 mol%), 3,6-anhydrogalactose (25.1 mol%) and 6-O-methylgalactose (9.2 mol%). Gel permeation chromatography showed that Gb polysaccharide is a heterogeneous system, with molar mass at the main peak of 3.7 Â 10 5 g mol À1 and a shoulder of 2.6 Â 10 6 g mol À1. The sulfated polysaccharide of Gb characterized by FTIR exhibits the characteristic bands of agarocolloids (at 1375 and 770 cm À1). The rheological behavior of Gb sulfated polysaccharide exhibits a gel-like behavior close to the one observed in commercial agar. The antioxidant properties of Gb sulfated polysaccharide were evaluated by measuring DPPH freeradical scavenging effect, showing that this polysaccharide has a moderate effect in inhibiting the formation of those radicals.

The development of mixed systems, formed by locust bean gum (LBG), and k-carrageenan (k-car) can offer new interesting applications such as the development of edible films with particular properties. kcar/LBG blend films with different ratios were developed, and their effects on films' physical properties were assessed. Thermogravimetric analysis (TGA), X-ray diffraction (XRD) patterns, dynamic mechanical analysis (DMA) and Fourier-transform infrared (FTIR) spectroscopy techniques were used to highlight the interactions between the two polysaccharides. The addition of k-car to LBG improved the barrier properties of the films leading to a decrease of water vapor permeability (WVP). Improved values of elongation-at-break (EB) were registered when the ratio of k-car/LBG was 80/20 or 40/60 (% w/w). Moreover, the k-car/LBG blend films enhance the tensile strength (TS) compared to k-car and LBG films. FTIR results suggested that hydrogen bonds interactions between k-car and LBG have a great influence in films' properties e.g. moisture content, WVP. Therefore, different k-car/LBG ratios can be used to tailor edible films with enhanced barrier and mechanical properties.

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This work presents a methodology for the extraction of galactomannans from seeds of four different species of Leguminosae (Adenanthera pavonina, Caesalpinia pulcherrima, Gleditsia triacanthos and Sophora japonica) to be used e.g. in the food and biomedical industries. The galactomannans were obtained by aqueous extraction followed by a precipitation with ethanol. This methodology is simpler and easier to perform than other existing extraction and purification methodologies, and because it avoids the use of organic solvents (other than ethanol), it is able to generate food grade substances and is environmentally friendlier. The yield of extraction in different stages of the process, monosaccharide composition, as well as physical and chemical parameters of the isolated galactomannans were determined and compared with previously published results. The mannose/galactose ratio of the extracted galactomannans ranged from 1.35 (A. pavonina) to 5.75 (S. japonica). The intrinsic viscosity ranged from 11.34 dL/g (C. pulcherrima) to 8.74 dL/g (S. japonica), while the viscosity average molecular mass ranged between 1.81 Â 10 6 Da and 1.17 Â 10 6 Da (A. pavonina > C. pulcherrima > G. triacanthos > S. japonica). The results confirm the suitability of the extraction and purification procedure to obtain galactomannans from non-traditional sources.

a b s t r a c tGalactomannans of Gleditsia triacanthos, Caesalpinia pulcherrima and Adenanthera pavonina were structurally and thermally characterized. Methylation analyses confirmed that these three galactomannans are composed by a 4-linked mannose polymer with galactose side chains attached at the C6 position. G. triacanthos galactomannan had an estimated average degree of polymerization of 224 mannose residues, with a degree of branching of 0.24, C. pulcherrima galactomannan had a degree of polymerization of 252 and a degree of branching of 0.30, and A. pavonina galactomannan had a degree of polymerization of 475 and a degree of branching of 0.60. Enzymatic hydrolysis with endo-␤-mannanase and the subsequent analyses of the low molecular weight fraction by ESI-MS/MS indicated the presence of characteristic structural features of galactomannans. Furthermore, acetyl and pentosyl residues were detected in the galactomannan of G. triacanthos and analyses of higher molecular weight fractions from G. triacanthos were performed, confirming that presence. Differential scanning calorimetry (DSC) showed the presence of two peaks related with water loss, confirmed by thermogravimetric analysis (TGA). The different compositions of galactomannans with different mannose content and different molecular weights influence their thermal behaviour. A higher content of mannose lead to higher values of the enthalpy change (first thermal transition) and glass transition temperature (T g ), while the enthalpy change of the second thermal transition was influenced by the viscosity average molecular weight (Mv) of the samples.This work provides understanding of structural and thermal properties of three galactomannans from non-conventional sources, thus contributing to a better insight on their possible food, pharmaceutical or biomedical applications.

This study aimed at determining the effect of chitosan coating on shelf life extension of salmon ( Salmo salar ) fillets. The success of edible coatings depends highly on their effective wetting capacity of the surfaces on which they are applied. In this context in a first stage the surface properties of salmon fillets and the wetting capacity of the coatings on fish were evaluated. In terms of wettability there were no significant differences (p > 0.05) between the solutions presenting higher values (solutions 1-4); therefore, solution 1 with a spreading coefficient (Ws) of -4.73 mN m(-1), was chosen to be subsequently analyzed and applied on fish fillets. For shelf life analyses the fillets were coated and stored at 0 °C for 18 days. The control and coated fish samples were analyzed periodically for total aerobic plate count (TPC), pH, total volatile base nitrogen (TVB-N), trimethylamine (TMA), thiobarbituric acid (TBA), and ATP breakdown products (K value). The results showed that fish samples coated with chitosan presented a significant reduction (p < 0.05) for pH and K value after 6 days and for TVB, TMA, and TBA values after 9 days of storage, when compared to control samples. In terms of microbial growth, a slower increase in TPC was observed for the coated fish, indicating that chitosan-based coatings were effective in extending for an additional 3 days the shelf life of the salmon. These results demonstrate that chitosan-based coatings may be an alternative for extending the shelf life of salmon fillets during storage at 0 °C.