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.

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.