Preparation of nanoemulsions containing unsaturated fatty acid concentrate-chitosan capsules.

HYPOTHESIS: Fish oil is rich in unsaturated fatty acids (ω-3), which are highly susceptible to oxidative degradation. The use of encapsulation process to retard the fatty acid oxidation is an interesting alternative. In this work, nanoemulsions containing capsules of unsaturated fatty acids concentrate (UFAC) using chitosan as wall material were prepared and characterized. EXPERIMENTS: The UFAC were obtained from carp viscera and chitosan was obtained from shrimp wastes. The nanocapsules were prepared by the emulsion method. Four formulations were tested, using different combinations of chitosan concentration and homogenization times. In the more suitable conditions, the emulsion was freeze-dried to obtain a microstructure with capacity to increase the capsules stability. FINDINGS: The results showed that the nanocapsules presented a spherical shape. The use of low wall material concentration and high homogenization time provided nanocapsules with smallest size (332 nm) and lowest polydispersity index (0.214). The microstructure obtained by freeze drying was irregular and porous. The peroxide values demonstrated that the microstructure was able to protect the UFAC regarding to primary oxidation. The encapsulation efficiency was 74.1%, showing that chitosan has potential to be used as encapsulating agent for unsaturated fatty acid concentrate (UFAC).

Chitosan scaffold as an alternative adsorbent for the removal of hazardous food dyes from aqueous solutions.

HYPOTHESIS: The dye adsorption with chitosan is considered an eco-friendly alternative technology in relation to the existing water treatment technologies. However, the application of chitosan for dyes removal is limited, due to its low surface area and porosity. Then we prepared a chitosan scaffold with a megaporous structure as an alternative adsorbent to remove food dyes from solutions. EXPERIMENTS: The chitosan scaffold was characterized by infrared spectroscopy, scanning electron microscopy and structural characteristics. The potential of chitosan scaffold to remove five food dyes from solutions was investigated by equilibrium isotherms and thermodynamic study. The scaffold-dyes interactions were elucidated, and desorption studies were carried out. FINDINGS: The chitosan scaffold presented pore sizes from 50 to 200 µm, porosity of 92.2±1.2% and specific surface area of 1135±2 m(2) g(-1). The two-step Langmuir model was suitable to represent the equilibrium data. The adsorption was spontaneous, favorable, exothermic and enthalpy-controlled process. Electrostatic interactions occurred between chitosan scaffold and dyes. Desorption was possible with NaOH solution (0.10 mol L(-1)). The chitosan megaporous scaffold showed good structural characteristics and high adsorption capacities (788-3316 mg g(-1)).

Optimization and kinetic analysis of food dyes biosorption by Spirulina platensis.

The biosorption of food dyes acid blue 9 and FD&C red no. 40 onto Spirulina platensis was studied. A full factorial design was used to analyze the effects of pH (2-4), stirring rate (50-400 rpm) and contact time (20-100 min) on biosorption capacity. In the best conditions, biosorption kinetics was analyzed and the experimental data were fitted with four kinetic models. The best conditions were: pH 2, 400 rpm and 100 min for acid blue 9, and pH 2, 225 rpm and 100 min for FD&C red no. 40. In these conditions, the biosorption capacities were 1653.0 mg g(-1) for acid blue 9 and 400.3 mg g(-1) for FD&C red no. 40. For both dyes, the Avrami kinetic model was the more appropriate to represent the experimental data. These results showed that the S. platensis is a suitable biosorbent for removal of food dyes from aqueous solutions.