Influence of PH on the properties of sodium alginate films with norbixin salt

Environmental pollution caused by synthetic packaging materials has increased interest in biodegradable polymers. Sodium alginate is a linear polymer with the ability to form biodegradable films with good mechanical properties. Norbixin is a carotenoid with hydrophilic character and antioxidant properties that can be incorporated in the polymeric matrix. This work's objective was to evaluate the influence of pH (3.0, 7.0, and 11.0) on the properties of biodegradable sodium alginate films with norbixin salts. The pH did not influence water solubility, hydration capacity, colorimetric parameters, thermal properties, and the migration of the pigments into acidic aqueous solutions. The film prepared with pH 11.0 showed a more cohesive structure, with better sodium alginate-norbixin interaction. In addition, it showed lower water activity, higher tensile strength, and higher pigment migration in the lipid medium and good antioxidant activity in sunflower oil stored at accelerated conditions for up to 3 days. Practical applications Although biodegradable films are not intended to completely replace traditional synthetic packaging, they have the potential to reduce their use, in addition to acting as controlled release systems for bioactive compounds. The use of alternative materials, such as polysaccharides with the incorporation of carotenoids, allows biodegradable packaging to be obtained which has functional properties to preserve food quality and prolong its shelf life. The sodium alginate films with norbixin added can be used as packaging for foods with a high lipid content and susceptible to oxidation, in order to improve their stability during storage.