Research background. Amaranth flour (Amaranthus hypochondriacus) produces films with excellent barrier properties against water vapor, allowing food preservation, but the mechanical properties are poor versus to synthetic films. One strategy to improve these properties is the incorporation of nanoparticles. The particles can also serve as a vehicle for the addition of antioxidants agents into the films. The objective of this work was to optimize the formulation for preparation of amaranth flour films treated with antioxidant chia (Salvia hispanica L.) extract-loaded chitosan particles using RSM.
Experimental approach. Chitosan nanoparticles with the extract were synthesized by ionic gelation, and the films were made by the casting method. Three independent variables were assigned: amaranth flour (4-6 %), glycerol (25-35 %), and chitosan nanoparticles loaded with the chia extract (0-0.75 %). We then evaluated the physical (thickness), mechanical (tensile strength, Young´s modulus, and elongation), barrier (water vapor permeability, moisture, and water solubility), and antioxidant properties of the films. The experimental results of the properties were analyzed using a Box-Behnken experimental design generating 15 runs with three replicates at the central point.
Results and conclusions. Second and third order polynomial models were obtained from the ANOVA analysis of the evaluated responses, and high coefficients of determination were found (0.91-1.0). The films presented a water vapor permeability of 0.82-2.39·10-7 (g·mm)/(Pa·s·m2), a tensile strength of 0.33-1.63 MPa, and antioxidant activity of 2.24-5.65 %. The variables had different effects on the films: The glycerol negatively affected their properties, and the permeability values increased with amaranth flour concentration. The nanoparticles improved the mechanical, barrier, and antioxidant properties of the films versus films without nanosystems. The optimal formulation was 4 % amaranth flour, 25 % of glycerol, and 0.36 % of chitosan nanoparticles. The optimized films had better mechanical (1.62 MPa) properties, a low water vapor permeability value (0.91·10-7 (g·mm)/(Pa·s·m2)), and moderate antioxidant activity (6.43 %).
Novelty and scientific contribution. The results show the effect of chitosan nanoparticles on the properties of amaranth flour films for the first time. The resulting equations are useful in the design of food packaging.
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