Physical and Morphological Characteristics of Edible Composite Film of Sodium Caseinate/Pectin/Zedo Gum Containing Poulk (Stachys schtschegleevii) Extract: Optimizing Bioactivity and Physicochemical Properties

Abstract

In this study, sodium caseinate (6–8%), pectin (0–2%), Zedo gum (0–2%), and Poulk extract (5–25%) were used to produce an optimal bioactive edible film. According to the results, changing the amounts of sodium caseinate, pectin, and Zedo gum affected the physicochemical properties of the films significantly. Developed bioactive films were more effective on Gram-positive bacteria (Staphylococcus aureus PTCC 1431) than Gram-negative bacteria (Escherichia coli PTCC 1763). Poulk extract concentration had a significant effect on the antioxidant activity of developed films (p < 0.05). Furthermore, the interactions between the variables had significantly affected the moisture content (MC), solubility, and water vapor permeability (WVP) of the films. Numerical optimization based on the maximum antimicrobial activity, antioxidant activity, and lightness, as well as the minimum MC, WVP, and solubility, were selected the optimum formulation. Based on these results, the optimal formulation was obtained when sodium caseinate, pectin, Zedo gum, and Poulk extract were 6.74%, 0.89%, 0.37%, and 5.85%, respectively. The morphological characterization of the optimal film by FE-SEM analysis showed typical properties of sodium caseinate films. FTIR analysis used to investigate the interactions of components and functional groups of the optimal formulation. The tensile test of the optimally developed film indicated resistance up to 0.4 MPa stress. Thermal properties of the optimal film investigated by DSC analysis, which indicated temperature resistance of developed bio-composite.