Physical, mechanical, and antimicrobial properties of active edible film based on milk proteins incorporated with Nigella sativa essential oil

Abstract

In the present study, the effects of type and concentration of plasticizer on an edible film based on milk proteins concentrate were investigated. To achieve this goal, three numerical factors of glycerol concentration (5, 7, and 9% W/V), sorbitol concentration (5, 7, and 9% W/V), and Nigella sativa L. essential oil (NSEO) content (0, 1, and 2% W/V) were evaluated using a Box–Behnken design. Then, optimization was performed using the desirability function based on the minimum values of moisture content and water vapor permeability, as well as the maximum whiteness index. Scanning electron microscopy, Fourier-transform infrared spectroscopy, differential scanning calorimetry, and mechanical tests were used to examine the microscopic structure, functional groups, thermal characteristics, such as melting point, and mechanical properties, respectively. The optimal conditions to produce edible films were obtained using 5% glycerol, 5% sorbitol, and 1.27% NSEO. The results of SEM analysis showed typical morphological characteristics of protein-based films containing essential oils for the optimum film. The mechanical analysis showed that the tensile strength and Young’s modulus of the films decrease and the elongation increases with an increasing amount of plasticizer and adding NSEO. The melting temperature of the optimal film was about 130 °C.