Physical and mechanical characterization of microwave and ultrasound-modified zein-corn starch edible films

Abstract

Edible films and coatings are the biodegradable layers of edible components that are used to coat the food surface or wrap the food in the form of film. In this paper, microwave, and ultrasound technologies, at different processing conditions, separately (US, 70M, 30M) or consecutively in different order (US-70M, 70M-US, US-30M, 30M-US) were applied to the film-forming solutions based on zein and corn starch to increase the compatibility between the biopolymers and to improve some of the edible film characteristics. The physical and mechanical properties and the FTIR spectra of the films were determined. The microwave followed by ultrasound treated edible films (70M-US, 30M-US) were found to be smoother and more homogeneous than the other films. Although all films were found to have hydrophilic character, application of microwave and ultrasound technologies together increased the water contact angle values of the films, providing more hydrophobic film surfaces. 70M-US and 30M-US edible films were found to have the highest tensile strength and elongation % values, respectively. The obvious deeper peaks were observed in the amide-III band of FTIR spectra for microwave followed by ultrasound treated films as an indicator of the enhanced compatibility between zein and corn starch in the film matrix.