Investigation of the effect of Propolis ethanolic extract on the physicochemical, microstructural, antioxidant and antimicrobial properties of starch-gelatin-polyvinyl alcohol blend film

In this study, biodegradable blend based on wheat starch, gelatin and polyvinyl alcohol was prepared and ethanolic extract of propolis (5, 10 and 20 %) (EPE) as antimicrobial and antioxidant agent was incorporated. The films were prepared by solvent casting method and their microstructural, mechanical, barrier, color, antioxidant and antimicrobial properties were investigated. In the control sample, homogenous structure was not formed due to the incompatibility of the biopolymers with each other, while the addition of EPE caused to formation of uniform structure and cracks were decreased according to SEM observations. FT-IR test approved the formation of new interactions between biopolymers and components of EPE. Addition of EPE caused to decrease the tensile strength, water vapor permeability and opacity. But the elongation to break and yellowness index increased. Total phenol content and antioxidant capacity of the films increased with increasing concentrations of EPE. Different concentrations of EPE significantly affected all properties of the film, exception water absorption. The films containing EPE had more antimicrobial effects on S.aureus compared to E.coli bacteria. Generally, the film containing EPE 10% demonstrated the best physicochemical and functional characteristics. Results of this research revealed that the blend film activated with propolis extract is a good candidate for antioxidant and antimicrobial packaging and increasing the shelf life of foods.