Gelatin-based films activated with red propolis ethanolic extract and essential oils

Abstract

Red propolis ethanolic extract (RPEE) and essential oils are well-known for their antimicrobial and antioxidant activities. The aim of this study was to develop gelatin-based active films loaded with RPEE in combinations with clove essential oil and/or basil essential oil and to study the effects of these components on the antioxidant, antimicrobial and physical properties of films. The active films were produced by a spreading technique, with RPEE and essential oils in different concentrations. These compounds were evaluated for antioxidant and antimicrobial activities, as well as for their minimal inhibitory concentration and minimal bactericidal concentration. The films were characterized through physical, antimicrobial and antioxidant properties. RPEE and essential oils both presented high antioxidant activity. All essential oils showed antimicrobial activity against all evaluated bacteria, while the RPEE presented activity only against the Gram(+) bacteria. All films showed antioxidant activity. Films with clove essential oil presented the highest total contents of phenol and antioxidant activity. The RPEE in films increased their UV/visible light barrier and modified their thermal properties. Changes in infrared spectra suggested possible interactions between phenols of the active compounds and the gelatin peptides. Overall, physical properties of active films were typical of biopolymer-based films.