Purpose: The purpose of this study was to develop biodegradable edible films with antimicrobial activity by incorporating both apple skin polyphenol (ASP) and thyme essential oil (TEO) into films made from Açaí frozen puree, a tropical fruit product from Brazil.
Methods: The antimicrobial effects of açaí edible films incorporated with ASP and TEO were investigated using a central composite design (CCD). The CCD consisted of 11 treatments. Antimicrobial activity of films against Listeria monocytogenesas well as film properties, including mechanical properties, color and thermal resistance, were evaluated. Results were analyzed using response surface methodology.
Results: Antimicrobial effect of both compounds on açaí edible films was observed. Combination of 3.1% ASP and 6.07% TEO resulted in the film with highest inhibition zone against Listeria monocytogenes, with mean value of 685.4 mm2. Film stiffness was influenced by the interaction of both antimicrobials. Film lightness was influenced by ASP and interaction of both compounds. Film redness was affected by both compounds. Incorporation of both antimicrobials resulted in slightly increased values of b* (yellowness). Incorporation of ASP resulted in enhanced thermal stability of films.
Significance: Knowledge of antimicrobial and physical properties of packaging materials is essential for industrial food application. This work showed the antimicrobial synergy of ASP and TEO when incorporated in açaí films, and demonstrated their potential application on food preservation due to their antibacterial activity and good contribution to film properties.