Controlled release system inducing change in stability of volatile essential oil emulsion incorporated in a hydrogel using a responsive polymer for practical active food packaging

Controlled-release systems have garnered significant interest across various industries, particularly in applications involving active compounds. The release of these compounds from packaging improves their functionality and efficiency. Active packaging systems utilizing essential oils have been extensively researched due to their antimicrobial properties and high volatility. However, their rapid depletion during the initial stages restricts their effectiveness and practical applications. This study proposes a humidity-responsive controlled-release active packaging system to overcome this challenge. To enhance emulsion stability, two nonionic emulsifiers, Tween 20 (polyoxyethylene (20) sorbitan monolaurate, water soluble) and Span 60 (sorbitan monostearate, oil soluble), were combined with polyvinyl alcohol (PVA). The resulting formulation was used as a film in the experiment. Using this system, an antimicrobial hydrogel film incorporating lemongrass essential oil (LO), a volatile antimicrobial substance, was fabricated and evaluated for its release behavior, antimicrobial activity, and mechanical properties to assess the film quality. LO-PVA hydrogel films were prepared via casting, and their humidity-responsive release was analyzed at various relative humidity (RH) levels (30, 50, 70, and 90 %) over 72 h. LO retention within the films was 61.29 ± 5.56 % at 26 % RH, decreasing to 9.98 ± 1.42 % at 90 % RH, demonstrating that the release rate of LO increased with higher humidity levels. To assess their practical applications, the antimicrobial properties of the fabricated films were evaluated using microbiological assays and real-food packaging tests with ready-to-eat food. Our findings demonstrate the effectiveness of the developed controlled-release system for fabricating and evaluating antimicrobial hydrogel films, as well as its applicability to active antimicrobial food packaging.