Oregano, thyme, and lemongrass essential oils as antimicrobial agents in gelatin for photographic films

Abstract

The aim of this study was to investigate the suitability of selected essential oils as more environmentally friendly, sustainable antimicrobial agents in photographic films for long‐term data storage. For this purpose, essential oils of oregano, thyme, and lemongrass were added in concentrations ranging from 0.4% to 4% to the gelatin comprising a protective layer for photographic microfilms. The emulsions were analyzed via UV‐Vis for their optical transparency, then tested for their antimicrobial efficacy against Bacillus subtilis, Staphylococcus hominis and Staphylococcus epidermidis. Thin coatings generated by spreading and drying the emulsions onto photographic film substrates were then characterized morphologically via SEM before and after standardized artificial aging procedures. It was found that oregano oil at a concentration of 0.4% maintained the optical and physical properties of the emulsion and proved highly effective against all tested bacteria. Thyme and lemongrass oil also exhibited some antimicrobial activity, however, were not able to inhibit the bacterial growth completely. At higher concentrations of the oils, the gelatin coatings cracked after artificial aging, which makes them unsuitable for the application. To conclude, selected essential oils like oregano oil can be used as an effective antimicrobial agent without compromising the quality of the photographic films.Practical applications: The results of our research can be applied directly to the manufacturing of photographic films, specifically ones intended for long‐term data storage. Furthermore, many applications of gelatin or related materials which require antimicrobial activity, such as food packaging, could be enhanced by the addition of essential oils.