Edible packaging coating of encapsulated thyme essential oil in liposomal chitosan emulsions to improve the shelf life of Karish cheese

Edible packaging materials of encapsulated essential oils in biopolymers have been investigated to provide an effective and safe approach for food preservation. In this study, chitosan-based emulsions made of liposomes loaded with thyme essential oil (TEO) were investigated to extend the shelf-life of Karish cheese. Liposomal chitosan emulsions were prepared via reverse-phase evaporation method and its macrostructure was demonstrated. Chitosan-based emulsions with TEO/liposomes, prepared by 2% wt/v chitosan solutions, are stable over 2 months. GC/MS analysis of TEO showed that thymol and p-cymene are the major compounds with 30 and 13.7% respectively. Antimicrobial activities were assessed via visible microbial growth method and total bacteria counts of mesophilic, phsychrotrophic bacteria, yeast and mould over 4 weeks. Visible microbial growth test showed an explicit microbial growth, by the second week, for all cheese samples that are not coated or coated with chitosan solutions. Cheese samples coated with chitosan containing TEO 1 and 2 % v/v stayed safe with accepted microbial counts till the end of third week. However, samples coated with liposomal chitosan emulsions encapsulated TEO 1 and 2% v/v remained in acceptable appearance and microbial counts up to 4 weeks. Coatings showed neutral effects on moisture content, pH and titratable acidity.