Antimicrobial packaging activity enhancement by lemon essential oil pickering emulsion stabilized with nanocellulose microgel particles

The incorporation of lemon essential oil (LEO) into cellulose nanofibrils (CNF) shows great promise in the field of sustainable antimicrobial packaging, but is challenged by poor water dispersibility of LEO and the low retention within the film. In this study, nanocellulose microgel (MG) was designed as particle stabilizers for emulsifying LEO and highly stable high internal phase Pickering emulsions (HIPE) were successfully fabricated. MG particles were constructed through chemical bonding of polyethyleneimine onto 2,2,6,6-tetramethylpiperidinyl-1-oxide (TEMPO)-oxidized nanocellulose, characterized with excellent interfacial wetting properties (reduction of oil-water interfacial tension from 11.36 to 7.84 mN/m) and antimicrobial activity (the MIC for Listeria monocytogenes was 125 μL/mL). The HIPE was obtained by dispersing LEO into MG water dispersion (0.5 wt%). The HIPE with LEO fraction as high as 75 % maintained stability within pH 5 to pH 9 without phase separation after 6 days. Films cast from HIPE and CNF blends have excellent integrity and high LEO content (38.94 %). When HIPE was added at 9.6 wt%, LEO was effectively encapsulated by CNF and MG, embedded in the film with high retention, and exhibited significant antibacterial effects against Listeria monocytogenes, antibacterial rate up to 100 %. This work, based on MG, achieves high internal phase emulsification of LEO and enhanced retention within the film, providing a novel perspective and strategy for efficient encapsulation of essential oils and their economical application in antimicrobial packaging.