The innovative fabrication and applications of carvacrol nanoemulsions, carboxymethyl chitosan microgels and their composite films.

Abstract

Carvacrol (CA) was firstly made into physically stable nanoemulsions using an innovative spontaneous emulsification method with carvacrol itself as oil phase without introducing other carrier oils. Self-crosslinking carboxymethyl chitosan (CMC) microgels via intermolecular hydrogen bonds were then fabricated using a simple solvent exchange method with ethanol as poor solvent. The CMC microgels obtained were rapidly deposited on the surface of tin foil using an electrospray technique to produce the CMC films. The stability of the films in water was further intensified by using Ca2+ as cross-linking agent. Also, the carvacrol nanoemulsions (CA-NEs) were loaded into the CMC films by utilizing swelling property of CMC microgels in aqueous solution. The results showed that the CA-NEs@CMC composite films possess satisfactory antioxidant activity, good antibacterial activity against S. aureus and E. coli, and excellent ability to extend the shelf life of wheat bread. We believe that the present strategies to prepare CA-NEs, CMC microgels and their composite films also apply to other types of essential oils and polymers, and the CA-NEs@CMC composite film is an excellent candidate for the active packaging.