Innovative Antimicrobial Chitosan/ZnO/Ag NPs/Citronella Essential Oil Nanocomposite—Potential Coating for Grapes

Abstract

New packaging materials based on biopolymers are gaining increasing attention due to many advantages like biodegradability or existence of renewable sources. Grouping more antimicrobials agents in the same packaging can create a synergic effect, resulting in either a better antimicrobial activity against a wider spectrum of spoilage agents or a lower required quantity of antimicrobials. In the present work, we obtained a biodegradable antimicrobial film that can be used as packaging material for food. Films based on chitosan as biodegradable polymer, with ZnO and Ag nanoparticles as filler/antimicrobial agents were fabricated by a casting method. The nanoparticles were loaded with citronella essential oil (CEO) in order to enhance the antimicrobial activity of the nanocomposite films. The tests made on Gram-positive, Gram-negative, and fungal strains indicated a broad-spectrum antimicrobial activity, with inhibition diameters of over 30 mm for bacterial strains and over 20 mm for fungal strains. The synergic effect was evidenced by comparing the antimicrobial results with chitosan/ZnO/CEO or chitosan/Ag/CEO simple films. According to the literature and our preliminary studies, these formulations are suitable as coating for fruits. The obtained nanocomposite films presented lower water vapor permeability values when compared with the chitosan control film. The samples were characterized by SEM, fluorescence and UV-Vis spectroscopy, FTIR spectroscopy and microscopy, and thermal analysis.

Understanding the Barrier and Mechanical Behavior of Different Nanofillers in Chitosan Films for Food Packaging

“…In another study also using ZnO NPs to improve the barrier properties of the chitosan film, a decrease in WVP with the addition of ZnO NPs was reported [ 64 ]. According to the authors, when ZnO NPs are incorporated, structures with greater firmness are formed due to the interaction of the metal oxide NP and chitosan, generating a more complex path for the water molecules to diffuse through.…”

“…The addition of both nanoparticles to chitosan also showed satisfactory and better values than just the use of one of the compounds. Moreover, they also included citronella essential oil, and this formulation containing the four components presented the lowest value of WVP [ 64 ].…”

Characterization of Carboxymethyl Cellulose Films Incorporated with Chinese Fir Essential Oil and Their Application to Quality Improvement of Shine Muscat Grape

“…The treatment methods of postharvest grapes include physical methods, such as UV irradiation and sonication; biological methods, such as using yeast species to inhibit B. cinerea [18]. Moreover, the coatings were prepared from natural polymers can protect grapes [19,20]. In various studies, SO 2 synthetic fungicide can also preserve grapes, but the residues of chemical preservatives can harm human health [21], so the development of sustainable safe preservatives has become the mainstream of research.…”

Applications of Natural Antimicrobials in Food Packaging and Preservation

“…Total polyphenol content of laper .OLE samples was 216.5 ± 2.9 mg GAE/100 g. Further HPLC-DAD analysis revealed the presence of seven main compounds of which oleuropein is the main component (63.03%), followed by luteolin-7–glucoside (11.28%), apigenin-7-glucoside (8.15%), and hydroxytyrosol (5.93%). Motelica et al [ 3 ] obtained biodegradable antimicrobial films to be used as packaging material. Those films were based on chitosan, as polymer, with ZnO and Ag nanoparticles as filler/antimicrobial agents that were loaded with citronella essential oil in order to increase the antimicrobial activity of the films.…”

“…Somrani et al [ 1 ] applied them to fight biofilms formed in the food processing industries. Djenane et al [ 2 ], Amor et al [ 4 ] and Martelli et al [ 6 ] added the antimicrobials directly to the foods, while Motelica et al [ 3 ], Jaśkiewicz et al [ 5 ] and Lee et al [ 7 ] included them in the packaging material.…”