Chitosan films incorporated with Thymus capitatus essential oil: mechanical properties and antimicrobial activity against degradative bacterial species isolated from tuna (Thunnus sp.) and swordfish (Xiphias gladius)

Abstract

Chitosan-based coatings and films have been widely studied, demonstrating to be an efficient and eco-friendly approach to extend the shelf life of food products. The effect of incorporating essential oil (TCEO) at different concentrations (0.5, 1.0, and 1.5% w/w) on physical, mechanical and antimicrobial properties of chitosan films was studied. The antimicrobial activity of the films was evaluated by agar diffusion method, against 23 spoiling microorganisms isolated from tuna and swordfish (ten , one, one , two, two , five spp., one and one) and ATCC 49138. The films exerted antimicrobial activity against all the tested strain, although not proportional to increasing TCEO concentration. In particular, was the most sensitive species and the inhibition was stable after 72 h. In general, TCEO incorporation in chitosan films, significantly ( < 0.05) decreased the water permeability (from 0.577 ± 0.060 gmm/kPahm at 61% R.U. for chitosan to 0.487 ± 0.037 gmm/kPahm for the film with 1.5% TCEO), the elongation at brake (from 27.322 ± 2.35% for chitosan to 14.695 ± 3.99% for the film with 1.5% TCEO) and increased the tensile strength (from 1.697 ± 0.16% for chitosan to 19.480 ± 2.86% for the film with 1.5% TCEO). Moisture content and water contact angle of the films also showed a similar trend with TCEO introduction, because of crosslinking reaction among the polymer chains and TCEO components. Scanning electron microscopy confirmed structure-properties relationships. These results suggest chitosan films incorporated with TCEO as an alternative treatment to inhibit the growth of degradative bacteria with potential application in the fish industry. The importance of testing more than one strain of the same bacteria species to evaluate the effectiveness of chitosan-essential oils coatings was also demonstrated.

Antimicrobial Films Based on Nanocomposites of Chitosan/Poly(vinyl alcohol)/Graphene Oxide for Biomedical Applications

“…In the films with added GO, the results at 24 h of incubation showed that the addition contributes to completely inhibit the growth of the strains treated with 0.75% of GO and with a greater inhibition than 1.0%, an effect similar to what happens when essential oils are incorporated [53]. The strain with the least inhibition was S. aureus , which showed partial restraint at the concentration of 0.25% of GO, indicating that there is higher resistance by Gram-negative bacteria to inhibition due to CS/PVA effect.…”

The Effect of Edible Chitosan Coatings Incorporated with Thymus capitatus Essential Oil on the Shelf-Life of Strawberry (Fragaria x ananassa) during Cold Storage

“…Our group reported the physical-chemical properties and antibacterial activity of chitosan coating incorporated with Thymus capitatus essential oil (TCEO) against the bacteria involved in the spoilage of tuna and swordfish [41]. A commercial TCEO was selected, as it contained reinforced main components and had a high degree of purity, which proved to be an advantage in increasing antimicrobial properties and in decreasing the fungal decay of fruits [41].…”

Chitosan Beads Incorporated with Essential Oil of Thymus capitatus: Stability Studies on Red Tilapia Fillets

“…The main components of the TCEO identified by coupled gas chromatography-mass spectrometry (GC-MS) analysis [16], corresponding to 25 compounds, where 22 are monoterpenes (97.5%), two sesquiterpenes (2.4%), and as a significant component, carvacrol, which is considered to be a potent antibacterial [16].…”

“…Composition analysis of the TCEO was performed by a coupled gas chromatographer Agilent 1200 with an AT 6890 Series plus mass spectrometer (Agilent Technologies, Palo Alto, CA, USA) [16]. TCEO composition was previously reported and Table S1 presents the main components and relative intensities [16].…”