Preparation of bioactive film based on chitosan and essential oils mixture for enhanced preservation of food products.

Recently, the concept of biodegradable and bioactive packaging and surface coating has become a trend. In this work, the bioactive films of chitosan were elaborated following the casting method. Contrary to the films containing the Cinnamomum zeylanicum Blume, Thymus satureioides Cosson, and Syzygium aromaticum essential oils (EOs) mixtures, the control film was thin, colorless, and showed high moisture content, swelling degree, and elongation at break. Concerning the physicochemical parameters, the incorporation of the EOs mixtures minimized the hydrophobicity of the material (θw < 65°) and modified randomly its surface free energy components (γ-; γ+; γLW). The theoretical prediction of Aspergillus sp. and Rhizopus sp. adherence to the chitosan-based films was relatively correlated to the experimental results (r = -0.601). The latter showed that 6.80 % and 19.02 % of the control film surface was covered by Aspergillus sp. and Rhizopus sp. spores, respectively. In contrast, no fungal adherence was noticed in the case of the film incorporating the triple EOs mixture. These promising results revealed that chitosan film containing C. zeylanicum, T. satureioides, and S. aromaticum EOs mixtures could be utilized as a surface coating or bioactive packaging in the food industry.

Chemical extraction, characterization, and inspection of the antimicrobial and antibiofilm activities of shrimp chitosan against foodborne fungi and bacteria.

Nowadays, the exploitation of biopolymers in the industrial sector has become a trend. Chitosan is considered one of the most investigated biopolymers due to its abundance and antibacterial, antifungal, and antibiofilm activities. In this work, chitosan was chemically extracted from shrimp shells. Solutions of HCl 1 M, NaOH 4 M, and NaOH 15 M were used for the demineralization, deproteinization, and deacetylation process, respectively. The utilized methods of characterization (FTIR, 1 H NMR, 13 C NMR, and SEC-MALS) revealed that the obtained chitosan has a moderate degree of deacetylation and low molecular weight (DDA = 74% and Mw = 72.14 kDa). The microdilution method and inoculation of solid medium were carried out to assess the antibiofilm action of chitosan against Staphylococcus aureus, Pseudomonas aeruginosa, Enterococcus hirae, Escherichia coli, Rhizopus sp., and Aspergillus sp. which are known as foodborne microorganisms. Results showed that the produced chitosan at 1 g/L inhibits between 63.44 and 99.75% of the microbial biofilm depending on the tested strains. These promising results confirm the potential deployment of the obtained chitosan in the food industry as a replacement for synthetic antimicrobial agents.

Elaboration and general evaluation of chitosan-based films containing terpene alcohols-rich essential oils.

Recently, the scientific community is interested in the synthesis of biodegradable and bioactive packaging to replace oil-based ones. Therefore, the present study aims to elaborate an active and biodegradable material using chitosan (CS-film) combined with pelargonium, tea tree, marjoram, and thyme essential oils (EOs), and then evaluate their different properties and biological activities. The obtained data showed an augmentation in CS-film thickness and opacity following the addition of EOs ranging from 17 ± 3 to 42 ± 2 µm and from 1.53 ± 0.04 to 2.67 ± 0.09, respectively. Furthermore, a significant decrease in the water vapor transmission rate and moisture content parameters was recorded as regards the treated CS-films. On the other hand, the treatment with EOs engenders random modifications in the physicochemical and mechanical characteristics of the material. Concerning the biological activities, the treated CS-films scavenged around 60% of DPPH radical while the control CS-film exhibited a negligible antioxidant activity. Finally, the CS-films containing pelargonium and thyme EOs exhibited the strongest antibiofilm-forming activity against Escherichia coli, Enterococcus hirae, Staphylococcus aureus, and Pseudomonas aeruginosa with values of inhibition greater than 70%. These encouraging results verify the effectiveness of CS-films containing EOs such as pelargonium and thyme EOs as biodegradable and bioactive packaging.

The effect of essential oils mixture on chitosan-based film surface energy and antiadhesion activity against foodborne bacteria.

In the food sector, the formation of biofilms as a result of microbial adherence on food-grade surfaces causes a major problem resulting in significant economic losses. Thereby, this work aimed to elaborate a biodegradable film using chitosan (CS-film) and reinforce its antiadhesion activity by incorporating pelargonium, clove, thyme, and cinnamon essential oils (EOs). Firstly, the antibacterial activity of these EOs alone and combined against four foodborne bacteria were analyzed by the microdilution method. Synergism was observed in the case of EOs combination. Secondly, the physicochemical characteristics and antiadhesion behavior of the CS-films were assessed by the contact angle method and ESEM, respectively. Results revealed that the EOs mixture treatment impacted considerably the physicochemical characteristics of the CS-film and reduced its qualitative and quantitative hydrophobicity. Moreover, the treated CS-film showed a strong antiadhesion behavior against Enterococcus hirae, Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus with percentages of non-covered surface equal to 97.65 ± 1.43%, 98.76 ± 0.32%, 99.68 ± 0.28%, and 95.63 ± 1.32% respectively. From all these results, the CS-film treated with the mixture of EOs presents a great potential for application as surface coating and food packaging preventing microbial adhesion and thus, avoiding food contamination and spoilage.

Assessment of the antioxidant, antimicrobial and antibiofilm activities of essential oils for potential application of active chitosan films in food preservation.

In the food industry, the development of microbial biofilms is a serious problem that leads to the contamination and deterioration of food products. To overcome that, our aim consists of searching for natural antimicrobial and non-toxic compounds (essential oils EOs), which might be used alone or adsorbed on natural biopolymer films (chitosan). In this work, the antioxidant activity of eight EOs was evaluated by DPPH radical-scavenging method while their antibacterial activity was determined by diffusion on agar and microdilution methods. Among all tested EOs, Eugenia caryophyllus, Cinnamomum zeylanicum Blume and Thymus satureioides Cosson showed high antioxidant activities at the concentration of 25.6 mg/mL, with respective values of (86.26%, 81.75%, and 76%), and strong antibacterial activity against Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, and Enterococcus hirae, with (MIC) values ≤ 4 µL/mL. At the concentration of 1 µL/mL, these EOs tested alone, showed values of antibiofilm-forming activity ranging from 79.43 to 99.33% and from 44.18 to 94.17%, when they are adsorbed onto chitosan film. These promising results confirm that these three EOs have a good potential for an eventual application in the food industry, as antimicrobial and antioxidant agents, or as active biodegradable food packaging, if combined with chitosan.

Induction of Natural Defenses in Tomato Seedlings by Using Alginate and Oligoalginates Derivatives Extracted from Moroccan Brown Algae.

Polysaccharides extracted from marine algae have attracted much attention due to their biotechnological applications, including therapeutics, cosmetics, and mainly in agriculture and horticulture as biostimulants, biofertilizers, and stimulators of the natural defenses of plants. This study aimed to evaluate the ability of alginate isolated from Bifurcaria bifurcata from the Moroccan coast and oligoalginates derivatives to stimulate the natural defenses of tomato seedlings. Elicitation was carried out by the internodal injection of bioelicitor solutions. The elicitor capacities were evaluated by monitoring the activity of phenylalanine ammonia-lyase (PAL) as well as polyphenols content in the leaves located above the elicitation site for 5 days. Alginate and oligoalginates treatments triggered plant defense responses, which showed their capacity to significantly induce the PAL activity and phenolic compounds accumulation in the leaves of tomato seedlings. Elicitation by alginates and oligoalginates showed an intensive induction of PAL activity, increasing from 12 h of treatment and remaining at high levels throughout the period of treatment. The amount of polyphenols in the leaves was increased rapidly and strongly from 12 h of elicitation by both saccharide solutions, representing peaks value after 24 h of application. Oligoalginates exhibited an effective elicitor capacity in polyphenols accumulation compared to alginate polymers. The alginate and oligosaccharides derivatives revealed a similar elicitor capacity in PAL activity whereas the accumulation of phenolic compounds showed a differential effect. Polysaccharides extracted from the brown seaweed Bifurcaria bifurcate and oligosaccharides derivatives induced significantly the phenylpropanoid metabolism in tomato seedlings. These results contribute to the valorization of marine biomass as a potential bioresource for plant protection against phytopathogens in the context of eco-sustainable green technology.