Document Type : Research Article
Authors
1 M. Sc. Graduated of the Department of Food Science and Technology, Fasa Branch, Islamic Azad University, Fasa, Iran
2 Department of Food Science and Technology, Faculty of Agriculture, Fasa Branch, Islamic Azad University, Fasa, Iran.
Abstract
Introduction: Scientific evidence is mounting that synthetic chemicals used as food additives may have harmful impacts on health and the biological system and cause many diseases and damages to the human body. Also, many consumers are concerned about the use of artificial ingredients to maintain the quality and safety of foods. Therefore, the use of natural preservatives and food preservation methods based on natural compounds have attracted the attention of researchers. Edible films and coatings are useful materials, mainly produced from biodegradable polymers including polysaccharides (gums), proteins, and lipids, and are commonly used for the shelf life extension of foods. The primary edible films /coatings are promising alternative methods to preserve, and retard the adverse chemical reactions and microbial growth. They also can act as a carrier of antimicrobials, antioxidant substances, and other additives. Sage seed gum (SSG) is a water-soluble polysaccharide obtained from Sage (Salvia macrosiphon). It is an environmentally-friendly biodegradable material that can form high-viscosity aqueous solution and exhibit pseudoplastic behavior. Essential oils (EOs) are volatile and aromatic oily liquids extracted from various plants. Most of the EOs have antimicrobial and antioxidant activities due to their phenolic compounds, terpenes and terpenoids. A promising technique is incorporating EOs into coating solutions as active film/coating to extend the shelf life of food products. Bay leaf (Laurus nobilis) is an aromatic evergreen tree or large shrub with green, glabrous leaves. It is used as a flavoring agent and an essential ingredient in food preparation. Bay leaf has received much attention due to its antimicrobial, antioxidant, anti-inflammatory and immune system stimulating properties. Hence, the aim of the present study was to evaluate the antimicrobial and antioxidant properties of SSG coating incorporated with different concentrations of bay leaf EO (BLEO) and its nanoemulsion (NEO).
Materials and methods: The active packaging was produced based on the gum of sage seed containing BLEO and BLNEO. After preparing the EO from bay leaves, their corresponding NEO was produced and the characterization of nanoparticles was evaluated in terms of droplet size, polydispersity index (PDI) and zeta potentials. Then, the antimicrobial and antioxidant properties of BLEO and BLNEO were compared. After that, SSG coatings were prepared with 1.5% and 3% BLEO and their corresponding NEO forms. Subsequently, the antioxidant (DPPH and ABTS) and antimicrobial (against Bacillus cereus, and Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli) properties of the produced films were investigated.
Results and discussion: Gas chromatography-mass spectrometry (GC-MS) identified 1,8-Cineole and α - Terpinyl acetate as the major components of BLEO. The NEO exhibited a droplet size of approximately 92.4 nm and a zeta potential of -45.1 mV. In comparison to the control and SSG, it was found that the group comprising EO and NEO significantly (p<0.05) showed superior free radical scavenging capacity. SSG-3% BLNEO had the highest DPPH inhibition percentage (69.54%). According to the results obtained, EO at the nanoscale can scavenge more free radicals than EO (p<0.05). Antimicrobial inhibition zone of different treatments against selected gram positive and gram negative bacteria showed that all bacteria were strongly inhibited after the addition of BLEO into the SSG. Moreover, data revealed that the growth of the studied pathogens was completely inhibited in a dose-dependent manner (p<0.05). SSG-BLNEO exhibited better antimicrobial activity than SSG-BLEO coating and its antimicrobial activity was significantly enhanced by increasing BLNEO concentration (p<0.05). This phenomenon is attributed to the protective role of encapsulation and the slow release of EO from the coating matrix, resulting in enhanced antimicrobial activity. Nanoemulsions, owing to their small droplet size and high surface area, offer superior efficacy compared to conventional emulsions. Consequently, the gradual release of essential oils from nanoemulsion-based edible coatings contributes to their enhanced antimicrobial performance.
Conclusion: These findings suggest that the SSG-BLNEO edible active coating possesses promising applications as an antimicrobial and antioxidant agent for food packaging applications.
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