PSI - Issue 68

Krastena Nikolova et al. / Procedia Structural Integrity 68 (2025) 845–853 K. Nikolova et al. / Structural Integrity Procedia 00 (2025) 000–000

846

2

hydrocolloids, such as carbohydrates, gums, and proteins (Paidari et al., 2021). To enhance the physical, chemical, and mechanical properties or improve the functionality of these films, plasticizers (such as glycerol), crosslinking agents, emulsifiers, reinforcements, or lipids (especially waxes and essential oils) are often incorporated into the biopolymer matrix (Kong et al., 2022). Edible coatings act as a barrier between food and the environment, reducing oxygen and moisture exposure. By limiting these exchanges, they help decrease water loss, oxidation, and respiration rates, which in turn extends the shelf life of food products (Chhikara & Kumar, 2022). Recent studies highlight increasing interest in polysaccharide-based edible coatings combined with essential oils (EOs) for their strong antioxidant and antimicrobial properties (Singh et al., 2008). Common polysaccharides like chitosan, pectin, alginate, and gellan are favored due to their ease of extraction and wide availability from inexpensive sources such as grains, vegetables, and fruits (Parreidt et al., 2018). However, the hydrophilic nature of these coatings limits their use for certain food products. Chitosan, a deacetylated form of chitin, is a linear amino polysaccharide with D-glucosamine and N-acetyl-D glucosamine units (Wang et al., 2018). It is commonly used in edible film production due to its broad antimicrobial activity, non-toxicity, biocompatibility, biodegradability, and solubility in acids, which enable its film-forming properties. Pure chitosan-based films are resistant to the breaking strength and the addition of glycerol resulted in a higher percentage of elongation at break (Escárcega-Galaz et al., 2018). Cellulose is a widely available and sustainable biopolymer found in large quantities in the natural world. It can be sourced from diverse materials such as wood, cotton, agricultural waste, and even bacteria (Zhao et al., 2019). Chemical processes can modify cellulose into various forms like HPC, CMC, HPMC, MC, or EC, each with specific properties. These cellulose derivatives are popular in edible film production because of their biodegradability, strong mechanical properties, and environmental sustainability (Panahirad et al., 2021). Pectin, a soluble component of plant fiber found in fruits and vegetables, is a heterogeneous acidic polysaccharide composed of β-1,4-linked D-galacturonic acid residues (Freitas et al., 2021). It exists in two forms, High Methoxyl Pectin (HMP) and Low Methoxyl Pectin (LMP), which differ in their levels of methyl esterification of the carboxyl groups on galacturonic acid residues (Christensen, 2020). While pure pectin films are clear and homogeneous, they offer poor moisture barrier properties (Galus and Lenart, 2013). Alginate, a natural polysaccharide derived from brown algae like Macrocystis and Laminaria, is valued for its low toxicity and chemical versatility. Its colloidal properties—such as thickening, stabilizing, and film-forming - make it ideal for edible film production (Mahcene et al., 2020). Alginate-based films help improve food quality and shelf life by reducing dehydration, controlling respiration, and acting as oxygen barriers, which delay lipid oxidation and microbial growth. Since most polysaccarides are hydrophilic, their physical and mechanical properties are affected by water. As a result, reducing the water sensitivity of these films to enable their use with high-moisture, perishable foods is an area of significant research. Common approaches to address this issue include crosslinking biopolymers or incorporating hydrophobic compounds like lipids into the film formulation, strategies that have been successfully implemented by various researchers (Kong, 2022). Essential oils(EOs), aromatic oily liquids extracted from plant materials, are among the most commonly used lipids because of their hydrophobic, antioxidant and antimicrobial properties. The present research aims to compare the structural and mechanical properties of pure and tea tree oil loaded films from chitosan, pectin, alginate and HPMC. 2. Materials and methods 2.1. Materials Chitosan hydrochloride from fungal origin, which is water soluble, was used in the current research. It was purchased from Glentham life sciences Ltd. (Corsham, UK) and was used as delivered. It is characterized with viscosity (1% in water, 20 °C) 10–120 cps and degree of deacetylation >85%. Tween 20, DPPH (2,2-diphenyl-1 picrylhydrazyl), Sodium alginate, and Hydroxypropyl methylcellulose (HPMC) were bought from Sigma-Aldrich (Taufkirchen, Germany). Classic AM 901 pectin with Galacturonic acid content 82 % and degree of esterification 38 % was delivered from Herbstreith & Fox GmbH & Co. KG (Germany). The tea tree oil was bought from dōTERRA(Ireland). All other chemicals were of analytical grade.