Biodegradable antioxidant film composition based on chitosan

Abstract

Biodegradable chitosan-based antioxidant film composition comprising a) a chitosan matrix prepared from a 2% (w / v) chitosan solution dissolved in 1% acetic acid b) a plasticiser containing glycerol at a concentration of 1% (v / v); c) a binary combination of essential oils, including basil essential oil (BEO) and calamus essential oil (CEO), present at a concentration of 0.5% (v / v) d) a surfactant, Tween 80, added at a concentration of 0.5% (v / v) to facilitate the dispersion of the essential oils in the chitosan matrix; e) wherein the incorporation of the binary essential oils improves the mechanical properties, antioxidant activity, surface hydrophobicity and barrier properties of the film composition, making it suitable for food packaging applications.

Description

[0001] The present invention relates to the development of biodegradable antioxidant films based on chitosan, which contain a binary mixture of essential oils from basil and calamus. These films offer improved preservation properties for food packaging and biomedical applications. The invention focuses on enhancing the film functionality through natural bioactive compounds.

[0002] Biodegradable and environmentally friendly packaging materials have gained considerable attention due to increasing concerns about environmental pollution and the need to reduce the use of synthetic plastics. Among various biopolymers, chitosan is emerging as a promising alternative due to its biocompatibility, biodegradability, and natural antimicrobial properties. However, chitosan-based films often exhibit limitations in mechanical strength, barrier properties, and overall functional performance, making them less suitable for real-world packaging applications. To enhance these properties, researchers have explored the incorporation of natural additives such as essential oils, which can enhance the physicochemical properties, antimicrobial activity, and antioxidant capacity of chitosan films.

[0003] Basil essential oil (BEO), extracted from Ocimum basilicum, is known for its potent antimicrobial and antioxidant properties, making it an effective bioactive agent for active packaging. Calamus essential oil (CEO), extracted from Acorus calamus, also possesses significant bioactive properties, including antimicrobial and insect repellent activities. While several studies have focused on the integration of essential oils into chitosan-based films, the use of binary combinations of essential oils has been investigated only to a limited extent. Combining BEO and CEO in a single system offers the potential for synergistic effects, resulting in improved film functionality and enhanced performance in food packaging.

[0004] This invention aims to develop functional chitosan-based antioxidant films containing a binary blend of BEO and CEO. By leveraging the unique properties of both oils, the resulting films are expected to exhibit superior physicochemical properties, enhanced antioxidant and antimicrobial activities, and improved mechanical strength. The synergistic effects of these essential oils will contribute to the development of sustainable and active food packaging materials that provide an environmentally friendly alternative to conventional synthetic packaging while ensuring longer shelf life and better food preservation.

[0005] An object of the present disclosure is to develop a biodegradable chitosan-based film composition with improved functional properties.

[0006] Another object of the present disclosure is the incorporation of essential oils to improve the antimicrobial and antioxidant properties of the film.

[0007] Another object of the present disclosure is to provide a sustainable alternative to conventional plastic packaging materials.

[0008] Another object of the present disclosure is to improve the moisture resistance and barrier properties of the film to extend the shelf life of the product.

[0009] Another object of the present disclosure is to ensure the flexibility and mechanical strength of the film for various applications.

[0010] Another object of the present disclosure is to use environmentally friendly components, making the film safe for food and biomedical applications.

[0011] Another object of the present disclosure is to improve the dispersion and stability of essential oils in the polymer matrix.

[0012] Another objective of this disclosure is to support environmentally friendly packaging initiatives by promoting biodegradable and renewable materials.

[0013] Further objects and advantages of the present disclosure will become apparent from the following description, which is not intended to limit the scope of the present disclosure.

[0014] The present invention relates to a biodegradable chitosan-based film composition enriched with essential oils to improve its functional properties for food packaging and biomedical applications.

[0015] Another embodiment of the present invention is the use of basil essential oil (BEO) and calamus essential oil (CEO) in a binary combination to improve the antimicrobial and antioxidant properties of the film.

[0016] Another embodiment of the present invention is the incorporation of glycerin as a plasticizer to maintain flexibility while ensuring structural integrity.

[0017] Another embodiment of the present invention is the use of Tween 80 as a surfactant to improve the dispersion of essential oils in the chitosan matrix, resulting in improved film uniformity.

[0018] Another embodiment of the present invention is the preparation of the film composition by a solvent casting process followed by controlled drying to achieve a homogeneous structure.

[0019] Another embodiment of the present invention is to improve the barrier properties of the film, making it more resistant to moisture and external environmental factors.

[0020] Another embodiment of the present invention is the possible application of the film in active food packaging, which represents a sustainable alternative to synthetic plastic packaging.

[0021] Another embodiment of the present invention is the use of biopolymer materials that contribute to environmentally friendly and biodegradable packaging solutions.

[0022] The present invention relates to a biodegradable chitosan-based film composition containing essential oils to enhance its functional properties, making it suitable for food packaging and biomedical applications. The composition consists of a chitosan polymer matrix blended with glycerin as a plasticizer and a binary combination of basil essential oil (BEO) and calamus essential oil (CEO). To ensure uniform dispersion of the essential oils, a surfactant such as Tween 80 is included. The invention offers an environmentally friendly alternative to synthetic packaging materials by harnessing the antimicrobial, antioxidant, and hydrophobic properties of the essential oils while maintaining the mechanical integrity and flexibility of the chitosan film.The film is produced by a solvent casting process followed by controlled drying, resulting in a homogeneous structure with improved performance characteristics.

[0023] The present invention addresses the need for sustainable and functional biopolymer films with improved physicochemical properties, including increased mechanical strength, antioxidant potential, and water resistance. By incorporating essential oils into the chitosan matrix, the film composition benefits from improved barrier properties and bioactivity, making it ideal for extending the shelf life of perishable foods. Furthermore, the interactions between chitosan and the essential oil components contribute to structural changes that strengthen the polymer network. EXAMPLE 1: COMPOSITION'

[0024] Biodegradable chitosan-based film composition comprising: - a chitosan matrix made from a 2% (w / v) chitosan solution dissolved in 1% acetic acid - a plasticizer containing glycerin at a concentration of 1% (v / v); - a binary combination of essential oils containing basil essential oil (BEO) and calamus essential oil (CEO) at a concentration of 0.5% (v / v); - a surfactant, Tween 80, added at a concentration of 0.5% (v / v) to facilitate the dispersion of the essential oils in the chitosan matrix. EXAMPLE 2: Preparation of oil-loaded films

[0025] A 2% (w / v) chitosan solution was prepared by dissolving the biopolymer in 1% acetic acid solution and stirring for 2 hours at room temperature. 1% glycerol (v / v) was added to the chitosan solution as a plasticizer, with continuous stirring for 1 hour. The film-forming solution was then divided into two beakers labeled CBC1 and CBC2. The essential oils, including BEO and CEO, were added at a ratio of 0.5% (v / v) to the CBC2 sample, while CBC1 was retained as a control without added oil. Tween 80 was added to CBC2 as a surfactant at a concentration of 0.5% (v / v). To prepare the films, 20 ml of the solution was measured and poured into plastic Petri plates. The plates were then dried for 24 hours at a controlled temperature of 30°C.After complete drying, the film samples were carefully removed from the plates and then prepared for further analytical characterization. EXAMPLE 3: GCMS analysis of essential oils

[0026] The chemical compositions of BEO and CEO were analyzed using a gas chromatography-mass spectrometer. A 1 µL oil sample was injected with a split ratio of 1:115. The column temperature was initially maintained at 50 °C for 2 minutes, then increased to 210 °C at 3 °C / min, and then to 280 °C at 6 °C / min. Helium was used as the carrier gas at a flow rate of 1.0 mL / min, with the injector and ion source temperatures set to 260 °C and 220 °C, respectively. The primary compounds in BEO and CEO were identified by comparing the retention indices and retention times (RT) with authentic reference standards.

[0027] GC-MS analysis revealed significant differences in the chemical compositions of BEO and CEO. Estragole was the predominant compound in BEO, accounting for 48.64% of the total oil composition, and is known for its potent antimicrobial and antioxidant properties, making it valuable for food preservation and pharmaceutical purposes. CEO, on the other hand, consisted primarily of asarone (84.51%) with a retention time of 31.655 minutes, which possesses neuroprotective potential but also raises toxicological concerns at higher concentrations. Furthermore, BEO contained significant amounts of linalool, which contributes to its antioxidant, antimicrobial, and aromatic properties. EXAMPLE 4: Thickness and mechanical properties of the films

[0028] The thickness of the CBC1 and CBC2 films was measured using a digital micrometer, taking five random measurements per sample to determine the average thickness. Mechanical properties were evaluated using a standard universal tester with a 5 kg load cell. The films were preconditioned for 40 hours at 25 °C and 50% relative humidity, cut into 7 × 60 mm strips, and tested at a speed of 30 mm / min to determine tensile strength (TS, MPa) and elongation at break (EAB, %). The average values ​​were calculated using the Exponent Connect software platform.

[0029] The thickness of the chitosan-based films (CBC1 and CBC2) was evaluated to determine the structural effects of the incorporated essential oil. The control film (CBC1) had an average thickness of 0.114 ± 0.008 mm, while the oil-loaded film (CBC2) showed a slight increase to 0.128 ± 0.010 mm. This increase is likely due to the presence of essential oils, which may have increased the molecular interactions and density of the polymer network, affecting the film-forming properties.

[0030] Significant differences were observed between the films in terms of mechanical properties, which are crucial for packaging and biomedical applications. The tensile strength (TS) of CBC1 was measured at 0.02 ± 0.003 MPa, while CBC2 exhibited a higher TS of 0.029 ± 0.002 MPa.

[0031] Despite the increase in tensile strength, the elongation at break (EAB), an indicator of film flexibility, remained largely unchanged between CBC1 (127.15 ± 6.85%) and CBC2 (128.95 ± 3.26%). This suggests that the incorporation of essential oils improved the strength of the films but did not affect their flexibility. EXAMPLE 5: Light transmittance and turbidity value

[0032] The transmittance and turbidity values ​​of the CBC1 and CBC2 film samples were measured using a turbidity meter. For analysis, the film samples were carefully placed in the device, ensuring correct orientation to avoid measurement errors.

[0033] The visual inspection of the chitosan-based films was an important parameter to determine the structural integrity of the films, which are suitable for further applications such as, e.g., packaging. While the control film (CBC1) had a transparent and homogeneous surface, the oil-loaded film (CBC2) was somewhat less transparent, which is probably due to the internal dispersion of small oil droplets in the polymer matrix.

[0034] Furthermore, the transmittance of CBC1 was significantly higher (89.3%) than that of CBC2 (84.74%), suggesting that the addition of essential oil caused reduced film transparency. This phenomenon is consistent with previous findings of reduced film transmittance due to oil-polymer interactions in oil-containing films. The haze value of CBC2 (51.27%) increased compared to CBC1 (11.47%), indicating greater light scattering with unevenly distributed oil droplets. EXAMPLE 6: Antioxidant analysis of the films

[0035] The antioxidant potential of the films was evaluated by measuring their DPPH scavenging activity. The reaction mixture was prepared and analyzed using an ONDA-Vis spectrophotometer at a wavelength of 517 nm. The results, expressed as percent inhibition, were derived from the average of three independent measurements for each sample.

[0036] The results show that the antioxidant activity of the films increased significantly from 32.116 ± 1.395 for the control film (CBC1) to 64.505 ± 0.738 for the oil-loaded film (CBC2). This improvement may be due to the presence of bioactive compounds with antioxidant activity in BEO and CEO. It has also been reported that the incorporation of essential oils into chitosan films increases the antioxidant capacity due to the presence of phenolic compounds and terpenoids. Furthermore, the antioxidant mechanism of the films may be related to the synergistic effects of the essential oils and chitosan. EXAMPLE 7: Hydrophobicity of the surface

[0037] The water contact angle was measured using a goniometer to assess the surface hydrophobicity of the CBC1 and CBC2 films. The film samples were cut into 2 × 2 cm pieces and placed on a flat surface of the analyzer. Each film was then mounted, and a single water droplet (1 µl) was carefully placed in the center of the film using a precision micropipette. The contact angle was calculated using dpiMAX software, which allowed for a quantitative determination of the surface hydrophobicity of the films.

[0038] The results show that the control films (CBC1) exhibited a lower contact angle of 69.77°, indicating a more hydrophilic surface, while the oil-impregnated film (CBC2) exhibited a higher contact angle of 82.40°, indicating increased hydrophobicity. This change in behavior can be attributed to the hydrophobic nature of the essential oil components, which reduced the film's affinity for water. The results suggest that the incorporation of essential oils increases the water resistance of the film, making it more suitable for food packaging by preventing moisture penetration and thus extending the shelf life of food. EXAMPLE 8: FTIR analysis

[0039] FTIR spectroscopy was performed with a spectrometer for further characterization of the chemical interactions between the biopolymer and the oil matrix. The spectral recordings (4000-400 cm- 1 ) reflect the molecular interactions and the details of the functional groups of the films.

[0040] The results show that the FTIR spectra of CBC1 (control film) and CBC2 (oil-loaded film) have characteristic peaks that are associated with functional chitosan groups. The control film (CBC1) showed a broad peak around 3400 cm- 1, which corresponds to the OH stretching, indicating hydrogen bonding within the chitosan matrix. The incorporation of essential oils into CBC2 resulted in a slight shift and broadening of this peak, indicating enhanced hydrogen bonding between chitosan and essential oil components. Furthermore, the FTIR spectra showed peaks at 1640 cm- 1 (C=O stretching, amide I) and 1550 cm- 1 (NH bend, amide II), which are characteristic of the amide bond of chitosan. The reduction in the intensity of these peaks in CBC2 indicates possible interactions between chitosan and the bioactive components of the essential oils, leading to structural changes in the polymer matrix. EXAMPLE 9: Statistical Analysis

[0041] Data are expressed as mean ± standard deviation (SD) of triplicate determinations. Statistical significance was determined using one-way ANOVA and Fisher's post hoc test. Examples

[0042] 1. A biodegradable chitosan-based film composition comprising: a) a chitosan matrix prepared from a 2% (w / v) chitosan solution dissolved in 1% acetic acid b) a plasticiser containing glycerol at a concentration of 1% (v / v); (c) a binary combination of essential oils containing basil essential oil (BEO) and calamus essential oil (CEO) at a concentration of 0.5% (v / v); d) a surfactant, Tween 80, added at a concentration of 0.5% (v / v) to facilitate the dispersion of the essential oils in the chitosan matrix

Claims

[1] Biodegradable chitosan-based antioxidant film composition comprising a) a chitosan matrix prepared from a 2% (w / v) chitosan solution dissolved in 1% acetic acid b) a plasticiser containing glycerol at a concentration of 1% (v / v); c) a binary combination of essential oils, including basil essential oil (BEO) and calamus essential oil (CEO), present at a concentration of 0.5% (v / v) d) a surfactant, Tween 80, added at a concentration of 0.5% (v / v) to facilitate the dispersion of the essential oils in the chitosan matrix; e) wherein the incorporation of the binary essential oils improves the mechanical properties, antioxidant activity, surface hydrophobicity and barrier properties of the film composition, making it suitable for food packaging applications. [2] The biodegradable chitosan-based antioxidant film composition of claim 1, wherein the film composition has an increased tensile strength with a tensile strength of at least 0.029 ± 0.002 MPa compared to a control film without essential oils. [3] The biodegradable chitosan-based antioxidant film composition according to claim 1, wherein the elongation at break (EAB) between the control film and the oil-loaded film remains unchanged, showing consistent flexibility. [4] The biodegradable chitosan-based antioxidant film composition according to claim 1, wherein the film composition has an enhanced antioxidant activity with a DPPH scavenging percentage of at least 64.505 ± 0.738%. [5] The biodegradable chitosan-based antioxidant film composition according to claim 1, wherein the surface hydrophobicity is increased as evidenced by a contact angle of at least 82.40°, thereby improving water resistance for food packaging applications. [6] The biodegradable chitosan-based antioxidant film composition according to claim 1, wherein the transmittance of the film composition is reduced to 84.74% compared to the control, with a turbidity value of at least 51.27%, indicating structural changes due to the dispersion of essential oil droplets. [7] A biodegradable chitosan-based antioxidant film composition according to claim 1, wherein the FTIR analysis shows shifts of the characteristic chitosan peaks, including a broadening at 3400 cm- 1, indicating enhanced hydrogen bonding interactions between chitosan and essential oils. [8] A biodegradable chitosan-based antioxidant film composition according to claim 1, wherein the film composition is prepared by solvent casting with drying at a controlled temperature of 30°C for 24 hours to ensure uniform distribution of the essential oils in the polymer matrix.