Document Type : Research Paper
Authors
- Fatemeh Kazemnezhad khorami 1
- sepideh Hamedi 1
- kermanian hossein 2
- Omid Ramezani 1
- Zahra Razmpour 1
- Farzaneh Havaseli.Ashtiani 3
1 Biorefinery group, Faculty of New Technologies and Aerospace Engineering of Shahid Beheshti University, Zirab Campus, Tehran, Iran
2 Head of zirab campus
3 Shahid Beheshti university
Abstract
Background and objectives: Rapid changes in lifestyle have increased the demand for processed and packaged foods. The barrier properties of packaging limit the exposure of food components to external factors, such as microorganisms, air, and light, thereby delaying food spoilage. In recent years, edible films based on natural polymers, particularly polysaccharides, have attracted considerable attention owing to their biodegradability, safety, and environmental advantages. Edible coatings form a thin protective layer on food products, helping to protect them from spoilage factors and extend their shelf life. They also offer a potential alternative to petroleum-based packaging materials and may help mitigate their associated environmental concerns. Therefore, this study aimed to investigate the effects of halloysite nanotubes (HNTs) on the properties of an edible film based on flaxseed mucilage (FM).
Methodology: Flaxseed mucilage was extracted by water soaking followed by ethanol precipitation. Biodegradable edible films based on FM were subsequently prepared using the solvent-casting and evaporation method. The effects of different HNT concentrations (1, 3, and 5 wt%) on the moisture absorption, barrier, optical, and thermal properties of the FM films were evaluated. Fourier-transform infrared (FTIR) spectroscopy was used to investigate potential interactions between FM and HNTs. The thermal stability of the films was evaluated by thermogravimetric analysis (TGA) from room temperature to 600 °C under a nitrogen atmosphere. The distribution of HNTs within the polymer matrix was qualitatively assessed by elemental mapping of Si and Al using energy-dispersive X-ray spectroscopy (EDX). Moisture absorption was determined by sequential weighing at 75% relative humidity, while water vapor permeability (WVP) was measured according to ASTM E96. The mechanical properties were evaluated according to ASTM D882. Film color parameters, including lightness (L*), redness–greenness (a*), and yellowness–blueness (b*), were determined using a colorimeter. The antibacterial activity of the films against the Gram-negative bacterium Escherichia coli and the Gram-positive bacterium Staphylococcus aureus was evaluated using the colony-counting method. Film biodegradability was also visually assessed following soil burial for 40 days.
Results: FTIR analysis showed a decrease in the intensity of the hydroxyl-associated absorption band at 3291 cm⁻¹ following HNT incorporation, suggesting possible hydrogen-bonding interactions between the hydroxyl groups of FM and the HNT surfaces. Thermal stability increased with increasing HNT content, with the 5% HNT-containing film exhibiting the highest thermal stability among the formulations investigated. EDX mapping showed an increase in the relative density of Si and Al signals with increasing HNT content, with the highest signal density observed in the film containing 5% HNT. Moisture absorption significantly decreased as the HNT content increased from 3% to 5%; among the formulations investigated, the 5% HNT-containing film exhibited the lowest moisture absorption (54.8%). WVP showed a similar decreasing trend, decreasing from 11.5 for the control film to 5.9 for the film containing 5% HNT. Increasing HNT content also improved the tensile strength of the FM films, with the 5% HNT-containing film reaching a tensile strength of 69.31 MPa. HNT incorporation altered the color characteristics of the films, as indicated by increased lightness (L*) and whiteness and decreased yellowness (b*). The antibacterial activity of the films also increased markedly following HNT incorporation. After 40 days of soil burial, the pure FM film exhibited faster apparent degradation than the HNT-containing films, while increasing HNT content delayed the apparent degradation process; the 5% HNT-containing film exhibited the slowest apparent degradation among the formulations investigated.
Conclusion: Overall, the incorporation of HNTs as a reinforcing agent improved several functional and physicochemical properties of FM-based edible films. Among the formulations investigated, the film containing 5% HNT exhibited the highest thermal stability and lowest moisture absorption, together with improved tensile strength and antibacterial activity. These findings suggest that HNT-reinforced FM films, particularly those containing 5% HNT, have potential for use in the development of biodegradable edible food-packaging materials.
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