A new active packaging film developed using electrospinning technology could offer fresh-produce packagers a multifunctional solution for controlling two major causes of postharvest deterioration: ethylene accumulation and microbial growth.
Published in Food Quality and Safety, the study by researchers at Shanghai Jiao Tong University and Inner Mongolia Mengniu Dairy combines pullulan (PUL) and polyvinyl alcohol (PVA) with titanium dioxide (TiO₂) nanoparticles and thymol (THY). The resulting nanofiber film is designed to provide photocatalytic ethylene degradation alongside antimicrobial protection.
The packaging concept addresses a limitation of conventional ethylene-control technologies. Adsorbents can have limited efficiency, while some approaches suppress ethylene activity rather than removing the gas. In the new film, anatase TiO₂ acts as a photocatalyst: when exposed to light, it generates reactive species that oxidize ethylene, ultimately converting it into carbon dioxide and water.
The researchers found that increasing the TiO₂ concentration improved ethylene-removal performance. Depending on the formulation and irradiation period, the films achieved nearly complete degradation of an ethylene concentration of 200 × 10⁻⁶. The TiO₂/THY/PUL/PVA-40 formulation achieved this within four hours, corresponding to an ethylene degradation rate of 12.5 µL/(g·h).
Packaging structure matters
Electrospinning is central to the technology. The process produces continuous nanofibers from a polymer solution under a high-voltage electric field, enabling functional nanoparticles and bioactive compounds to be distributed within the fiber network. The researchers found that the TiO₂ nanoparticles were uniformly dispersed without obvious aggregation, an important factor because nanoparticle agglomeration can reduce photocatalytic surface area and performance.
The film also demonstrated characteristics relevant to packaging applications. The TiO₂/THY/PUL/PVA film achieved a maximum tensile strength of 4.3 MPa and 43% elongation at break, providing a balance between strength and flexibility. TiO₂ contributed reinforcement, while the interaction between TiO₂ and thymol helped improve the film’s overall toughness.
Another potential packaging benefit is UV protection. The addition of TiO₂ significantly reduced UV reflectance in the 200–400 nm range, allowing the composite film to function as a UV-blocking layer while simultaneously using light to activate its photocatalytic function.
The film’s hydrophilic character also plays a role. With a water contact angle of 56.27°, the material can adsorb moisture in the high-humidity environment surrounding stored fruit. This provides water needed for the photocatalytic reactions that help convert ethylene into carbon dioxide and water.
Controlled release of the antimicrobial
Thymol provides the second active function. Rather than being used simply as a conventional preservative, it is incorporated into the nanofiber structure. Under simulated storage conditions of 4°C and 99% relative humidity, 48.81% of the thymol was released during the first 18 hours, while cumulative release reached 58.68% after seven days before reaching a plateau. This indicates that the fiber structure can influence the release profile of the active compound.
The film achieved 100% antibacterial efficiency against E. coli and S. aureus under the study conditions and also demonstrated antifungal activity against Botryosphaeria.
When tested with kiwifruit at 4°C, the active packaging extended shelf life beyond 35 days while slowing loss of firmness, color, vitamin C and anthocyanins. It also reduced weight loss, oxidative deterioration and microbial infection.
For packaging developers, the study points toward a shift from passive barriers to active, multifunctional packaging structures that interact with the package environment. The combination of ethylene removal, antimicrobial protection, UV blocking and controlled release within a lightweight nanofiber structure could have applications beyond kiwifruit, particularly for other climacteric fruits.
However, commercialization will require further work. The researchers specifically identify testing under more realistic lighting conditions, including LED sources, as an important next step. The study therefore represents a promising laboratory-scale demonstration rather than a commercially validated packaging solution.
