Chitosan/hydroxypropyl - β - cyclodextrin dual responsive biodegradable film achieves controlled release of citral, extending the shelf life of cherry tomatoes by 4-10 days

The research team used chitosan as the matrix and hydroxypropyl – β – cyclodextrin (HP β CD) as the inclusion carrier to construct a composite membrane system called CCPH. Unlike conventional single response controlled release systems, the active ingredient citral (CIT) is fixed in two forms simultaneously in the membrane: one is covalently anchored to chitosan through dynamic imine bonds, and the other is non covalently encapsulated through HP β CD cavities. This “double lock” structure allows the release behavior to no longer rely on passive diffusion, but be triggered by environmental signals in coordination. The release experiment showed that under neutral and moderate humidity conditions (pH 7, 43% RH), the cumulative release rate of citral was controlled within 7.88% ± 0.19%; In the acidic high humidity environment (pH 4, 98% RH) that simulates fruit decay, the hydrolysis of imine bonds and network expansion work together to significantly trigger the release of citral. This mechanism provides a verifiable design path for on-demand release of packaging materials in a real corrupt microenvironment.

Antibacterial, preservation, and degradation performance

In actual preservation testing, the optimized CCPH15 film extended the shelf life of cherry tomatoes by 4-10 days.

. The antibacterial evaluation showed that the inhibition rate of the membrane against Escherichia coli and Staphylococcus aureus reached 99.97%. In terms of degradation performance, the soil degradation rate of the material within 10 days is 42.37% ± 1.76%, reflecting the potential application of biodegradable packaging materials in food preservation scenarios.

Significance for polymer additives and packaging materials industry

The value of this research lies in advancing packaging functionality from passive barrier to environmentally responsive controlled release.

. For food contact packaging, the migration and release behavior of active ingredients is directly related to safety and effectiveness. The dual response design establishes a clear data boundary between low release background and high release trigger, providing a reference release curve idea for formula development. At the processing level, chitosan based composite films require film formation processes and stability. Processing stability is a key link for this type of active film to move from laboratory to large-scale production. Antioxidants and other additives are often used in similar active packaging systems to protect sensitive active ingredients and matrix resins, but this study did not involve the use of antioxidants, and related formula extensions need to be verified separately. In addition, the film is mainly composed of biodegradable biobased materials, complementing the current trend of packaging sustainability that combines recycled and recyclable designs. Biodegradable active films are suitable for specific preservation scenarios, while the recycled material system focuses on closed-loop recycling, forming a technological combination of carbon reduction and functionalization of packaging materials. In terms of food contact compliance, the study did not report migration tests or regulatory compliance data, which is a testing step that needs to be completed before the commercialization of this type of active film.

Issues to be clarified

This study did not disclose the specific ratio, film thickness, and mechanical properties data of chitosan and HP β CD, nor did it provide results of food contact migration tests and sensory evaluations.

. The safety of residues and by-products after the release of citral, the processing stability window of large-scale film-forming technology, and its universality in different fruit and vegetable categories still need further research and verification.

Information source:Humidity‐pH Dual‐Responsive Biodegradable Films Based on Chitosan/Hydroxypropyl‐β‐Cyclodextrin for Controlled Citral Release and Cherry Tomato Preservation， Organized by Herun Chemical.