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pH-responsive imine-chitosan-based intelligent controlled-release packaging films with transformable antimicrobial modes from defense to attack

Summary

Researchers developed a smart food packaging film that fights bacteria and fungi in two different ways depending on acidity levels. When stored with neutral pH foods, the film’s surface prevents microbes from sticking to it. When the food becomes more acidic (like in tomato juice), the film releases antimicrobial compounds that actively kill the microorganisms. Tests showed it effectively preserved cherry tomatoes and tomato juice while blocking harmful UV light.

Background

Antimicrobial active packaging is crucial for extending food shelf life, but developing intelligent and responsive antimicrobial strategies remains desirable. Traditional approaches using either active release or passive contact strategies have limitations in durability and effectiveness over time.

Objective

To design a pH-responsive chitosan film decorated with 2-hydroxy-4-methoxybenzaldehyde (HMB) that can switch antimicrobial modes from defense to attack based on environmental pH changes. The film aims to provide both contact-based anti-adhesion and release-based antimicrobial properties.

Results

HDCF exhibited excellent antifungal adhesion against P. citrinum, P. chrysogenum, and A. niger, and antibacterial adhesion against S. aureus before HMB release. Under acidic conditions (pH 4), HDCF showed enhanced release-antimicrobial activity with 100% fungal inhibition against A. niger and 4.13 log reduction of S. aureus. The film demonstrated strong UV barrier properties and preserved cherry tomatoes and tomato juice effectively.

Conclusion

HDCF provides a novel intelligent antimicrobial packaging strategy with transformable modes from defense to attack via pH stimulation. The film shows excellent storage stability, UV shielding properties, and practical effectiveness in food preservation, offering new possibilities for next-generation food packaging applications.
  • Published in:Food Chemistry X,
  • Study Type:Experimental Research,
  • Source: PMID: 41080136, DOI: 10.1016/j.fochx.2025.103087
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