Pulsed ultrasound–induced montmorillonite/pectin composite film with an interlocking structure for strawberry packaging

Pulsed ultrasound technology can effectively enhance the dispersion of nanofillers in pectin-based films. However, its cavitation effect often degrades the pectin matrix, making it difficult to balance filler dispersion with structural integrity. Therefore, this study breaks through the traditional “matrix-inert filler” research paradigm by utilizing pulsed ultrasound as a dynamic modulation tool to actively regulate the interfacial assembly between montmorillonite (MMT) and pectin. Composite films of pectin and MMT with different pulsed ultrasound treatment durations (U-(U10-MMT)/P) were prepared and structurally characterized. The results indicate that appropriate ultrasonic treatment effectively promotes the dispersion and interlayer expansion of MMT while largely preserving the structural integrity of pectin molecules. This process induces crosslinking between pectin molecular chains and MMT via hydrogen bonding and other noncovalent interactions, resulting in an intercalation effect, ultimately forming a well-interlocking MMT–pectin network in the film. This structure considerably enhances the tensile strength (30.89 MPa), elongation at break (9.94%), and UV-shielding capability, and reduces water vapor permeability of U10-(U10-MMT)/P. Consequently, the U-(U10-MMT)/P film demonstrates promising potential for fruit packaging applications. This study establishes an effective processing window for preparing pectin-based films using pulsed ultrasound, and reveals the formation mechanism of the MMT–pectin interlocking network induced by this technique. It further clarifies the performance-enhancing role of this structure, providing an effective strategy for reinforcing pectin-based fruit packaging.