Work

Design of responsive films using phenylurea modified chitosan and Viburnum tinus L. extract as natural indicator

Year: 2026

Type: article

Abstract: Chitosan (Cs) films are attractive for sustainable packaging due to biodegradability and intrinsic antimicrobial activity, yet their barrier and mechanical performances are often insufficient for demanding applications. Here, we report a two-step strategy combining covalent phenylurea grafting on chitosan (Cs-PU) with the incorporation of a Viburnum tinus L. fruit ethanolic extract (VTE) as a natural, pH-responsive indicator. Phenylurea grafting was designed to introduce strong, directional intermolecular interactions within the polymer matrix and led to marked improvements in film performance: compared with pristine Cs, Cs-PU showed ∼25% higher tensile strength, a higher surface hydrophobicity (water contact angle: 81.8° → 101.2°), and a lower water vapor permeability (3.5 → 2.6 × 10⁻¹¹ g·m⁻¹·s⁻¹·Pa⁻¹). VTE, not previously reported as an additive for biopolymer film modification, endowed the films with pH-responsive optical functionality, producing a clear and reversible color shift over pH 0–14, while maintaining good structural and barrier properties. As a proof-of-concept application, Cs-PU@VTE films were used as headspace indicator labels for Atlantic cod (Gadus morhua): the labels exhibited rapid and sensitive colorimetric responses to spoilage-related volatile amines, with visible changes within 24 h at room temperature, enabling real-time freshness monitoring. Overall, this work demonstrates an integrated approach to obtain bio-based films that combine improved mechanical/barrier properties with smart colorimetric functionality for potential packaging applications.

Source: Carbohydrate Polymer Technologies and Applications

DOI: 10.1016/j.carpta.2026.101103