Development of pH-Sensitive intelligent films incorporating betacyanin from dragon fruit peel and TiO₂ nanoparticles for monitoring fish fillet freshness

This study aimed to develop novel pH-sensitive intelligent films for monitoring food freshness by incorporating betacyanin extracted from dragon fruit peel, pectin, sodium alginate, and titanium dioxide (TiO₂) nanoparticles. Pectin and betacyanin were simultaneously extracted from dragon fruit peel and combined with sodium alginate and TiO₂ nanoparticles to create composite and double-layer films. The films were comprehensively characterized to evaluate their physical, mechanical, structural, and functional properties. Additionally, their effectiveness in monitoring the freshness of mackerel fillets was assessed. The incorporation of TiO₂ nanoparticles significantly enhanced film properties, with tensile strength increasing from 3.55-13.42 MPa to 13.85–14.90 MPa, water vapor permeability decreasing from 1.58 to 3.00 × 10⁻⁹ g/msPa to 1.54–3.00 × 10⁻⁹ g/msPa, and swelling degree reducing from 294-330% to 260–261%. TiO₂ nanoparticles effectively immobilized and protected betacyanin from photodegradation, crucial for maintaining color stability. The subjected films demonstrated color changes from reddish-violet to brownish-yellow, correlating with increasing TVB-N levels in mackerel fillets. The double-layer film exhibited superior stability under both dark and light conditions compared to the composite film. This study uniquely combines dragon fruit peel-derived pectin and betacyanin with TiO₂ nanoparticles, addressing the growing demand for eco-friendly packaging solutions by utilizing food waste and developing biodegradable alternatives to synthetic pH indicators.