Colorimetric/fluorescent dual-channel pH-responsive films for the precise detection of the shrimp freshness

Current methods for monitoring food freshness often rely on single-signal outputs, which are prone to interference and lack self-validation capabilities, limiting their reliability in complex food matrices. To address this challenge, we developed a dual-channel pH-responsive composite film integrating nitrogen-doped carbon quantum dots (N-CDs) and anthocyanins within a bacterial cellulose matrix for real-time, dual-mode shrimp freshness detection. The films exhibited distinct colorimetric (brick-red to light-green) and fluorescent (non-fluorescent to bright green) transitions under varying pH conditions, driven by pH-dependent structural changes in anthocyanins and surface deprotonation of N-CDs. In shrimp trials, the dual-channel responses correlated strongly with total volatile basic nitrogen (TVB-N) levels (R² = 0.959) and pH changes, enabling precise discrimination of freshness stages over 5 days at 4 °C. The composite film demonstrated synergistic antioxidant (93.61-97.76 % radical scavenging) and antibacterial activities, while its nanofibrillar structure enhanced mechanical stability. Cross-validation between colorimetric and fluorescent signals significantly improved anti-interference capability, overcoming limitations of single-mode detection. This work establishes a portable, self-calibrating platform for real-time food quality monitoring, advancing the development of intelligent packaging systems with enhanced accuracy and multifunctionality.