# Seaweed residue–derived carbon dots composite films for spoilage-responsive monitoring and preservation of large yellow croaker fillets

## TL;DR

A new packaging film made from seaweed residue and blueberry pigments can monitor fish freshness and extend shelf life.

## Contribution

A sustainable, spoilage-responsive film using seaweed-derived carbon dots and anthocyanins for intelligent food packaging.

## Key findings

- The film showed excellent mechanical and antioxidant properties with low oxygen permeability.
- It provided real-time freshness monitoring through color changes in response to pH and ammonia.
- The film effectively preserved large yellow croaker fillets for 12 days with better texture and microbial control.

## Abstract

A multifunctional packaging film was developed by incorporating blueberry anthocyanins (BA) and seaweed-residue-derived carbon dots (CDs) into a chitosan/fish gelatin (CS/FG) matrix. The CS/FG/BA/0.1CDs film exhibited well-balanced rheology, UV shielding ability, and thermal stability. It also showed improved mechanical strength, enhanced structural uniformity, lower oxygen permeability (4.14 × 10−11 g·m/(m2·s·Pa)), and superior antioxidant (ABTS: 97.15%; DPPH: 81.88%) and antibacterial activity. Importantly, the film displayed stable and visible colorimetric responses to pH (2−12) and ammonia vapor, enabling real-time freshness monitoring. When applied to large yellow croaker fillets stored at 4 °C, the film effectively delayed spoilage as indicated by reduced pH rise (6.89 ± 0.11), total volatile basic nitrogen content (28.9 ± 1.44 mg N/100 g), and microbial growth after 12 days. Treated samples also retained better texture, water-holding capacity, and sensory scores. These results demonstrate the synergistic effects of BA and CDs in supporting both preservation and intelligent monitoring, offering a sustainable packaging strategy for high-value aquatic products.

Unlabelled Image

•Carbon dots were sustainably derived from Porphyra haitanensis residues.•Carbon dots and anthocyanins were added into chitosan/gelatin hydrocolloid films.•The fabricated film showed improved physicochemical properties and bioactivities.•The film exhibited reliable colorimetric response to pH and ammonia vapor.•Carbon dots and anthocyanins synergistically promoted fish fillet preservation.

Carbon dots were sustainably derived from Porphyra haitanensis residues.

Carbon dots and anthocyanins were added into chitosan/gelatin hydrocolloid films.

The fabricated film showed improved physicochemical properties and bioactivities.

The film exhibited reliable colorimetric response to pH and ammonia vapor.

Carbon dots and anthocyanins synergistically promoted fish fillet preservation.