L-cysteine modified carboxymethyl chitosan composite film: sustained release of cinnamon essential oil, enhanced antibacterial properties, and application in shrimp preservation

To extend shrimp shelf life during storage, a composite film incorporating cinnamon essential oil (CEO) was developed, composed of oxidized hyaluronic acid and thiol-modified carboxymethyl chitosan. The results showed that the CEO was stably encapsulated within the composite film (OSC) and formed OSC-CEO, and its elongation at break and puncture strength increased to 59.83 % and 5.89 kg/mm 2 , respectively. Meanwhile, the film loaded with 7 % CEO achieved a water vapor permeability of 7.14 × 10 −12  g/m·s·Pa and an oxygen permeability of 16 × 10 −9  g/m 2  s. Under reducing conditions, the cleavage of disulfide bonds in the film reduces the network density and accelerates the release of CEO. Moreover, the film containing 7 % CEO achieved an effective loading rate of 80.53 % and maintained sustained release over 42 h. This controlled-release mechanism results in potent antibacterial activity and oxidation resistance. Compared with the unpackaged group, the 7 % CEO treatment group exhibited better preservation during the shrimp storage. The OSC-7 % CEO film-coated shrimp showed a weight loss (10.54 %), TVB-N content (27.55 mg/100 g), MDA content (0.51 mg/100 g), TVC (4.88 log CFU/g), and ORP (−49.51 mV). This novel composite material offers a new approach to active food packaging, and it has broad applications in shrimp storage.