Changes in quality and microbial diversity of refrigerated carp fillets treated by chitosan/zein bilayer film with curcumin/nisin-loaded pectin nanoparticles

The quality of freshwater fish is easy to deteriorate during postmortem storage, so it is necessary to find an effective method to extend the shelf life of fish fillets. The aim of this study is mainly to develop a novel bilayer active film with curcumin/nisin-loaded pectin nanoparticles (CZ-NPs) and evaluate its effect on the quality of fish fillets. The selected sensory, physicochemical (pH, color qualities, TVB-N, TBARS, biogenic amines, moisture state) and microbial properties (microbial enumeration and high-throughput sequencing) were analyzed to confirm the preservative mechanism of films on the fillets. During storage at 4 degrees C, better sensory evaluation feedback and lower total volatile base nitrogen in the film treated samples was observed when compared to the control samples. Additionally, CZ-NPs film effectively inhibited oxidation, with the final reductions of 1.04 mg MDA/kg flesh when compared to control. As suggested by low-field NMR and magnetic resonance imaging, film treated fillets presented higher water holding capacity by controlling transformation from immobilized to free water. Meanwhile, lower microbial enumerations were also recorded in the CZ-NPs film treated group, which was reduced by a range of 1.8-2.3 log CFU/g on day 10 when compared to control. High-throughput sequencing results showed that the Pseudomonas constituted the main spoilage bacteria of fillets, and CZ-NPs film contributed to the notably suppressed growth of Pseudomonas. As a result, CZ-NPs film showed a desirable application to extend the shelf life of refrigerated flesh, as an alternative for fishery product packaging and preservation.