The effects of polylactic acid-whey protein isolated bi-layer film incorporated with ZnO nanoparticles on the quality of common carp Cyprinus carpio

This study investigates the effect of PLA (Polylactic acid)-whey protein isolated (WPI) in combination with ZnO nanoparticles (ZnONPs) on the quality of common carp (Cyprinus carpio) fillets stored at 4 ± 1 °C in terms of the bacterial (total mesophilic count (TMC) and psychrotrophic count (PTC)), physicochemical characteristics (total volatile basic nitrogen (TVB-N), pH, thiobarbituric acid (TBA), peroxide value (POV), and biogenic amines), and sensory scores. The fillets were randomly divided into four lots and subjected to the following treatments by wrapping: control, polylactic acid (PLA), PLA-WPI, and PLA-WPI/ZnONPs. PLA-WPI demonstrate a synergistic effect in retarding bacterial growth when used in combination with ZnONPs compared to others (P < 0.05). Results indicated that the lowest TVB-N (36.40 mg N/100 g), pH (7.28), TBA (1.24 mg malonaldehyde/kg sample), POV (0.19 meq/kg of fish lipid) were obtained in fillets wrapped with PLA-WPI containing ZnONPs at the end of storage. During storage, the histamine (HIS), putrescine (PUT), and cadaverine (CAD) levels decreased in the control and treated samples. The fillets treated with PLA-WPI containing ZnONPs had the best sensory characteristics. An extension of the shelf-life of fillets wrapped with PLA-WPI/ZnONPs (up to 12 days) was attributed to the antioxidant and antimicrobial characteristics of WPI and ZnONPs. These results confirmed that incorporating ZnO into PLA-WPI films could improve the efficiency of film packaging system in protecting of fish fillets from spoiling.