The preservation effects of chitosan copolymers (gallic acid and protocatechuic acid) on sea bass (Lateolabrax japonicus) fillets

This study was aimed at preparing chitosan (CS)-phenolic acids copolymers to obtain better preservation effect in marine products. In this work, CS was grafted onto phenolic acids such as gallic acid (GA) and protocatechuic acid (PA) by a carbodiimide coupling method. The copolymers (CS-grafted-GA (CS-g-GA) and CS-grafted-PA (CS-g-PA)) were further confirmed through physicochemical properties including ultraviolet–visible (UV–Vis) spectrophotography, fourier transform infrared (FTIR) spectrometry, differential scanning calorimetry (DSC) thermogram, rheological behaviour, scanning electron microscope (SEM) and antioxidant activity analysis. Subsequently, the effects of copolymers on preservation of refrigerated sea bass (Lateolabrax japonicus) fillets were investigated. The results showed that the CS-g-GA (110.82 mg GA/g) exhibited higher grafting rate than CS-g-PA (62.63 mg PA/g). According to the assessment of UV–Vis and FTIR spectrometry, both the GA and PA were grafted onto CS successfully. SEM analysis demonstrated that the microstructure of copolymers became irregular. Meanwhile, both the CS-g-GA and CS-g-PA copolymers displayed superior thermal stability, rheological properties and antioxidant capacity than the pure CS. Furthermore, the copolymers also revealed a significantly stronger preservation effect on sea bass fillets including inhibiting microbial growth and delaying the deterioration of color, texture and sensory quality. Therefore, CS-g-GA and CS-g-PA could be used as promising preservatives for seafood.