Abstract
To improve the antibacterial and antioxidant properties of chitosan (CS), CS grafted with gallic acid (GA) using recombinant bacterial laccase from Bacillus vallismortis fmb-103 (fmb-rL103) as a catalyst. The structures of grafted chitosans were identified using Fourier transform infrared spectroscopy (FT-IR) and UV visible spectrum (UV–Vis spectroscopy). After gallic acid grafting, the antibacterial properties of chitosans against Pseudomonas, Acinetobacter, Brochothrix thermosphacta, Escherichia coli, Staphylococcus aureus, Salmonella, and Listeria monocytogenes were significantly improved. Meanwhile, 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging results showed that the antioxidant properties of grafted CS increased as well. The preservative effects of the grafted chitosan on chilled meat were then investigated. For this purpose, the quality indexes of the chilled meat during the storage were monitored, including total bacterial count, total basic volatile nitrogen (TVB-N) content, pH value, color and thiobarbituric acid reactive substances (TBARS) and so on. The results showed that coating with the grafted chitosan retarded the growth of spoilage bacteria, and decreased TVB-N and TBARS values of meat. The shelf life of chilled meat coated by CS grafted with GA (GA-g-CS) also extended from 6 days to 18 days at 4°C. These results provided a theoretical basis for the future application of the GA-g-CS in the preservation of chilled meat.Highlights: (1)The temperature and pH-stable bacterial laccase was used to synthesize gallic acid grafted chitosan.(2)Antioxidant and antibacterial properties of chitosan were improved through grafting gallic acid.(3)Storage properties of chilled meat were improved by coating with gallic acid grafted chitosan.
Highlights
Chitosan (CS) is a good substance for food preservation due to its non-toxic, biodegradable, biocompatible and antimicrobial features
The results showed that coating with the grafted chitosan retarded the growth of spoilage bacteria, and decreased TVB-N and thiobarbituric acid reactive substances (TBARS) values of meat
The shelf life of chilled meat coated by CS grafted with gallic acid (GA) (GA-g-CS) extended from 6 days to 18 days at 4◦C. These results provided a theoretical basis for the future application of the GA-g-CS in the preservation of chilled meat
Summary
Chitosan (CS) is a good substance for food preservation due to its non-toxic, biodegradable, biocompatible and antimicrobial features. Electrostatic interactions with other compounds can be established if these functional groups protonated (Liu et al, 2012). Natural phenolic, such as chlorogenic acid, ferulic acid, caffeic acid, and gallic acid, are good candinates to be grafted with CS backbones (Cirillo et al, 2016). There were four types of grafting techniques, such as free radical mediated grafting, carbodiimide based coupling, enzyme-catalyzed grafting and electrochemical methods, have been developed to graft phenolic groups onto CS (Liu N. et al, 2018). Enzyme-catalyzed grafting method is more eco-friendly and much safer than chemical coupling method (Aljawish et al, 2014)
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