Enhanced microbial safety of channel catfish (Ictalurus punctatus) fillet using recently invented medium molecular weight water‐soluble chitosan coating

Chitosan with higher molecular weight exhibited higher antimicrobial efficacy against foodborne pathogens. However, the poor water solubility of higher or medium molecular weight chitosan limits its applications. To overcome the challenge, our research team searched for simple preparation procedure for fast‐dissolving medium molecular weight chitosan in water. Throughout the process, we were able to obtain a higher concentration of medium molecular weight water‐soluble (MMWWS) chitosan (400 kDa). The MMWWS chitosan showed physicochemical properties that are suitable for edible coating. Antibacterial activities of 400‐kDa chitosan coating prepared in acetic acid (1% v/v) or aspartic acid (1% or 3% w/v) were examined. The surface of catfish cubes was inoculated with six foodborne pathogens and then coated with chitosan solutions. The survival of each pathogen was evaluated during shelf life storage. Compared with the control, 3% w/v chitosan coating in aspartic acid solution exhibited the most effective antibacterial activities among other coating treatments, completely inhibiting Vibrio parahaemolyticus on the surface of catfish. The study suggested that chitosan dissolved in aspartic acid has the potential for use as an alternative antimicrobial coating for catfish fillet. Significance and Impact of the Study: Channel catfish is one of the primary harvestable and freshwater fish species. However, they are susceptible to microbial contamination and spoilage during processing and storage. This study proposed an innovative risk mitigation strategy by applying an edible chitosan coating. Using our novel technique (patent pending) to produce medium molecular weight water‐soluble chitosan, 3% w/v chitosan coating prepared in aspartic acid solution exhibited the most effective antibacterial activities. The finding of this study can be utilized to enhance the microbial safety of catfish.