Effects of Antimicrobial Coatings and Cryogenic Freezing on Survival and Growth of Listeria innocua on Frozen Ready-to-Eat Shrimp during Thawing


Direct inquiries to author Jin (E-mail: tony.jin@ars.usda.gov).


Foodborne pathogens such as Listeria monocytogenes could pose a health risk on frozen ready-to-eat (RTE) shrimp as the pathogen could grow following thawing. In this study, antimicrobial-coating treatments alone, or in combination with cryogenic freezing, were evaluated for their ability to inhibit the growth of Listeria innocua, a surrogate for L. monocytogenes, on RTE shrimp. Cooked RTE shrimp were inoculated with L. innocua at 3 population levels and treated with coating solutions consisting of chitosan, allyl isothiocyanate (AIT), or lauric arginate ester (LAE). The treated shrimp were then stored at –18 °C for 6 d before being thawed at 4, 10, or 22 °C for either 24 or 48 h. Results revealed that antimicrobial coatings achieved approximately 5.5 to 1 log CFU/g reduction of L. innocua on RTE shrimp after the treatments, depending on the inoculated population levels. The coating-treated shrimp samples had significantly (P < 0.05) less L. innocua than controls at each thawing temperature and time. Cryogenic freezing in combination with coating treatments did not achieve synergistic effects against L. innocua. Antimicrobial coatings can help to improve product safety by reducing Listeria on RTE shrimp.

Practical Application

Frozen ready-to-eat (RTE) shrimp are precooked. They are allowed to thaw and are then consumed without further heat treatment. Therefore, they would pose a higher health risk if contaminated with foodborne pathogens such as Listeria monocytogenes. Antimicrobial coatings provide an additional barrier to reduce Listeria on RTE shrimp during thawing and storage, and can be used by the seafood industry and distributors to enhance the safety of RTE shrimp.