Chitosan films for the microbiological preservation of refrigerated sole and hake fillets

- Chitosan films showed bactericidal effects as an internal layer on fish.
- Fish bacteria was considerably inhibited by the presence of chitosan.
- Greater inhibition of the microbial growth occurred under vacuum packaging.

The effect of chitosan films for shelf-life extension of fresh fillets of hake (Merluccius merluccius) and sole (Solea solea) was evaluated over a 15-day storage at 4 ± 1 °C. Fish fillets wrapped in a chitosan matrix were individually packaged in air (AP) and under vacuum (VP). Microbiological analyses (total aerobic mesophilic bacteria, Pseudomonas, H2S-producing bacteria, lactic acid bacteria, Enterobacteriaceae and Listeria monocytogenes were carried out during the shelf-life. The microbial species were inhibited (p < 0.05) by the presence of chitosan films, especially under VP conditions. A significant (p < 0.05) increase of the lag phase and a reduction of the final microbial population were detected mainly for total aerobic mesophilic bacteria, H2S-producing bacteria and Pseudomonas. The present work demonstrates the biocide effectiveness of chitosan as an internal layer of the packaging material, offering a promising alternative which would enhance the quality of fish during refrigerated storage.