Agar films containing green tea extract and probiotic bacteria for extending fish shelf-life

- Bioactive film composed of agar, green tea extract and probiotics was applied on hake.
- Bioactive film reduced the microbial growth, specially the H2S-producing bacteria.
- Probiotic strains passed to muscle increasing beneficial lactic acid bacteria in fish.
- Bioactive films caused a decrease in the biochemical indexes of fish.
- Bioactive films with green tea and probiotics extended the shelf-life of hake.

A bioactive film composed of agar, incorporating green tea extract and probiotic strains (Lactobacillus paracasei L26 and Bifidobacterium lactis B94) was applied on hake fillets in order to evaluate the effect of the films during 15 days of storage. Hake was previously inoculated with Shewanella putrefaciens and Photobacterium phosphoreum (103-104 CFU/g) to simulate a spoilage process. The green tea and/or probiotic film provoked a reduction, particularly of H2S-producing bacteria counts and total viable bacteria throughout the storage period. The probiotic strains added to the film could pass to the fish producing an increment of lactic acid bacterial counts, even in the presence of green tea extract. The effect of the films also caused a decrease in the indexes of fish quality (total volatile basic nitrogen (TVB-N), trimethylamine nitrogen (TMA-N) and pH). The total viable counts, H2S-producing microorganisms and TVB-N were maintained below the limits of acceptability during 15 days for the fillet covered with the green tea + probiotic film, compared to the rest of the samples. Films with green tea and probiotic were able to extend shelf-life of hake at least for a week and increase the beneficial lactic acid bacteria in fish.