Effect of modified atmosphere packaging on shelf-life of iced fresh hake slices

Shelf-life of hake slices (Merluccius merluccius) stored in the ice state (2 +/- 1 degrees C) under modified atmosphere packaging (MAP) conditions was determined by measurements of pH, total volatile bases (TVB) and trimethylamine (TMA) content, mesophilic and psychrophilic bacterial counts, malonaldehyde content, exudation, protein functionality and sensorial analyses (colour and odour). The effect of different gas mixtures were evaluated: (1) 40% CO2, 50% N-2, 10% O-2;(2) 60% CO2, 30% N-2, 10% O-2; (3) 40% CO2, 30% N-2, 30% O-2;(4) 60% CO2, 10% N-2, 30% O-2 and (5) air (control). Important differences were found between MAP-stored and air-stored bake slices. Shelf-life of hake stored under MAP conditions was two-fold extended. Bacterial growth was inhibited, increases of pH, TMA and TVB were reduced, and alterations in protein functionality were delayed, and off-odours were not noted in MAP-stored hake slices after 21 days storage. Significant correlations were found between TMA content and total viable count (TVC), as well as between apparent viscosity and exudation. Hake slices could be stored in the ice state under MAP conditions for about three weeks without an important loss of quality. Fish freshness, handling practices and initial bacterial load have an important influence of shelf-life of hake.