The scientists study was to evaluate the effect the use of natural additives, superchilling, and modified atmosphere packaging (MAP) would have on shelf life of salmon, as they note that there has not been previous research focused on such a preservation method. The authors explained that there are inferences on the use of MAP on fish preservation; although unification of criteria is difficult due to differences in fish species, gas mixtures and storage temperatures.
It is said that Norway and Chile are the main producers of Atlantic salmon, and export to countries such as the US, Japan and Germany. The study revealed that the shelf life of fresh fish is normally between seven to eleven days using traditional packaging, and the burden lies with the producer to ensure original product quality right to the final destination. MAP works by replacing the normal atmosphere in the pack by a specified gas mix, the main components of which are oxygen, carbon dioxide and nitrogen.
The authors said they undertook three different sets of experiments: the first focused on evaluating the effect of including natural additives together with superchilling and MAP. A control (exposed to air) sample was included in the three sets of experiments. The superchilling process involved placing the fish into the centre of a freezing tunnel cooled by air convection, and keeping them in the tunnel for 30 minutes, in order to reach -1.5 °C in the centre of fillets.
The results showed that the combined effect of the three technologies of natural additives, MAP and superchilling did not improve the salmon shelf life, and also impacted negatively on appearance and odour of the salmon. However, the authors found that the use of the combination of superchilling and MAP incorporating a CO2 concentration of 90 percent and a g/p ratio of 2.5 resulted in the longest shelf-life of 22 days as compared to 11 days in a control sample.
