Prediction of optimal CO₂ emitter capacity developed for modified atmosphere packaging of fresh salmon fillets (Salmo salar L.)

Pieces of pre‐rigor filleted Atlantic salmon were modified atmosphere (MA)‐packaged (60% CO 2 and 40% N 2 ) in eight different ways according to tray sizes (ml), gas/product ratios (g/p ratios), number of fillet layers and capacities of the CO 2 emitters being used (based on the fish weight or on the surface area of the fish). All the samples were stored at 2°C for 21 days. Gas measurement showed that the CO 2 emitter based on fish weight developed too much CO 2 , and the emitters based on surface area developed too less during storage. Samples with the lowest CO 2 level in the headspace (emitter based on surface area), and also probably the lowest amount of absorbed CO 2 , had the highest bacterial growth after 17 days of storage for some of the samples. Both the pH and the bacterial growth were similar between the top layer and the bottom layer within the packages of more than one layer in each tray. This indicates that the CO 2 was also available for the bottom layers. The liquid loss was similar for the trays with the different emitter types, but it differed between the tray sizes. A model based on the weight and surface area of the fish, and g/p ratio and capacity (ml) of the tray was made in order to more precisely calculate an optimal amount of the CO 2 emitter ingredients because of a predefined CO 2 level in the headspace.