Freezing Technology

7.3.2 Modified atmospheric packaging and storage

• In 1932, conye reported the beneficial effects of CO₂ in inhibiting the growth of bacteria from fish.
• They have also been applied to other storage systems, namely CO₂ saturated sea water and CO₂ enriched atmospheres.
• Increased storage life of fresh fish and shell fish using refrigerated sea water saturated with CO₂ become evident.
• The results appear to apply to a wide variety of species including fatty species of salmon, low fat rock fish and shrimp.
• When the air surrounding the fish is changed in composition usually by enriching it with CO₂ and the container then sealed the atmosphere is called “modified”.
• Fish and shell fish from modified atmosphere storage have lower bacterial counts, greater acidity level, reduced trimethylamine formation and lower NH₃ production.
• There is also residual and positive effect on the keeping quality after removal from the CO₂ enriched environment.
• Temperature abuse results in bacterial spoilage and possible development of toxins. The accumulation of unpleascent odour in the package owing to the activity of anaerobic organisms.
• The more serious problem is the threat of C. botulinum activity
• The odour are not the usual type of “fishy” odours produced by sea food because of the circulation of fresh gas removes them.