Effect of modified atmosphere packaging on oxidative changes in frozen stored cold water shrimp (Pandalus borealis)

Shrimps caught at sea were boiled in seawater, air blast or nitrogen frozen, glazed and then packed in plastic bags with a low oxygen transmission rate. The bags were either flushed with nitrogen (modified atmosphere packaging) or with atmospheric air before sealing. The shrimps were then stored for up to 12 months in a freezer cabinet at −17°C with fluctuating temperatures. During storage they were either exposed to fluorescent light or kept in darkness. To investigate the effect of fluctuating temperatures some of the modified atmosphere-packed shrimps were stored in darkness in a cold store at a constant temperature of −18°C. Quality changes were determined by sensory evaluation combined with chemical/physical analyses, including determination of the pigment astaxanthin and measurement of the oxidative stability by determination of thiobarbituric acid-reactive substances (TBARS). Packaging in modified atmosphere resulted in overall better quality in relation to colour fading, development of rancid flavour and toughening of the meat. Light exposure influenced both colour fading and lipid oxidation negatively. Temperature fluctuations resulted in very pronounced formation of frost in the packages. After 6 to 9 months of frozen storage, the amount of frost corresponded to the weight of the glazing layer applied before storage.