Microbiological and Chemical Changes of Spotted Shrimp (Pandalus platyceros) Stored Under Modified Atmospheres

Abstract

Shrimp (Pandalus platyceros) were packed head-on and head-off in pouches with air or 50 or 100% CO₂ and stored at 0 to 2°C for up to 23 d. Carbon dioxide in modified atmosphere pouches dissolved in the liquid phase and the pH decreased. As storage progressed, the pH increased. Only 100% CO₂ was effective in extending the lag in bacterial growth, but the greatest weight or drip was also obtained with this atmosphere. The bacterial flora changed from mixed gram-negative and gram-positive organisms to a predominantly gram-positive flora. Ammonia was produced throughout storage in all atmospheres, but was delayed longer in head-off than in head-on shrimp. Indole was produced readily in air packs but only at low levels in CO₂ packs.