Effect of oxygen concentration and temperature on the viability of small-sized mussels in hermetic packages

The objective of this study was to evaluate the behaviour of small-sized (∼19 g/unit) Mediterranean mussels packaged hermetically with different proportions of oxygen in the interior of the package and stored at 2 °C and 7 °C. The most favourable conservation conditions (83% O2 and 2 °C) were compared with larger mussels (∼24 g/unit). On day 3 of storage with 20 %O2 at 2 °C, the concentration of volatile fatty acids in the intervalval fluid was double that for the mussels packaged with 83% O2 and this difference increased during storage. Higher temperatures produced a larger and more rapid accumulation of ammonium nitrogen with concentrations of 49 mg N/L on day 6. Lower concentrations were observed at the end of storage at 2 °C (27 mg N/L on day 9). From day 7, the increase of N-TVB measured in the intervalval fluid of the small mussels at 2 °C was more pronounced than in the larger mussels. The organoleptic evaluation, percentage mortality and microbial counts collectively indicated that a high quality product was maintained on day 8-9 at 2 °C with mussels packaged with 83% O2. Inadequate temperatures have a stronger negative impact on shelf life than low oxygen concentrations.