Quality of live packaged mussels during storage as a function of size and oxygen concentration

The commercialization of live mussels is limited by their capacity to resist the adverse conditions associated with their removal from the natural environment. Packaging under modified atmospheres has been proposed as an alternative method for the stabilization of mussels and prolong shelf life. This study investigates how different concentrations of oxygen (20, 75 and 85%) influence the percentage mortality and quality of packaged Mediterranean mussels (Mytilus galloproviciallis) of different sizes (30 and 44 units/kg). In general, mussels packaged with oxygen-rich atmospheres had a higher organoleptic rating and lower percentage mortality. The decrease in pH of both the tissues and intervalval fluid was less pronounced in the larger mussels compared to the smaller mussels. Mussel size and packaging atmosphere also influenced the metabolic survival strategies. The smaller mussels produced more ammonium and volatile fatty acids, which decreased as initial oxygen increased. After 10 days of storage no consumption of glycogen was detected in any of the samples analyzed. The marketable period for the mussels, defined as a 20% mortality threshold, was reached earlier in the packages displaying a greater accumulation of acidic and basic metabolites.