Examination of the potential of refrigerated seawater to improve live transport of the mussel Perna canaliculus: Physiological responses, meat quality and safety implications under different chilled storage conditions

Refrigerated seawater (RSW) based systems for post-harvest storage of green-lipped mussels (Perna canaliculus; also known as GreenshellTM mussels) were assessed. Two post-harvest storage trials were conducted in October 2020 and March 2021 (austral spring and summer respectively) on mussels recovered for 2.5 days after harvest in flow-through seawater. The mussels were randomly assigned to three post-harvest treatments, all conducted at 6.5 degrees C for 10 days: Chilled in air; immersion in recirculated RSW; and Periodic immersion in RSW (6 min h-1). A range of physiological, morphometric and quality measures were screened to assess their ability to indicate mussel performance. Further to this, mussels in duplicate systems were inoculated with Escherichia coli and Vibrio parahaemolyticus to inform on risks associated with pathogen proliferation. The mussels interacted with the seawater in both the RSW and Periodic RSW systems as seawater ammonia concentrations increased in both. Mussel mortalities counted across the 10-day trials were highest in the Chilled treatment (5.5%), followed by RSW (3.5%) and Periodic RSW (2.4%). Key measurements including haemolymph pH and osmolality, meat and intra-valvular water weight, and textural hardness, were all affected by the post-harvest treatments. For inoculated mussels, E. coli and V. parahaemolyticus most probable numbers (MPN) remained stable in both the Chilled and Periodic RSW treatments with reductions in both bacteria recorded in the RSW treatment. Higher variances in intra-valvular water retention and haemolymph haemocyte numbers and differences in volatile organic compound profiles were seen in the summer mussels, as compared with spring, highlighting mussel condition as a determining factor for post-harvest performance. RSW has therefore been demonstrated to be beneficial, but optimisation (e.g., through further reduction of metabolic activity) may further increase practical post-harvest transport distances and the quality of live/fresh mussel products.