Effect of a finishing period in sea on the shelf life of Pacific oysters (C. gigas) farmed in lagoon

The aim of this paper was to compare the influence of a five-month finishing period in a sea or in the lagoon site on quality changes during chilled storage of Pacific cupped oysters (C. gigas), farmed in the lagoon. The oysters were analysed for morphological and chemical characteristics, and for parameters useful to monitor changes during shelf life (intervalvar liquid content, colour, volatile organic compound profile, pH and microbiological load) on 1st, 3rd, 7th and 10th days of refrigerated storage at 4 °C. Oysters finished in the lagoon showed a higher incidence of soft part and higher condition indexes, even though oysters finished in the sea had larger biometric dimensions. Lagoon-finished oysters had edible part richer in total lipids (11.82 vs 9.34%) with lower percentages of PUFAn-6 and C20:5n-3, whereas C22:6n-3 percentages were similar. From sensory analysis, sea-finished oysters were judged saltier and more bitter, whereas lagoon-finished oysters kept better during refrigerated storage, presenting more stable pH values, higher retention of intervalvar liquor and a moderate capacity to control bacterial proliferation during 10 days of refrigerated storage. The profile of volatiles was the same in both groups of oysters, but the amounts of each volatile tended to be significantly higher in lagoon-finished oysters. The finishing period in the sea induced a decrease in quality of all market and sensory characteristics and poorer storage performance. The better nutritional status of lagoon-finished oysters at harvest, the better trophic conditions of lagoon finishing and the better adaptation of the molluscs to a wide range of fluctuations in environmental parameters were presumably linked to their greater ability to withstand hypoxia during out-of-water refrigerated storage.