Oyster is one of the most popular shellfish in the world and the Pacific oyster (Crassostra gigas) is the main species of oyster consumed. With the popularity of oyster bars in recent years, demand for live oysters is on the rise. However, during the harvesting and transportation, the energy of oyster will be affected due to the forcing stress and oysters with low initial energy could also affect the shelf life. Therefore, there is an essential need to recover the energy of oyster before preservation. Rearing is one of the common methods to recover the vitality of fish or shellfish. According to the results of our previous experiments, shelled Pacific oysters were still alive and could be accepted for raw consumption at 3 weeks during the superchilling storage at -1? and shelled oysters could have a longer shelf life when they are alive. Therefore, oysters with higher initial vitality could have a longer shelf life or not is unclear. Our study was to investigate the effects of rearing on quality and freshness of pacific oyster during storage.
Live cultured Pacific oysters (n = 40) was divided into two groups: rearing 1 day (A) and rearing 3 days (B). Oysters were rearing by deep ocean water before storage. All the groups were storage at -1? for 10 days. The determination of pH value, ATP-related compounds was taken to indicate the changes in freshness. The AEC value has been used as a parameter that can reflect the quality of aquatic products.
AEC value (%) = 1/2 (2 ATP + ADP) / (ATP+ADP+AMP) ×10
After rearing, the group of rearing 3 days had a higher level of ATP than group of rearing 1 day. Only ATP, ADP and AMP could be detected, because all the oysters were alive. The AEC values of group A decreased from 53% (day0) to 24.35% (day 7). However, in group B, the initial AEC value is 59.78%. In contrast to group A, the AEC value only reduced to 45.52% after 10 days. The pH value of group A dropped from 6.78 to 6.49. In group B, the pH value was kept around 6.7 during the storage. The results indicated that rearing has positive effect on the quality and freshness of pacific oyster.