Post-harvest Metabolism Changes In Live Scallop Patinopecten Yessoensis

Scallop(Patinopecten yessoensis) is one of commercially valuable bivalves in China, mainly aquacultured in Dalian. Scallops are generally sold alive in China. In processing, scallop influenced by the stressors(such as temperature, exposure, anoxia and vibration) fitness of live scallops declines, the properties of flavor and taste weakens. It becomes more important to investigate the changes of biochemical metabolism and discussed the effects of stressors on scallops during depuration.The main research contents and conclusions are as follows:(1)The effects of post-harvest handling on biochemical metabolism of live scallops(Patinopecten yessoensis) during dry dew preservation(dry storage) and circulating seawater preservation(wet storage) were studied. Dry storage is that scallops were stored with ice, storage time is 4 days. Wet storage is that scallops were stored with circulating seawater, including three groups: 5℃,10℃ and 10℃ with mechanical vibration, storage time is 7 days. The effects of different post-harvest handling on the biochemical metabolism of live scallops were observed in the 4 groups. And the effects of 3 stressors(oxygen, mechanical vibration and temperature) on the post-harvest live scallops were discussed. The result shows that the energy metabolism of scallops under dry storage conditions were blocked, the acidic metabolites accumulated, the ATP content, AEC and pH value decreased rapidly, eventually lead to death. The adductor muscle of scallops under wet storage conditions of 5 and 10℃ remained higher ATP content, AEC and p H value. And wet storage condition of 5℃ could maintain higher glycogen content than 10℃. As well as at 10℃ with mechanical vibration will lead to the decrease of ATP content, AEC value and the increase of the consumption of glycogen. Therefore, the biochemical metabolism of live scallops is closely related to the post-harvest handling. Oxygen, temperature and mechanical vibration are important stressors to post-harvest scallops.(2)The effects of temperature and mechanical vibration on metabolism of scallop during wet storage were investigated. ①Temperature: The scallops were depurated in circulating sea-water, the depurating temperature was 5℃, 10℃and 20℃. ②Mechanical vibration: The scallops were divided into 3 groups(vibration 0, vibration 5 and vibration 10). Vibration 0 group dealt with no handling, vibration 5 group was dropped from 50 cm height and repeated 5 times, vibration 10 group was dropped from 50 cm and repeated 10 times. Then depurated the scallops in circulating sea-water. The pH value, Arp, ATP related compounds and Glycogen were determined to analyze the effects of temperature and mechanical vibration on metabolism of scallop during wet storage. The result shows that no death was found during depuration. For different temperature depuration: There was no difference in pH value. The Arp content declined after depurating and it decreased the fastest under the temperature of 20℃, followed by 10℃, 5℃. The ATP deceased and its decreasing tendency is similar to that of the Arp. The effects of depurating temperature on glycogen of scallop were not significant. The content of glycogen in 5℃ was only slightly higher than in 10℃ and 20℃. The scallop could maintain the energy reserve at a higher level when it was depurated at a lower temperature. For different mechanical vibration handling: There was no difference in pH value. The Arp content was stable during depuration. After depurating 12 h the ATP decreased from 5umol to 4umol and became constantly and there was no difference among the 3 groups. The glycogen was stable. Therefore, the mechanical vibration will not affect the physiological status of live scallop significantly(3)The effects of exposure on metabolism of scallop during dry storage were investigated. Scallops were separated into 3 groups and exposed at low temperature(1±0.5℃) for 0h, 12 h and 24 h respectively. And then the scallops were depurated at seawater(2.7 ± 0.2 ℃) for 72 hours. During depuration pH value, Phosphoarginine(Arp), ATP related compounds and Glycogen were determined to analyze the effects of short time exposure on metabolism of scallop. The result shows that after re-watering the pH value was no changes. The Arp content increased gradually, but there was no difference among the 3 groups. The ATP content of exposure 0h group increased, but only slightly higher than the other two groups. The glycogen was slightly decreased, but there was no difference among the 3 groups. Therefore, at low temperature condition short time exposure(<24h) will not affect the physiological status of live scallop significantly.(4) Iced storage scallop adductor muscle quality not only depends on the storage conditions, the handling before processing of live scallop also exist great influence. In order to evaluate the effects of depuration on ice stored scallop adductor muscle, scallops were depurated for 0d, 3d and 7d by 10℃ seawater respectively. Then shucked the scallops and stored the adductor muscle on ice for 7d respectively. During ice storage the rate of rigor, ATP and its related compounds, K value, glycogen, the content and composition of soluble protein and pH value of the scallop adductor muscle were investigated. A primary study on depuration showed that there was a clear difference in the ice storage process of scallops among the three groups. The depurating 3d and 7d groups entered rigor mortis stage at third day, and the samples of non-depuration entered at fourth day. ATP of depurating 3d and 7d group can maintain a high content in 0-2d during ice storage, but it decreased faster in the later stage. Glycogen and soluble protein caused more consumption in depuration. Through appropriate depuration can relieve stress and improving the physiological state of the scallop, but the process will increase the consumption of energy reserve, long time depuration is not conductive to maintaining the storage quality of scallop adductor muscle.