The Exploration Of Sinonovacula Constricta And Meretrix Meretrix In ATP Degradation Pathways And Its Quality Changes During Chilled Storage

Sinonovacula constricta and Meretrix meretrix are a kind of marine shellfish that have higher edible and economic value.Their processing modes are based on fresh selling, forrowed by processing into dry goods and frozen goods. To some extent, the further developments of shellfish aquaculture are restricted by composition and current production, processing and transport limitations of shellfish meat. So, for S. constricta and M. meretrix, an important issue it faces is preservation processing. Early scholars hold the opinion that the adenosine triphosphate (ATP) degradation pathways in marine invertebrates are different with fish. The ATP degradation pathway in Shellfish has been controversial and It remains to be explored whether K value (fish freshness evaluation index) can be applied to the evaluation of freshness in S. constricta and M. meretrix.In view of this, it studied on ATP degradation pathways and the changes of quality in a low temperature of S. constricta and M. meretrix in this paper. Firstly, Methods was optimized on determination of all the possible substances which were related to the ATP degradation in several pathways in shellfish, including related products and possible substances to disturb this process. Secondly, the kinds and contents of ATP-related compounds of S. constricta and M. meretrix were analyzed according the above optimizing HPLC-DAD methods. After then, the pathways of ATP degradation in S. constricta and M. meretrix were preliminarily determined. Thirdly, Sensory assessment and TVB-N value were used to evaluate two shellfish freshness, establishing a new freshness index Kax which are closely correlated with the changes of ATP related compounds. Fourthly, the Vigor state, sensory evaluation, ATP related compounds, free amino acids, pH value, TVB-N value were used to evaluate Vigor and the quality changes in S. constricta and M. meretrix throughout the storage. The main research results are as follows:1. An HPLC-DAD method for the analysis of 10 nucleotides and related compounds (NRCs) in shellfish meat was optimized. The 10 nucleotides related compounds are:ATP, GMP, ADP, AMP, IMP, AdR, HxR, Hx, Ad and Xt. The optimizing experimental conditions were as follows. Samples were separated on an ODS-3 C18 (4.6 mm × 250 mm,5 μm) column with 0.015 M phosphate buffer (pH=5.7) as mobile phase A. The UV detection was performed at 254 nm. All 10 NRCs were completely separated within 30 min. Good linearity was seen in the concentration range from 1～750 μg/mL with correlation coefficients between 0.9998～0.9999. Limit of detection was between 0.02～0.053 μg/mL and spike recoveries were between 86.8%～ 107.2%.This method is facile, reliable, and accurate for the analysis of 10 NRCs in S. constricta and M. meretrix samples.2. A similar changes of the ATP-related compounds showed in S. constricta and M. meretrix during chilled storage at 4±1 ℃. ATP and ADP were declining, AMP, IMP, AdR, HxR all offered first increased and then decreased. Xt were rising. Hx in S. constricta were rising but in M. meretrix offered first increased and then decreased. Ad were not detected in two shellfish. M. meretrix had few content of AdR. According to changes in ATP-related compounds, it was speculated the degradation pathways of two shellfish might be:ATPâ†'ADPâ†'AMPâ†'IMPâ†'HxRâ†'Hxâ†'Xt,ATPâ†'ADPâ†' AMPâ†'AdRâ†'HxRâ†'Hxâ†'Xt. Combined with sensory evaluation and TVB-N,it was highly significant correlation in sensory scores,TVB-N values and the Kax-value of two shellfish.Kax-value could be used to review the fresh degree of two species of shellfish.3. Developed an Vigor state table, the storage of fishery products is divided into four parts, Fresh period, half-dead period, of dying and death in 4±1 ℃.In 10d and 11d, the mortality rates are more than 50% of A and B,respectively. Among them, fresh period to half-dead period on stage, ATP, ADP were declining gradually, AMP offered first increased and then decreased.The total content of ATP related compounds is essentially the same. Calculation of V-value as follows.V-value can be used to evaluate the changes of the Vigor and quality of S. constricta and M. meretrix living in 4±1 ℃.It can be the Ala that a potential indicator for the Vigor and quality assessment of S. constricta during its entire storage. Tau is a potential indicator that only suitable as an evaluation of fresh till half dead of Vigor and change the quality of M. meretrix. For S. constricta and M. meretrix, pH value is not a representative index, TVB-N value can only detected the changes of corruption.