武昌鱼宰后4 ℃冷藏条件下品质变化规律

通过对武昌鱼宰后4 ℃冷藏条件下72 h内僵直指数、质构、pH值、持水力、白度、5’-三磷酸腺苷（5’-adenosine triphosphate，ATP）及其关联物含量的测定和分析，探究武昌鱼的品质变化规律。结果表明：武昌鱼宰后6 h的硬度、僵直指数明显高于其他时间点，之后开始下降；武昌鱼宰后pH值迅速下降，宰后6 h时降低至6.58±0.04，随后逐渐上升；武昌鱼的持水力先下降再升高；白度在宰后72 h时降低至38.02±0.23；宰后2 h时ATP含量最高，5’-一磷酸腺苷（5’-adenosine monophosphate，AMP）含量与ATP变化趋势相似，AMP在AMP脱氨酶的作用下降解产生5’-肌苷酸（5’-inosine monophosphate，IMP），宰后0～4 h内IMP含量上升，IMP经磷酸酶转化为肌苷和次黄嘌呤（hypoxanthine，Hx），从宰后36 h起Hx含量增加速率明显增大；宰后24 h内，K值保持在20%以内的一级鲜度范围，宰后24～72 h仍然保持在20%～40%的二级鲜度范围。

Quality Changes of Megalobrama amblycephalala during Postmortem Storage at 4 ℃

The quality changes of Megalobrama amblycephalala were evaluated in terms of stiffness index, texture, pH, water-holding capacity, whiteness, and the contents of 5’-adenosine triphosphate (ATP) and related compounds during 72 h of postmortem storage at 4 ℃. At 6 h after slaughter, the hardness and stiffness index reached their peak, and then fell. The pH decreased rapidly after slaughter, decreasing to 6.58 ± 0.04 at 6 h, and then rose gradually. The water-holding capacity decreased firstly and then increased. The whiteness first rose and then fell to 38.02 ± 0.23 at 72 h. The ATP content was the highest at 2 h, and its trend was similar to that of 5’-adenosine monophosphate (AMP). The content of 5’-inosine monophosphate (IMP), produced from AMP degradation catalyzed by AMP deaminase, increased from 0 to 4 h. The content of hypoxanthine (Hx) increased significantly faster from 36 h onward. The K value was kept below 20% (the first freshness grade) up to 24 h after slaughter and remained within the range of 20%–40% (the second freshness grade) from 24 to 72 h.