Straadt Ida Krestine, Rasmussen Marianne, Andersen Henrik Jørgen, Bertram Hanne Christine
Department of Food Science, Danish Institute of Agricultural Sciences, Research Center Foulum, P.O. Box 50, DK-8830 Tjele, Denmark.
Meat Sci. 2007 Apr;75(4):687-95. doi: 10.1016/j.meatsci.2006.09.019. Epub 2006 Nov 17.
Confocal laser scanning microscopy (CLSM) and low-field nuclear magnetic resonance (LF-NMR) relaxometry were combined to characterize microstructural changes and water distribution in fresh and cooked pork during an aging period of 14 days. At day 1 (24h postmortem) a few muscle fibres, which appear swollen, were observed in both fresh and cooked meat. An identical microstructure was still apparent after 14 days, however, the number of muscle fibres showing distinguished characteristics was found to increase throughout the aging period. Hence, it was apparent that during aging the individual fibres swell and disintegrate at different rates. Development in water-holding capacity (WHC) was followed during the aging period using gravimetric methods, and an increase in the WHC in the fresh meat was observed, which resembled the amount of extramyofibrillar water measured by NMR relaxometry (T(22) population). This was consistent with the CLSM images, as a substantial increase in the number of myofibrils that appeared swollen, capable of holding more water, was observed during aging. In the cooked meat the width of the T(21c) population, reflecting the myofibrillar water in the cooked meat, was seen to decrease during the entire storage period, which corresponds to the development of a more homogeneous structure. In the CLSM data a continuous degradation during the storage period was observed, which could resemble a shift to a more homogeneous structure. Comparison of CLSM of transverse sections of fresh and cooked pork revealed a pronounced shrinkage of muscle fibres upon cooking. This resulted in large gaps between the cooked muscle fibres, which also was visible as shrinkage at the level of the individual myofibrils. This pattern was also reflected in the NMR relaxation data. The cooking-induced shrinkage of the myofibrils occurred concomitantly with a decrease in the amount of intermyofibrillar water within the individual fibre and an increase in the larger extramyofibrillar spaces between fibres, i.e. water is expelled from the myofibrillar matrix upon cooking. Accordingly, the present study demonstrated that the use of CLSM together with NMR relaxometry can provide further information on the relationship between structural characteristics of meat and resultant water distribution.
共聚焦激光扫描显微镜（CLSM）和低场核磁共振（LF-NMR）弛豫测量法相结合，用于表征新鲜猪肉和熟猪肉在14天成熟期间的微观结构变化和水分分布。在第1天（宰后24小时），在新鲜肉和熟肉中均观察到一些出现肿胀的肌纤维。14天后，相同的微观结构仍然明显，然而，发现显示出明显特征的肌纤维数量在整个成熟期间有所增加。因此，很明显在成熟过程中，各个纤维以不同的速率膨胀和分解。在成熟期间使用重量法跟踪持水能力（WHC）的变化，观察到新鲜肉中的WHC增加，这与通过NMR弛豫测量法（T(22)群体）测量的肌原纤维外水分量相似。这与CLSM图像一致，因为在成熟过程中观察到出现肿胀、能够容纳更多水分的肌原纤维数量大幅增加。在熟肉中，反映熟肉中肌原纤维水分的T(21c)群体宽度在整个储存期间都有所下降，这对应于更均匀结构的形成。在CLSM数据中，观察到储存期间的持续降解，这可能类似于向更均匀结构的转变。新鲜猪肉和熟猪肉横切面的CLSM比较显示，烹饪后肌纤维明显收缩。这导致熟肌纤维之间出现大的间隙，这在单个肌原纤维水平上也表现为收缩。这种模式也反映在NMR弛豫数据中。烹饪引起的肌原纤维收缩伴随着单个纤维内肌原纤维间水分量的减少以及纤维间较大的肌原纤维外空间的增加，即烹饪时水分从肌原纤维基质中排出。因此，本研究表明，CLSM与NMR弛豫测量法一起使用可以提供关于肉的结构特征与所得水分分布之间关系的更多信息。
