Mortensen Margit, Andersen Henrik Jørgen, Engelsen Søren Balling, Bertram Hanne Christine
Danish Institute of Agricultural Sciences, Department of Food Science, Research Centre Foulum, P.O. Box 50, DK-8830 Tjele, Denmark.
Meat Sci. 2006 Jan;72(1):34-42. doi: 10.1016/j.meatsci.2005.05.027. Epub 2005 Jul 27.
The effects of freezing temperature (-20 versus -80°C) in combination with long-term freezer storage (-20°C) on water mobility and distribution in pork of two qualities (normal and high ultimate pH) were explored using low-field NMR T(2) relaxometry. A marked effect of freezing temperature on the characteristics of intra- and extramyofibrillar water (T(2) relaxation times) in the thawed pork was demonstrated, implying that the freezing temperature in combination with prolonged freezer storage affects the distribution and chemical-physical state of water in the thawed meat. Determination of technological properties (thawing and cooking loss) revealed that the observed T(2) variations related to water distribution and water properties, which were found to be consistent with the degree of structural damage assessed by light microscopy, also were reflected in the technological quality of the meat. Low freezing temperature in combination with prolonged freezer storage was associated with increased thawing and cooking loss. In addition, pH in the fresh meat had a pronounced effect on the distribution of myofibrillar water, as a more homogenous pore size distribution was evident in meat with high pH compared with normal pH. A clear effect of cooking rate on the T(2) relaxation characteristics in the cooked pork was also demonstrated, probably reflecting a cooking rate-induced effect on the myofibrillar structures. The effect of cooking rate on water distribution resulted in a significantly lower cooking loss upon a slow cooking rate (0.5°C/min from 25 to 65°C and 0.3°C/min from 65 to 80°C) compared with a fast cooking rate (1°C/min).
采用低场核磁共振 T(2) 弛豫分析法，探究了两种品质（正常和高最终 pH 值）猪肉在冷冻温度（-20 与 -80°C）以及长期冷冻储存（-20°C）条件下对水分流动性和分布的影响。结果表明，冷冻温度对解冻猪肉中肌原纤维内和肌原纤维外水分的特性（T(2) 弛豫时间）有显著影响，这意味着冷冻温度与延长的冷冻储存时间相结合会影响解冻肉中水分的分布和化学物理状态。技术特性（解冻和烹饪损失）的测定表明，观察到的与水分分布和水分特性相关的 T(2) 变化与通过光学显微镜评估的结构损伤程度一致，也反映在肉的技术品质上。低冷冻温度与延长的冷冻储存时间相结合会导致解冻和烹饪损失增加。此外，鲜肉的 pH 值对肌原纤维水分的分布有显著影响，与正常 pH 值的肉相比，高 pH 值的肉中孔径分布更均匀。还证明了烹饪速率对熟猪肉中 T(2) 弛豫特性有明显影响，这可能反映了烹饪速率对肌原纤维结构的影响。与快速烹饪速率（1°C/分钟）相比，慢速烹饪速率（从 25 至 65°C 为 0.5°C/分钟，从 65 至 80°C 为 0.3°C/分钟）下烹饪速率对水分分布的影响导致烹饪损失显著降低。
