Department of Meat Quality, Danish Meat Research Institute, DK-4000 Roskilde, Denmark.
J Anim Sci. 2010 May;88(5):1830-41. doi: 10.2527/jas.2009-2468. Epub 2010 Jan 29.
The current pork slaughter process is primarily optimized to reduce cooler shrink and the incidence of PSE pork. Elimination of the halothane gene and improved preslaughter handling have decreased the incidence of PSE pork and improved the water-holding capacity of the muscle; however, the chilling process has not been optimized to accommodate these changes. The hypothesis that stepwise chilling could improve tenderness without compromising water-holding capacity was tested in this study. The stepwise chilling treatments were composed of a rapid chilling to 10 or 15 degrees C (in a chilling tunnel) and a 6-h holding period at 10 or 15 degrees C, followed by rapid chilling to 4 degrees C. Both treatments were compared directly with a chilling treatment that simulated conventional tunnel chilling; one carcass half from each pig was allocated to a stepwise chilling treatment, whereas the other carcass half was allocated to the control treatment. A total of 42 pigs were slaughtered on 6 slaughter days. Biopsies were collected for analysis of glycogen degradation and glycogen debranching enzyme activity from slaughter until 72 h postmortem, and samples for color, sarcomere length, drip loss, Warner-Bratzler shear force, and sensory analysis were removed from the carcass 24 h postmortem. Substantial temperature differences were obtained during the holding period between the stepwise and conventionally chilled carcass halves. These had almost, but not completely, disappeared by 22 h postmortem, and although the differences were small, pH was significantly (P < 0.01) less in the stepwise-chilled carcasses compared with the control carcasses. The stepwise chilling treatments led to significantly improved (P < 0.01) tenderness in LM without compromising quality indicators or attributes such as pH, drip loss, or ham processing yield, although color of the stepwise-chilled pork was affected. Neither the tenderness of processed semimembranosus muscle nor the shear force of biceps femoris muscle was affected (P > 0.05) because of the smaller temperature differences in these muscles. The improvements in tenderness could be solely attributed to the increased proteolysis postmortem in the stepwise-chilled carcasses, with the greater temperatures favoring proteolytic enzymes involved in muscle protein degradation. Furthermore, the results for glycogen metabolism successfully revealed that both pro- and macroglycogen contributed to the energy generation in postmortem muscles, with degradation of both forms early postmortem.
目前的猪肉屠宰过程主要是为了减少冷却收缩和 PSE 猪肉的发生率而优化的。氟烷基因的消除和宰前处理的改善降低了 PSE 猪肉的发生率，并提高了肌肉的保水性；然而，冷却过程并没有被优化以适应这些变化。本研究假设逐步冷却可以在不影响保水性的情况下提高嫩度。逐步冷却处理由快速冷却至 10 或 15°C（在冷却隧道中）和在 10 或 15°C 下保持 6 小时组成，然后快速冷却至 4°C。这两种处理都直接与模拟传统隧道冷却的处理进行了比较；每头猪的一半胴体被分配到逐步冷却处理中，而另一半被分配到对照组处理中。共有 42 头猪在 6 个屠宰日进行了屠宰。从屠宰到死后 72 小时采集活检样本，用于分析糖原降解和糖原分支酶活性，从死后 24 小时开始从胴体上取样用于颜色、肌节长度、滴水损失、华纳-布拉茨勒剪切力和感官分析的样本。在保持期内，逐步冷却和常规冷却的胴体之间获得了显著的温差。这些温差在死后 22 小时几乎完全消失，尽管差异很小，但与对照组胴体相比，逐步冷却胴体的 pH 值显著（P < 0.01）较低。与对照组胴体相比，逐步冷却处理显著提高了 LM 的嫩度（P < 0.01），而不会影响质量指标或属性，如 pH 值、滴水损失或火腿加工产量，尽管逐步冷却猪肉的颜色受到影响。由于这些肌肉中的温差较小，加工半膜肌的嫩度和股二头肌的剪切力都不受影响（P > 0.05）。嫩度的提高可以完全归因于逐步冷却胴体死后的蛋白质水解增加，较高的温度有利于参与肌肉蛋白降解的蛋白水解酶。此外，糖原代谢的结果成功地表明，前糖原和大糖原都有助于死后肌肉的能量产生，两种形式的糖原在死后早期降解。
