DEFINITION OF THE OPTIMUM FREEZING TIME POSTMORTEM FOR MANUFACTURING PORK MEAT

ABSTRACT

Paired experimental design was adopted to investigate the quality difference between pork meat frozen at different times postmortem. Freezing loss, thawing loss, cooking loss, pressing loss, protein solubility, pH and scanning electron microscopy of the meat were measured. Freezing meat 45 min postmortem significantly reduced total loss, thawing loss, cooking loss and pressing loss when compared with meat frozen at 4 and 24 h postmortem. Freezing meat 4 h postmortem also significantly reduced these traits except for pressing loss when compared with meat frozen at 24 h postmortem. So, freezing meat closer to slaughter resulted in higher water-holding capacity. Sarcoplasmic protein solubility of pork meat was significantly higher in meat frozen at 45 min than meat frozen at 4 and 24 h postmortem, and 4 h than 24 h; while the total protein solubility and myofibrillar protein solubility were lower in meat frozen at 45 min postmortem. Increasing the time postmortem before freezing resulted in larger interspaces between fibers of fresh muscle, and led to more and larger intercellular ice crystals, and so decreased the water-holding capacity of the frozen and thawed meat. No differences were seen in the scanning electron micrographs of thawed meat samples frozen at different times postmortem and thawed under the same conditions.

PRACTICAL APPLICATIONS

Frozen storage is an economically favorable way of meat storage. Most of the research had concentrated on freezing temperature or freezing rates, and many researchers had no requirement on the rigor state of the meat before freezing or held the postmortem time constant. No research reported the effects of freezing meat at different times postmortem on the water-holding capacity and structure of pork. In our experiment, we found that the earlier after slaughter the meat was frozen, the better the water-holding capacity. So for manufacturing pork meat it would be better to freeze it earlier after slaughter to lower the amount of total loss, including thawing loss, freezing loss, cooking loss and pressing loss, and enhance the eating quality and the monetary value and improve the freezing procedure. These provide a valuable datum for meat freezing.