Abstract:

The changes in some chemical parameters related to color stability of different quality groups of pork during refrigerated storage were measured. Three quality groups of PSE (pale, soft, exudative), RFN (red, firm, not exudative) and DFD (dark, firm, dry) chilled pork were sampled at 24 h post mortem or after ageing for 4 days post mortem, packaged in polyethylene foam trays (oxygen transmission rate, 5000 ml /(m2 ·24 h)) and stored in dark environment at( 2 ± 1)℃ for 6 days. Metmyoglobin (MetMb) reductase activity, thiobarbituric acid reactive substances (TBARS) and pH were measured at intervals of 24 h; and some enzymological characteristics of MetMb reductase were also examined. MetMb reductase activity and TBARS were significantly affected by pork quality groups (PSE, RFN and DFD), ageing and storage time. The MetMb reductase activity of DFD chilled pork was significantly higher than those of PSE and RFN chilled pork during refrigerated storage. Ageing and refrigerated storage both reduced the MetMb reductase activities of RFN and PSE chilled pork and increased the TBARS. The optimum temperature and pH for MetMb reductase from pork were 30 ℃ and 6.4, respectively. At 30 ℃, the decrease in pH could reduce the activity of the enzyme; at 2 ℃, however, MetMb reductase activity was decreasing only when pH ＜ 5.7. Therefore, increasing the final pH of pork could adjust its MetMb reductase activity and reduce lipid oxidative substances, which is critical to extending color display shelf life of pork.

Key words: pale soft exudative (PSE) pork , red firm not exudative (RFN) pork, dark firm dry (DFD) pork, metmyoglobin reductase activity, thiobarbituric reactive substances (TBARS), ageing