What causes dark, firm and dry (DFD) pork?

The causes of this condition in pork muscle is linked to chemical and physicalchanges in muscle before, during and after harvest of the animal. Similar to that of PSE pork, the DFD condition is also related to acid production in pork muscle after slaughter, but the nature of the chemical change is different. PSE develops because of an accelerated rate of acid production while muscle temperature is still high. Conversely, DFD results from a lack of acid production in the muscle.Muscles destined for DFD pork have low levels of glycogen that restricts the amount of acid that can be produced, and limits pH fall. While both normal and PSE muscle end up with similar “ultimate” (final) pH values of about 5.5, DFDmuscle usually has an ultimate pH above 6.0. This reduced acidity provides increased water-holding ability in the lean, tightly binding water to muscle proteins, and contributing to a firm texture. Muscle cells swollen with retained water and tightly packed together absorb more light (darker color), and also restrict how deeply oxygen can penetrate into the tissue to “brighten” muscle pigment. A period of extended stress on the pig, caused by factors such as severe weather, long transport or unfavorable holding conditions, can deplete muscle glycogen and cause the DFD condition in pork muscle.