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Pale, Soft, Exudative meat, or PSE meat, describes a carcass quality condition known to occur in pork, beef, and poultry. It is characterized by an abnormal color, consistency, and water holding capacity, making the meat dry and unattractive to consumers. The condition is believed to be caused by abnormal muscle metabolism following slaughter, due to an altered rate of glycolysis and a low pH within the muscle fibers. A mutation point in the ryanodine receptor gene in pork, associated to stress levels prior to slaughter are known to increase the incidence of PSE meat. Although the term "soft" may look positive, it refers to raw meat. When cooked, there is higher cook loss and the final products is hard, not juicy. ==Description== Normally, calcium ions are used by the body to activate muscle cells, composed of myofibril. Ca2+ is transported out of the sarcoplasmic reticulum by ryanodine channels〔 to the cytoplasm of muscle fibers/cells (called sarcoplasm), the process responsible for contractions of the myofibers. Under PSE conditions, twice the amount of Ca2+ can be released post-mortem, which causes excessive glycolysis and the buildup of lactic acid since the metabolism post-mortem is anaerobic. This lactate accumulates in the postmortem muscle, and leads to a very low pH. As the pH drops, proteins in the myofibers are denatured, leading to abnormal cell structure. The result is a pale tissue color, and a soft, almost mushy texture. The sarcomeres collapse excessively, and less water is held within the cell membrane and proteins. Subsequently, the myofibers will continue to lose water content as the meat is cooled and stored, leading to excessive drip loss.〔 Pigs susceptible to porcine stress syndrome, or PSS, have an increased likelihood of developing PSE meat. These animals become easily stressed pre-slaughter, which leads to exaggerated glycolysis, an increase in body temperature, and higher production of lactic acid. In particular, the Halothane gene, ''Hal'', induces PSS in swine. It is a single point mutation in this gene that causes abnormal calcium channels within the muscle. ''Hal+'' pigs are five times more likely to develop PSE meat than ''Hal-'' hogs.〔 The incidence of PSE in poultry meat is believed to have increased over the past several decades because of the incredible advancements in growth rates. Intense breeding selection for breast size and feed efficiency is likely responsible for the increase in meat quality issues. Conditions behind the PSE poultry meat are believed to be the same as observed in pork; higher rates of glycolysis postmortem lead to a sudden pH drop, which in turn causes protein denaturation and a loss of functionality,〔 important factor to create meaty products, such as sausages. Although the same ryanodine mutation found in pork was not found in poultry, differences in α-ryanodine and β-ryanodine were found. Avian species have lower quantities of the β isoform. This isoform of the channel is more reactive to Ca2+ accumulation, and once activated, remains opened for a longer period in which it is irresponsive, therefore, relatively higher number of α-channels pumps higher calcium ions to the sarcoplasm at a higher speed, contributing to pH lowering. For this similarity, PSE in other species than pork can be referred to as "PSE-like". 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「PSE meat」の詳細全文を読む スポンサード リンク
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