Characterisation of PSE zones in semimembranosus pig muscle

Pig semimembranosus muscles, sampled from normal hams or from PSE-zones of defective hams, were analysed by histochemistry and electrophoretic techniques. PSE zones were characterised by a disorganisation of fibre alignment and a significant increase of inter fibre spacing (26.2% vs. 16.9%, p < 0.05). Protein solubility was significantly lower in defective muscle (55.4 vs. 91.5 mg/g, p < 0.001). SDS-PAGE evidenced in such samples a lower abundance of the 97, 40 and 26 kDa bands in the sarcoplasmic fraction and a higher abundance of the 97, 58, 34, 31, 15 and 11 kDa bands in the myofibrillar fraction. Intensity of the MHC band (200 kDa) was lower in PSE zone samples. By 2-D electrophoresis, it was shown that troponin T, MLC 1 and alpha-crystallin were less proteolysed in defective muscles, while creatine kinase fragments were more represented. One form of HSP 27 was absent from PSE zone samples. Overall, meat from PSE-zones and fast pH fall-PSE meat show numerous histological and biochemical similarities, particularly in their protein characteristics.