The relationship of sarcoplasmic and myofibrillar protein solubility to colour and water-holding capacity in porcine longissimus muscle

In order to investigate the relationship of sarcoplasmic and myofibrillar p rotein solubility to colour and water-holding capacity (WHC) in pork, 60 lo ins were selected to represent the quality classes: PSE (pale, soft, exudat ive), RSE (reddish-pink, soft, exudative), RFN (reddish-pink, firm, non-exu dative) and DFD (dark, firm, dry). PSE samples exhibited lower (p < 0.05) p rotein solubility (sarcoplasmic, myofibrillar and total) compared to the ot her quality classes. RSE samples exhibited lower (p < 0.05) sarcoplasmic pr otein solubility compared to DFD samples. RSE, RFN and DFD samples had simi lar myofibrillar and total protein solubilities. Sarcoplasmic protein solub ility explained 71% of the variation in lightness with a linear decrease in L* value. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS- PAGE) gels of the sarcoplasmic and myofibrillar samples distinctly showed t he association of some sarcoplasmic proteins with the myofibrillar protein fractions in PSE and RSE samples. The sarcoplasmic proteins which precipita ted were phosphorylase, creatine kinase, triose phosphate isomerase and myo kinase for PSE and phosphorylase for RSE samples. Pork colour is highly cor related with precipitation of sarcoplasmic proteins while WHC is affected b y denaturation of myofibrillar proteins (PSE samples) and lower ultimate pH (PSE and RSE samples). (C) 1999 Elsevier Science Ltd. All rights reserved.