The amount and composition of the proteins in drip from stored pig meat

In order to elucidate the mechanism of drip formation, measurements have been made of the amount of drip, and its protein concentration, from 80 pigs chilled conventionally. The correlation between amount of drip and protein concentration was poor but significant (r = -0·41, P < 0·001). The individual protein components of 20 drip samples were analysed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Relative protein composition varied with amount of drip. As the amount of drip increased above about 12% the absolute amounts of some proteins decreased; these proteins were creatine kinase and/or phosphoglycerate kinase (under the system used, these two proteins comigrate and therefore cannot be distinguished), myokinase, and an unidentified protein of molecular weight 137000. Drip contained similar proteins to a sarcoplasmic extract and in similar amounts. These results show that drip is mainly sarcoplasmic in origin and we suggest that the systematic changes in individual proteins as the amount of drip increases may be explained by denaturation of some or all of these proteins and possibly by dilution with fluid from within the myofibril.