Sarcoplasmic proteins influence water-holding capacity of pork myofibrils

Water-holding capacity (WHC) is one of the main pork quality characteristic s. The objective of this study was to determine the influence of (denaturat ion of) sarcoplasmic proteins on WHC. Myofibrils extracted from red, firm, non-exudative ('normal') and PSE (pale, soft, exudative) pork longissimus m uscle were combined with sarcoplasmic extracts (with or without proteins) f rom PSE and normal pork longissimus samples. Weight increase of myofibrils (mg increase mg(-1) myofibrillar protein) was used as a measure of WHC. Whe n combined with protein-containing sarcoplasmic extract from normal pork, W HC of myofibrils from PSE (2.6 mg mg(-1)) and normal (2.8 mg mg(-1)) pork w as higher (P < 0.05) than when combined with sarcoplasmic extract from PSE meat (1.3 mg mg(-1) for PSE and 1.9 mg mg(-1) for normal myofibrils). Prote in-free sarcoplasmic extracts were prepared by heating the extracts for 30 min at 80 degrees C. WHC of myofibrils combined with protein-free sarcoplas mic extract from PSE and normal pork was not significantly different. WHC o f myofibrils combined with protein-free extract was lower than WHC of myofi brils combined with protein-containing extract. Ionic strength or pH could not explain the observed differences. It was concluded that sarcoplasmic pr oteins do influence WHC. The mechanism of this influence still needs to be determined. (C) 1999 Society of Chemical Industry.