Technical Abstract: This study evaluated the effects of hydrodynamic pressure processing (HDP) and aging on the sarcoplasmic proteins of beef strip loins. Loins (n=12) were halved at 48 h postmortem and assigned to HDP or control treatments. Following treatment, each half was divided into three portions for aging (0, 5, or 8 days). Samples were removed for Warner-Bratzler shear force (WBSF) determination and sarcoplasmic protein isolation. SDS-PAGE analysis found that HDP influenced protein bands corresponding to 143, 65, 44, 36, and 19 kDa. Aging influenced the band intensity of 22 sarcoplasmic proteins. Changes in sarcoplasmic protein composition were significantly correlated to WBSF (r= -0.58 to 0.45). Sarcoplasmic protein solubility decreased with both HDP (P<0.05) and aging (P<0.0001). Changes in solubility were significantly correlated to SDS-PAGE band intensities (r= -0.53 to 0.60). Data suggest that HDP and aging cause changes to sarcoplasmic proteins that may be indicators of proteolysis and tenderization.