Technical Abstract: Capillary electrophoresis (CE) and reversed-phase high performance liquid chromatography (RP-HPLC) analysis were utilized to detect differences in the sarcoplasmic protein profiles of beef strip loins subjected to aging and hydrodynamic pressure processing (HDP) treatments. At 48 h postmortem, strip loins (n=12) were halved and subjected to control or HDP treatments. Following treatment, each half was divided into three portions which were aged for 0, 5, and 8 days. After each aging period, steaks were removed for Warner-Bratzler shear force (WBSF) analysis and for the isolation of sarcoplasmic protein fractions which were analyzed by CE and RP-HPLC. Aging by HDP interactions were not detected within the sarcoplasmic protein fractions using either separation technique. With CE analysis, no significant HDP effects were observed; however, the relative peak area of eight protein peaks ranging in size from 17 to >200 kDa were influenced by postmortem aging. RP-HPLC separation of sarcoplasmic fractions demonstrated that HDP influenced the relative size of two protein peaks while postmortem aging effects were observed in six peaks. Alterations in the sarcoplasmic protein fraction detected by both CE and RP-HPLC were significantly correlated to WBSF measurements. Overall, data demonstrate that aging and HDP have additive effects on sarcoplasmic proteins and suggest that changes in sarcoplasmic protein profiles may be useful indicators of tenderness.