Fresh Pork Loin pH Influences Meat Quality and the Presence of Desmin Degradation Products

This study aimed to test the hypothesis that pork loin pH at 1-day postmortem influences fresh pork quality and degradation of desmin. Fresh pork loins from a commercial facility were evaluated based on 1-day postmortem pH value and ultimately classified as high/normal (5.90–6.46, x̄ = 6.09; n = 25) and low/normal (5.59–5.71, x̄ = 5.67; n = 25). Instrumental color and drip loss were determined on 1-day postmortem chops (2.54 cm). The remaining chops were individually vacuum packaged, aged 1, 7, or 14 d postmortem at 4°C, and then frozen until further analyses. Intramuscular lipid and moisture content was determined through proximate analysis. Instrumental star probe tenderness was evaluated on cooked chops (68°C) from each aging time. Trained sensory panel evaluation and cooking loss were determined on cooked, 14-d postmortem chops. Western blot analysis examined the presence of desmin degradation products within low ionic strength extracts of longissimus thoracis. Based on the pH categories, star probe tenderness, drip loss, cook loss, palatability traits, meat color measurements, and the presence of desmin degradation products were significantly different, whereas intramuscular lipid content was not different. High/normal pH chops had lower L values at 1-d (P < 0.01) and at 14-d postmortem (P < 0.01). Drip loss was greater (P < 0.01) in 1-d low/normal pH chops, as was cooking loss at each aging time (P < 0.01). The trained sensory panel rated high/normal pH loins as juicier (P < 0.01), more tender (P < 0.01), and less chewy (P < 0.05). High/normal pH chops had lower star probe values compared to low/normal pH chops at 1 (P < 0.05), 7 (P < 0.01), and 14 (P < 0.01) d postmortem. High/normal pH chops exhibited a greater proportion of samples containing desmin degradation products within the low ionic strength extract at each aging time (P < 0.01). Variation in 1-d postmortem pH contributes to differences in measurable quality characteristics of fresh pork loin and impacts the presence of desmin degradation products in low ionic strength extracts.