Effect of eggshell calcium acetate on postmortem proteolysis and tenderization of spent duck muscle

The purpose of this study was to investigate the effect of eggshell calcium acetate on postmortem proteolysis and tenderization of Tsaiya duck muscle. Duck carcasses were obtained from a government-regulated slaughterhouse and chilled at 12 °C for 1 h. Both sides of the breast muscles were excised and incubated individually in either eggshell calcium acetate solution containing 30 mM Ca²⁺ (ECA, N = 15), 30 mM calcium acetate (ACA, N = 15), or 30 mM EDTA (EDTA, N = 15) at 5 °C for 3 days. The control group (CON, N = 15) was incubated in double-distillated water at 5 °C for 3 days. Breast muscle samples from the right side of each carcass were taken at 0 (1 h postmortem), 1, 2, and 3 days of incubation for pH determination, casein zymography, and Western blotting. Samples from the left side of each breast were taken for myofibrillar fragmentation index (MFI) and shear force measurements at 1 and 3 days of incubation. The results showed that the decrease in calpain-1 and calpain-11 activities, and desmin content was more rapid in the ECA- and ACA-incubated samples compared to the CON and EDTA-incubated samples during the 3-day incubation period. On the other hand, the MFI increased significantly in the ECA- and ACA-incubated samples compared to the CON and EDTA-incubated samples, while shear force values decreased more in the ECA- and ACA-incubated samples than in the CON and EDTA-incubated samples. Our results suggest that eggshell calcium acetate, like calcium acetate, can effectively enhance postmortem proteolysis and tenderizing of spent duck breast muscles.