Biochemical and physicochemical changes in spent hen breast meat during postmortem aging

An experiment was conducted to study the biochemical and physicochemical changes with respect to improvement in tenderness of spent hen breast meat. Breast muscle obtained from freshly slaughtered spent hens (72 wk old) was divided into 5 equal lots and dipped in 1 mM NaN3 before being packed in low-density polyethylene pouches under aerobic conditions and stored at refrigeration temperature (4 C). Lots were removed on 0, 7, 14, 21, and 28 d of storage and analyzed for pH, TBA reactive substances (TBARS), total sulfhydryl content, protein-bound sulfhydryl content, nonprotein-bound sulfhydryl content, perimysial fraction, collagen content, free OH-proline, N, nonprotein N, and proteolysis rate. Shear force value and penetrometer readings were also determined after making patties from the stored muscle samples. Results showed that pH values were gradually decreasing over the storage period. The TBARS values were increasing (P < 0.001), whereas the sulfhydryl content was decreasing (P < 0.001) over the storage period. The TBARS values were negatively (P < 0.05) correlated with total sulfhydryl content. This suggests that sulfhydryl content may prevent further higher oxidation of lipids. The soluble collagen content, collagen solubility, free OH-proline, and proteolysis rate were increasing (P < 0.001) during postmortem aging. These results suggest that collagen degradation into free amino acids occurs postmortem. A gradual decrease (P < 0.001) in shear force value and a gradual increase (P < 0.001) in penetrometer readings were recorded in the patties made from matured breast meat. Therefore, postmortem aging of spent hen breast meat resulted in 23% improvement in tenderness of minced patties on 14 d and 39% on 28 d as evidenced by biochemical and physicochemical changes.