Phosphate and two-stage cooking: Impact on lipid oxidation and tenderness in sous-vide beef semitendinosus

The study investigated phosphate's effects on tenderness and lipid oxidation in beef cooked sous-vide. Semitendinosus beef cuts were treated with 0.15% and 0.3% sodium tripolyphosphate (STPP), and plain water (0% STPP). These cuts were then sous-vide cooked at two different temperatures, 60 °C and 70 °C, for two different durations, 3 h and 6 h. Analytical techniques including Warner-Bratzler shear force (WBSF), pH, thiobarbituric acid reactive substances (TBARS), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR) were employed. STPP concentration did not yield a statistically significant impact on the pH and FTIR spectrum of sous-vide beef (p > 0.05). However, STPP markedly enhanced tenderness by loosening the myofibril structure (observed in SEM) and weakening myosin and actin bands (observed in SDS-PAGE). This improvement led to lower WBSF values with 0.3% STPP, particularly noticeable at 60 °C for 6 h. Additionally, 0.3% STPP delayed lipid oxidation, evidenced by lower oxidation values after 4 weeks of refrigerated storage at 4 °C. These findings highlight STPP's potential to improve tenderness and lipid oxidation stability in sous-vide beef.