Redox modulation by rosemary phenolics and ultrasound affects nitrite reactivity, pigment formation, and oxidative stability in cooked pork batters

This study investigated how rosemary extract and ultrasound modulate curing-related redox reactions in cooked pork batters formulated with and without sodium nitrite, using sodium erythorbate as a conventional curing accelerator. Five formulations were evaluated: (i) sodium nitrite (250 ppm) + sodium erythorbate (250 ppm), (ii) sodium nitrite, (iii) sodium erythorbate, (iv) sodium nitrite + rosemary extract (250 ppm), and (v) rosemary extract. Each formulation was treated with or without ultrasound (25 kHz, 650 W, 20 min), resulting in ten treatments. Changes in pH, oxidation-reduction potential (ORP), residual nitrite, nitrosylmyoglobin content, protein and lipid oxidation, and instrumental color were evaluated immediately after processing and after 7 days of storage at 5 °C. The rosemary extract was characterized by a predominance of the lipophilic diterpene carnosic acid, along with lower concentrations of hydrophilic phenolics such as protocatechuic and caffeic acids. The presence of these compounds contributed to lower ORP values (P < 0.05) in rosemary-containing treatments, indicating a more reducing environment in the meat matrix. Sodium erythorbate, particularly in combination with ultrasound, resulted in higher nitrosylmyoglobin levels, whereas rosemary extract reduced lipid and protein oxidation and color changes during refrigerated storage (P < 0.05). Ultrasound enhanced pigment formation and, in specific formulations, reduced residual nitrite levels (P < 0.05). These results suggest that curing reactions are influenced by redox conditions, which may affect nitrite conversion within the meat matrix.