Optimization of rosemary extract-based immersion processing for improving color stability and quality of tuna flesh.

BACKGROUND: Tuna flesh is highly susceptible to oxidative quality deterioration during storage, resulting in discoloration and reduced consumer acceptance. This study aimed to evaluate antioxidant-rich natural extracts and optimize a rosemary extract-based immersion process to improve color stability and overall quality of tuna flesh. RESULTS: Among seven natural extracts evaluated, rosemary extract exhibited the highest antioxidant activity and total phenolic content and was therefore selected for process optimization. Single-factor experiments revealed non-linear effects of immersion solution concentration, immersion time and immersion ratio on tuna surface redness. Response surface methodology was subsequently applied to determine the optimal immersion conditions, and the developed quadratic models demonstrated high predictive accuracy. Under optimized conditions, rosemary extract-treated tuna showed enhanced surface redness, increased oxy-myoglobin retention and improved sensory acceptability. Furthermore, during chilled storage at 4 and 10 °C, optimized rosemary extract immersion effectively suppressed microbial growth, reduced total volatile basic nitrogen accumulation, inhibited myoglobin oxidation and maintained superior sensory quality compared to untreated samples. CONCLUSION: Optimized rosemary extract immersion effectively improved color stability and preserved the overall quality of tuna during chilled storage. These findings suggest that rosemary extract immersion represents a practical clean-label strategy for enhancing the shelf-life and marketability of tuna products. © 2026 Society of Chemical Industry.