Background & Aim: The use of synthetic additives is one of the main approaches for preventing microbial growth and oxidative reactions in meat products. These preservatives were recently marked as unhealthy to humans; therefore, the consumers demand for fresh, natural, and negligibly processed products with lower content of artificial additives is increasing.Experimental: The effect of Satureja bachtiarica Bunge essential oil (EO) and tomato powder (TP) to optimize sausage formulation with reduced nitrite content was investigated. Response surface methodology (RSM) was used to investigate the effects of different levels of EO (200-400 ppm), TP (5-15%) as Hurdles, and sodium nitrite (SN) (0-300 ppm) in sausage formulation during storage (0- 24 days). Dependent variables including residual nitrite, pH, color indices, microbial load, and hardness were investigated and finally model optimization and validation were conducted.Results: The results showed that residual nitrite was strongly depending on initial added nitrite and storage time (p<0.001), so the use of nitrite substituent was undeniable to have an improved sausage formulation without microbial defect. RSM represented a quadratic model for all responses except in texture which was linear and the pH and microbial load showed interaction. The optimized predicted values for SN, EO and TP were 56 ppm, 378 ppm and 5%, respectively. The model validation revealed that the results of the experiments were in good agreement with the predicted values.Recommended applications/industries: The results of the present study can be useful for consideration in meat products industry to reduce the nitrite level in sausage formulation. پرونده مقاله