Modeling the combined impact of water activity and temperature on <i>Salmonella</i> Montevideo thermal inactivation on dried chili peppers

Salmonella contamination in low-moisture foods remains a continuing food safety and public health problem. The World Health Organization ranked unprocessed red chili peppers as the spice with the highest risk of Salmonella contamination in a risk assessment-based report in 2022. Therefore, appropriate mitigation strategies are required to control Salmonella contamination in dried chilies. The objectives of this research were to investigate thermal inactivation of Salmonella on dried chili peppers at a_w 0.33-0.97 and estimate thermal resistance parameters under isothermal and dynamic conditions. The dried chili peppers were inoculated with S. Montevideo and conditioned in a humidity-controlled chamber to achieve the a_w of 0.33, 0.50, and 0.97. The samples were placed into 1-mm thick aluminum test cells and heated at 55, 60, 65, and 70°C to estimate the thermal inactivation parameters using the log-linear/modified-Bigelow model. The results showed that the a_w played a key role in accurately describing Salmonella lethality on dried chili pepper. At 65°C, a 3-log reduction of S. Montevideo required 100 min at a_w = 0.33, compared to only 20 min at a_w = 0.50. The modified Bigelow model under dynamic conditions described inactivation significantly better (root mean squared error [RMSE] = 0.646 and corrected Akaike information criterion [AIC_c] = -120.97) than the modified Bigelow model under isothermal conditions (RMSE = 0.707 and AIC_c= -76.71). This study provides the food industry with valuable data to optimize thermal processing conditions and improve safety protocols for chili-based products, thereby reducing the risk of Salmonella contamination.