Survival of Salmonella Typhimurium in Vacuum-Sealed Maize Tortillas During Refrigerated and Ambient Storage

As dietary habits evolve, cereal-based foods, such as maize tortillas, are increasingly consumed as ready-to-eat products, yet their physicochemical properties may influence microbial stability during storage. This study characterized the microbiological and physicochemical properties of commercial vacuum-sealed maize tortillas and evaluated Salmonella enterica survival in vacuum-sealed laboratory-prepared maize tortillas. Nine commercial brands were characterized by proximate composition, moisture content, water activity (0.945–0.965), and pH (4.76–5.50), confirming a high-moisture and carbohydrate-rich matrix. Indicator microorganisms revealed moderate contamination levels, with total coliforms exceeding regulatory limits in several samples. Challenge studies demonstrated that S. Typhimurium survival at 4 and 25 °C followed non-linear inactivation kinetics accurately described by the Weibull model (R2 > 0.90). Storage temperature significantly affected the shape parameter (p = 0.026), whereas packaging conditions significantly influenced the estimated 5-log reduction time (t5). Vacuum-sealed tortillas exhibited prolonged pathogen survival, particularly under refrigeration (>60 days), where bacterial populations remained detectable for extended storage periods. These findings challenge the assumption that vacuum-sealing improves microbiological safety in cereal-based foods.