Development and Validation of a Novel Gas-Washing Bottle Incubation System (GBIS) for Monitoring Microbial Growth in Liquid Media Under Well-Controlled Modified Atmosphere Conditions

The transition towards more sustainable packaging calls for improving our ability to predict, control, and inhibit microbial growth. Despite the importance of modified atmosphere packaging (MAP) in food preservation, the exact relations between MAP gases (CO₂, O₂, N₂) and microbial behavior are still poorly understood. Addressing this major knowledge gap requires a specific infrastructure to gain precise control over the gas composition during storage time. Thus, this study aimed at developing and validating an innovative gas-washing bottle incubation system (GBIS) with an adapted pH methodology for monitoring microbial growth in liquid media under different well-controlled conditions. <i>Listeria monocytogenes</i>-a psychrotrophic pathogen raising severe safety concerns under refrigerated conditions-was used as a representative microorganism. The results showed that daily gas flushing effectively dominated overnight headspace variations, allowing incubating <i>L. monocytogenes</i> and daily sampling for 13 days under static conditions. Subsequently, storage experiments were performed at 4 °C under stable pH and anaerobic conditions with different CO₂ levels (20-40-60%). Significant growth reduction was observed from 6.0 to 4.8 log CFU/mL as CO₂ increased from 20% (pH = 6.7) to 60% (pH = 6.2) (<i>p</i> ≤ 0.05). Overall, GBIS shows great potential in data collection for predictive modeling and, consecutively, for boosting decision-making in the food packaging sector.