Mathematical Modeling of Salmonella Inactivation During Apple Drying and Pre-Drying Heating in Closed Environments

Area of Science:

• Food Science
• Microbiology
• Food Preservation

Background:

• Drying is crucial for food preservation, but microbial safety concerns, particularly from Salmonella, have emerged in low-moisture products.
• Understanding pathogen inactivation during drying is vital for preventing foodborne illnesses.

Purpose of the Study:

• To develop a predictive model for Salmonella inactivation in diced apples during hot air drying and high-humidity heating.
• To evaluate the influence of process conditions (temperature, humidity) on Salmonella thermal inactivation.

Main Methods:

• Diced apples inoculated with Salmonella were subjected to three treatments: open-box hot air drying (90°C), closed-box pre-drying heating (90°C), and closed-box pre-drying heating (70°C).
• Sample temperature, air temperature, and relative humidity (RH) were monitored, and Salmonella survival was quantified over time.

Main Results:

• High-humidity pre-drying heating achieved a 5-log reduction of Salmonella significantly faster (8.5 min at 90°C, 14 min at 70°C) than open-box drying (28.7 min at 90°C).
• A mathematical model incorporating sample surface RH and temperature accurately predicted Salmonella inactivation (RMSE = 0.92, R² = 0.86).

Conclusions:

• High humidity plays a critical role in enhancing microbial reduction during food drying processes.
• High-humidity pre-drying heating is an effective strategy for controlling Salmonella in foods like apples.
• The developed predictive model can be used for real-time microbial inactivation assessment in dynamic drying environments.