Apple Drying Process Lethality Prediction Using Response Surface Methodology.

Area of Science:

• Food Science
• Microbiology
• Drying Technology

Background:

• Hot-air drying is crucial for preserving apple products.
• Ensuring microbial safety, like Salmonella inactivation, is paramount in dried foods.
• Predicting microbial lethality during drying requires understanding process parameters.

Purpose of the Study:

• To evaluate the impact of drying temperature, bed depth, and airflow on Salmonella inactivation in apple cubes.
• To establish water activity (a_w) as a proxy for microbial lethality during hot-air drying.
• To develop and validate a response surface methodology (RSM) model for predicting Salmonella inactivation.

Main Methods:

• Utilized a Box-Behnken design to test 15 drying conditions.
• Inoculated apple cubes with Salmonella and dried them to a target water activity (a_w) of 0.60.
• Employed RSM to model the relationship between drying parameters and Salmonella inactivation.

Main Results:

• Salmonella inactivation showed a strong linear correlation with water activity reduction (R² = 0.91-0.97).
• Inactivation ranged from 2.25 to 4.97 log CFU/4 cubes at a_w 0.60.
• Higher temperature and airflow increased lethality, while increased bed depth decreased it; airflow's effect lessened with depth.

Conclusions:

• Water activity reduction is a reliable indicator of microbial lethality in hot-air apple drying.
• The developed RSM model accurately predicts Salmonella inactivation under various processing conditions.
• Optimizing drying parameters can enhance microbial safety in dried apple products.