Probabilistic exposure assessment model to estimate aseptic-UHT product failure rate

Area of Science:

• Food Science and Technology
• Microbiology
• Risk Assessment Modeling

Background:

• Aseptic-Ultra-High-Temperature (UHT) processing aims to eliminate microorganisms for shelf-stable products.
• Critical control points include sterilization and aseptic handling to prevent microbial contamination.
• Key microbial hazards for low-acid aseptic UHT products are Clostridium botulinum, Bacillus cereus, and Geobacillus stearothermophilus spores.

Purpose of the Study:

• To develop and utilize a probabilistic exposure assessment model to evaluate the sterility failure rate (SFR) of aseptic-UHT products.
• To identify critical contamination pathways and modules contributing to microbial hazards.
• To assess the risk posed by Clostridium botulinum, Bacillus cereus, and Geobacillus stearothermophilus.

Main Methods:

• A Modular Process Risk Model with nine modules was developed to simulate contamination from raw materials, sterilization, and post-sterilization recontamination.
• The model incorporated 42 controlled settings and over 55 probabilistic inputs, utilizing @Risk software for Monte Carlo simulations.
• Sterility Failure Rate (SFR) was calculated per batch and analyzed after each module to pinpoint high-risk stages.

Main Results:

• Geobacillus stearothermophilus exhibited the highest SFR (380,000 contaminated bottles per 10^11 produced), primarily due to its thermal resistance and survival of UHT treatment.
• Bacillus cereus contributed a significant SFR (17,000 contaminated bottles per 10^11 produced), with major sources identified as airborne recontamination of the aseptic tank (49%) and post-sterilization packaging contamination (33%).
• Clostridium botulinum showed the lowest SFR (3 contaminated bottles per 10^11 produced).

Conclusions:

• The developed probabilistic model effectively assesses sterility failure rates in aseptic-UHT production for key bacterial hazards.
• Geobacillus stearothermophilus poses the most significant risk due to its heat resistance.
• Reducing Bacillus cereus-related SFR requires addressing airborne contamination in aseptic tanks and post-sterilization packaging hygiene.