Elizabeth J Frankish

Fresh apples are expected to have a minimal risk of causing foodborne illness from Escherichia coli O157:H7 because of their low pH and refrigerated storage under modified atmosphere. To assess this expectation, improve understanding of the various factors that contribute to risk, and identify potential risk management improvements to maintain low risk a quantitative risk assessment model was developed to estimate the risk of illness from Australian apples throughout the apple supply chain. The model incorporated orchard conditions, proportion of apples damaged, effects of storage time and temperature on pathogen survival through the supply chain, and orchard and packhouse activities that affect contamination levels. The model was constructed in Analytica® with uncertainty in predictions modelled through use of 150,000 (5 × 30,000) iterations. Alternative scenarios of orchard management practices, wash water controls, equipment cleaning, and verification activities were examined using current Australian harvest guidelines and water washing as a baseline. The mean risk of illness from E. coli O157:H7 after consuming fresh Australian apples was estimated to be 1.43 × 10−10 per serving (min. 0, max. 1.21 × 10−6) or approximately one illness per 10 billion apples consumed. Under a scenario with conservative (i.e., worst-case) assumptions, one case of E. coli O157:H7 illness every five years, caused by fresh apples in Australia was predicted. Sensitivity analyses indicated that wash water control, removal of damaged fruit, and prevention of cross-contamination were the most crucial factors affecting the predicted number of illnesses. Despite the adoption of several conservative assumptions to fill identified data gaps, it is predicted that Australian apples have a low probability of causing foodborne illness. Nonetheless, this risk assessment will assist industry to reinforce risk management best practices for risk mitigations against E. coli on apples.