COST ACTION 920

Inventory of QMRA Studies in Europe

Pathogen

 E. coli O157:H7

Country or region

 United States

Transmission route

 From

 Apples

To

Finished cider product

Specific product(s)

 Apple cider

End-point(s)

Concentration of E. coli O157:H7 in apple cider

Bibliographic reference

Duffy, S and Schaffner, D.W.  2002. Monte Carlo Simulation of the Risk of Contamination of Apples with Escherichia coli O157:H7.  International Journal of Food Microbiology, 78(3): 245-255.

Duffy,S.; Schaffner,D.W.  2001.  Modeling the survival of Escherichia coli O157:H7 in apple cider using probability distribution functions for quantitative risk assessment.  Journal of Food Protection, 64(5): 599-605.

Abstract

Quantitative descriptions of the frequency and extent of contamination of apple cider with pathogenic bacteria were obtained using literature data and computer simulation. Probability distributions were chosen to describe the risk of apple contamination by each suspected pathway. Tree-picked apples may be contaminated by birds infected with Escherichia coli O157:H7 when orchards were located near a sewage source (ocean or landfill). Dropped apples could become contaminated from either infected animal droppings or from contaminated manure if used as fertilizer. We also developed probability distribution functions for the change in concentration of E. coli O157:H7 (log CFU/day) in cider.  Six storage conditions (refrigeration [4 to 5°C]; temperature abuse [6 to 10°C]; room temperature [20 to 25°C]; refrigerated with 0.1% sodium benzoate, 0.1% potassium sorbate, or both) were modeled.  A risk assessment model was created in Analytica. The results of worst-case simulations revealed that 6–9 log CFU E. coli O157:H7 might be found on a harvest of 1000 dropped apples, while 3–4 log CFU contamination could be present on 1000 tree-picked apples. This model confirms that practices such as using dropped apples and using animal waste as fertilizer increase risk in the production of apple cider, and that pasteurization may not eliminate all contamination in juice from heavily contaminated fruit. E. coli survival rate data for all three unpreserved cider storage conditions were highly peaked, and these data were fit to logistic distributions: ideal refrigeration, logistic (-0.061, 0.13); temperate abuse, logistic (-0.0982, 0.23); room temperature, logistic (-0.1, 0.29) and uniform (-4.3, -1.8), to model the very small chance of extremely high log CFU reductions.  There were fewer published studies on refrigerated, preserved cider, and these smaller data sets were modeled with beta (4.27, 2.37) x 2.2 - 1.6, normal (-0.2, 0.13), and gamma (1.45, 0.6) distributions, respectively.  Simulations were run to show the effect of storage on E. coli O157:H7 during the shelf life of apple cider.  Under every storage condition, with and without preservatives, there was an overall decline in E. coli O157:H7 populations in cider although a small fraction of the time a slight increase was seen. 

Status

 Published

Availability

 http://foodsci.rutgers.edu/schaffner/pdf%20files/duffy%20IJFM%202002.pdf

Institute

 Food Science Department, Rutgers University

Contact person

Don Schaffner

Partners

Siobain Duffy