Survival of Generic Escherichia coli on Bulk and Wrapped d'Anjou Pears under Extended Storage Durations

Due to past outbreaks and recalls linked to tree fruit, more targeted food safety risk mitigation measures are needed in the pear industry. However, there is limited research on food safety risks that are specific to pear packing operations. This study examined the survival of generic Escherichia coli on both unwrapped (bulk) and wrapped in commercial paper (containing 1.3% copper carbonate and 0.1% ethoxyquin) d'Anjou pears under extended periods of controlled atmosphere storage (4℃; 2-3% O₂ and 1% CO₂). Whole, fresh green d'Anjou pears were inoculated (∼7 log CFU/pear) with a three-strain cocktail of rifampicin-resistant generic E. coli and stored for up to 252 d. Nine pear samples were collected at 13 timepoints, and E. coli concentrations were enumerated. To determine the die-off pattern of E. coli on pears, data were modeled using log-linear, Weibull, and segmented regression approaches. E. coli was still detectable at ∼1.9 log CFU/pear after 252 d regardless of bulk or wrapped storage. Based on Akaike Information Criterion (AIC), a segmented model, with four distinct die-off phases and wrapping as a covariate, best fit E. coli survival on pear surfaces over time. Die-off was best characterized by an initial decline rate of 0.151 log CFU/pear/d from 0 to 8.74 d followed by slower rates of 0.030, 0.014, and 0.010 log CFU/pear/d between 8.74-55.97 d, 55.97-172.02 d, and 172.02-252 d, respectively. These findings provide evidence to inform practical, risk-based control measures for the pear industry.