Purpose: Reduction of inoculated generic E. coli levels was observed on apples varieties with and without EC water application for up to two weeks.
Methods: A four-strain, rifampicin-resistant generic E. coli cocktail was inoculated onto apples of selected varieties (Gala and Golden Delicious) with or without EC and harvested from three canopy positions (high, low outside, low inside). For examination of survival on mature fruit near harvest (short-term) varieties were sampled at 0, 2, 10, 18, 34, 42, 58, 82, 106, and 154 hours, for examination of longer-term survival on immature fruit, apples were collected at: 0, 2, 8, 32, (56 or 80), 104, 152, and 320 hours post-inoculation.
Results: Initial inoculum levels on apples ranged from 6.8-7.7 log CFU generic E. coli/apple. Rapid die-off of 0.7-3.8 log CFU/apple was observed for generic E. coli in the first 8-10 hours, between sun-set and sunrise. For the short-term study, Gala apples at 10 hours, untreated, average reduction in generic E. coli was over 2.5 log CFU/apple and for treated Gala over 3.5 log CFU/apple. For the long-term study, untreated Gala apples averaged a 3.7 log reduction of generic E. coli during the first 8 hours post-inoculation and the EC treated Gala apples averaged a 3.8 log reduction.
Significance: Treatment with EC did not appear to enhance survival of generic E. coli on apples compared to the response on control apples that did not receive EC application.