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Comparison of chemical treatments to eliminate enterohemorrhagic Escherichia
coli O157:H7 on alfalfa seeds.
J Food Prot.
1999 Apr;62(4):318-24.
Taormina
PJ, Beuchat LR.
Center for Food Safety and Quality Enhancement, Department of Food Science and
Technology,
University of
Georgia,
Griffin 30223-1797, USA.
The focus of this study was to determine the efficacy of various chemicals in
eliminating 2.04 to 3.23 log10 CFU/g of Escherichia coli O157:H7 from alfalfa
seeds and to determine the survivability of the pathogen on seeds stored for
prolonged periods at three temperatures. Significant (P < or = 0.05) reductions
in populations of E. coli O157:H7 on inoculated seeds were observed after
treatments with 500 and 1,000 ppm of active chlorine (as Ca[OCl]2) for 3 but not
10 min and with > or =2,000 ppm of Ca(OCl)2 regardless of pretreatment with a
surfactant. Treatment with 20,000 ppm of active chlorine failed to kill 2.68
log10 CFU/g of seeds. Acidified NaClO2 (500 ppm) was effective in reducing
populations of the pathogen by >2 logs per g. Acidified ClO2 significantly
reduced populations of E. coli O157:H7 on seeds at concentrations > or =100 ppm,
and 500 ppm of ClO2 reduced the pathogen from 2.7 log10 CFU/g to <0.5 CFU/g.
Chlorine (as NaOCl) was not effective at concentrations < or =1,000 ppm;
significant reduction was achieved only after treatment with 2,000 ppm for 3 or
10 min. Notable reduction in populations was observed after treatment with 30 or
70% C2H3OH, but there was a dramatic decrease in germination percentage.
Treatment with 0.2% H2O2 significantly reduced populations, and the organism was
not detected by direct plating after treatment with > or =1% H2O2. Significant
reduction in population of E. coli O157:H7 occurred after treatment with 1%
trisodium phosphate, 40 ppm of Tsunami and Vortexx, and 1% Vegi-Clean. A
significant decrease in the number of E. coli O157:H7 on dry seeds was observed
within 1 week of storage at 25 and 37 degrees C, but not at 5 degrees C. Between
1 and 38 weeks, populations on seeds stored at 5 degrees C remained relatively
constant. The pathogen was recovered from alfalfa seeds initially containing
3.04 log 10 CFU/g after storage at 25 or 37 degrees C for 38 weeks but not 54
weeks.
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