Factors affecting the efficacy of chlorine against Escherichia coli O157:H7 and Salmonella on alfalfa seed
2002
Fett, W.F.
Factors affecting the efficacy of chlorine treatment for elimination of bacteria pathogens from laboratory-inoculated alfalfa seed, the ability of chlorine to eliminate Salmonella Muenchen from naturally contaminated alfalfa seed, and the effect of chlorine treatment on germination of several types of sprouting seed were evaluated. Initial water temperature (15, 22 or 40 degrees C) did not affect the rate or amount of free chlorine released from Ca(OCl)2 during 30 min of stirring. Residual chlorine was detected after 15 min of stirring at the highest ratio of seed to volume of chlorine [50 g seed to 50 ml of 3% (w/v) Ca(OCl)2] tested. Of the 29 types of sprouting seed treated for 10 min with buffered (to pH 6.8) 3.0% Ca(OCl)2, only the germination of spelt and hard, soft and Kamut wheat was drastically reduced. Treatment (10 min) of laboratory-inoculated seed with buffered (to pH 6.8) 2.5 or 3.0% (w/v) Ca(OCl)2 along with water rinses both before and after treatment led to a significant reduction (3.9-4.5 log cfu g(-1)) of Escherichia coli O157:H7 and Salmonella, but not their elimination. Efficacy of chlorine treatment was reduced in the absence of buffer. Altering treatment times to 5 or 20 min did not affect treatment efficacy. A 1 h presoak of seed in tap water before chlorine treatment was beneficial, but led to a greatly reduced germination percentage after treatment. Addition of low levels of surfactant had no effect on treatment efficacy. Treatment (10 min with continuous agitation) of alfalfa seed naturally contaminated with Salmonella Muenchen with buffered or unbuffered 3.0% (w/v) Ca(OCl)2, but not with buffered 0.3% (w/v) Ca(OCl)2, eliminated the pathogen from the seed.
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