International Specialty Supply
Supplying Sprout Companies Throughout the World
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International Specialty Supply Supplying Sprout Companies Throughout the World
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820 East 20th Street Cookeville, TN 38501 USA 931 526 1106
| Organic Acid and Hypochlorite Treatments
for Sprouts; Efficacy of Novel Organic Acid and Hypochlorite Treatments for
Eliminating Escherichia Coli O157:H7 from Alfalfa Seeds Prior to Sprouting ABSTRACT
(Reformatted so that people other than nurds can read it) This
study investigated novel two-step organic acid/hypochlorite treatments as
alternatives to 20,000 ppm active chlorine (from calcium hypochlorite) for
eliminating Escherichia coli O157:H7 from alfalfa seeds prior to sprouting.
Commercially available alfalfa seeds were inoculated with a five-strain E. coli
O157:H7 mixture and dried to attain ca. 106 CFU/g of seeds. Seeds then underwent
one of several soak treatments including: 1) 5%
(v/v) lactic acid for 10 min at 42C, 2) 5%
acetic acid (v/v) for 10 min at 42C, 3)
2.5% lactic acid for 10 min at 42C followed by 2,000 ppm active chlorine (from
calcium hypochlorite) for 15 min at 25C, 4) 5%
lactic acid for 10 min at 42C followed by 2000 ppm active chlorine for 15 min at
25C, or 5)
20,000 ppm active chlorine for 15 min at 25C. Each
treatment reduced numbers of inoculum cells by about 6.0 log10 CFU/g as
determined by plating on Sorbitol MacConkey agar (SMac). Plating on
non-selective Brain Heart Infusion agar (BHI) showed that treatments 1 - 4
reduced counts by 2.3 - 4.1 log10 CFU/g, thus indicating a large proportion of
injured cells. Successive
lactic acid and hypochlorite treatments (treatments 3 and 4) were more lethal
than either organic acid alone (treatments1 and 2). No
surviving cells were detected on SMac or BHI following treatment with 20,000 ppm
active chlorine (treatment 5). Regardless
of the previous treatment, E. coli O157:H7 counts increased to 107 - 108 CFU/g
during sprouting. Germination of seeds was not adversely affected by any of the
treatments (germination > 90%). Results
of this study show that: a)
non-lethal cell injury must be considered when evaluating intervention
treatments against E. coli O157:H7 on alfalfa seeds, b)
reductions of 2 - 4 log10 CFU/g can be attained without using 20,000 ppm active
chlorine, c)
successive lactic acid and hypochlorite treatments have greater lethality than
organic acid treatments alone, and d)
none of the treatments tested can prevent regrowth of surviving E. coli O157:H7
during sprouting. Barbara
Ingham has generously offered to send a reprint of this article to anyone who
would like a copy. She can be reached at bhingham@facstaff.wisc.edu |