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Mathematical modeling and assessment of microbial migration during the sprouting
of alfalfa in trays in a nonuniformly contaminated seed batch using enterobacter
aerogenes as a surrogate for Salmonella Stanley
15.nov.07
Journal of Food Protection®, Volume 70, Number 11, November 2007 , pp.
2602-2605(4)
Liu, Bin; Schaffner, Donald W.
ABSTRACT: Raw seed sprouts have been implicated in several food poisoning
outbreaks in the past 10 years. The U.S. Food and Drug Administration recommends
that sprout growers use interventions (such as testing of spent irrigation
water) to control the presence of pathogens in the finished product. During the
sprouting process, initially low concentrations of pathogen may increase, and
contamination may spread within a batch of sprouting seeds. A model of pathogen
growth as a function of time and distance from the contamination spot during the
sprouting of alfalfa in trays has been developed with Enterobacter aerogenes .
The probability of detecting contamination was assessed by logistic regression
at various time points and distances by sampling from sprouts or irrigation
water. Our results demonstrate that microbial populations and possibility of
detection were greatly reduced at distances of ≥20 cm from the point of
contamination in a seed batch during tray sprouting; however, the probability of
detecting microbial contamination at distances less than 10 cm from the point of
inoculation was almost 100% at the end of the sprouting process. Our results
also show that sampling irrigation water, especially large volumes of water, is
highly effective at detecting contamination: by collecting 100 ml of irrigation
water for membrane filtration, the probability of detection was increased by
three to four times during the first 6 h of seed germination. Our findings have
quantified the degree to which a small level of contamination will spread
throughout a tray of sprouting alfalfa seeds and subsequently be detected by
either sprout or irrigation water sampling.
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