Use of spent irrigation water for microbiological analysis of alfalfa sprouts

Numerous outbreaks of foodborne illness have been linked to the consumption of raw sprouts. Sprout producers have been advised by the Food and Drug Administration to include microbiological testing of spent irrigation water during production as part of an overall strategy to enhance the safety of sprouts. Alfalfa sprouts and irrigation water were analyzed to show the feasibility of using irrigation water for monitoring the microbiological safety of sprouts. Sprouts and water were produced and harvested from both commercial-scale (rotary drum) and consumer-scale (glass jars) equipment. Rapid increases of aerobic mesophiles occurred during the first 24 h of sprouting, with maximum levels achieved after 48 to 72 h. The counts in irrigation water were on average within approximately 1 log of their respective counts in the sprouts. Similar results were obtained for analysis of Escherichia coli O157:H7 in irrigation water and sprouts grown from artificially inoculated seeds. Testing of spent irrigation water indicated the contamination status of alfalfa sprouts grown from seeds associated with outbreaks of Salmonella infection.