Reducing The Risk Of Future Outbreaks

Several steps can be taken to minimize the risk of future sprout-related outbreaks of foodborne illness including the use of good agricultural practices (GAPs) during the production of sprouting seed as detailed in several recent government, university, and produce organization publications [122-124]. Sprout seed is obtained from plants grown in the open field and thus subject to potential contamination by nonpotable irrigation water, manure, domestic and wild animals, birds, farm machinery, and farm workers. To the author's knowledge, there are no fields in the U.S. or elsewhere designated solely for the production of seed destined for use by sprout growers. Settings on harvesting machinery should be such as to minimize damage to the seed. Cross contamination between clean and contaminated lots of harvested seed can occur in seed cleaning (conditioning) facilities and also when lots of seed are mixed before packaging and distribution. Several salmonella serovars were detected in the waste streams of a seed-cleaning machine in a U.S. alfalfa seed-cleaning facility indicating the presence of salmonella in the local alfalfa fields where the seed originated [125]. Seed-cleaning machines should be thoroughly cleaned and sanitized before and between lots of seed destined for sprouting. Seed scarification has been used historically to increase the germinability of seed lots that contain a significant amount of hard seed. Scarification involves the mechanical abrasion of the seed coat to allow for entry of water facilitating germination. Damage to the seed coat may make elimination of bacterial pathogens by treatment with chemical sanitizers more difficult [62,81] and probably should be avoided if possible. There is also the potential for contamination during transit and storage of seed as well as during seed germination, growth, and harvest.

Commercial sprout growers need to follow good manufacturing practices (GMPs) and have written standard sanitation operating procedures (SSOPs) and a hazard analysis and critical control point (HACCP) plan in place [126]. Growers should be thoroughly familiar with the recommendations contained in the FDA guidance documents which include detailed methods for testing of spent irrigation water for salmonella and E. coli O157:H7 [53]. Seed should be of high quality and all bags of seed should be inspected for evidence of rodent activity (gnawed holes and presence of urine stains using a blacklight). Thorough testing of all lots of sprout seed for bacterial pathogens is desirable and should reduce the risk of sprout-related outbreaks of foodborne disease. A sampling and testing protocol for use with sprout seed for human pathogens has been proposed [127]. However, due to the sporadic and low level of contamination with human pathogens often encountered, a negative sample test cannot guarantee that the entire lot is pathogen free. Thus, an effective, approved seed-sanitizing step should be applied by the grower, and the spent irrigation water or sprouts should be tested for the presence of pathogens. Irrigation water needs to be of high quality and the use of well water also requires regular testing for adequate levels of residual chlorine. Postharvest contamination of sprouts can occur during transit, storage, display, and by cross contamination in restaurant or home kitchens and adequate precautions need to be taken.

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