Use of Spent Irrigation Water for Microbiological Analysis of Alfalfa Sprouts

Abstract

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.

Monte Carlo Simulation of Pathogen Behavior during the Sprout Production Process

“…Relevant literature was grouped into two main subject categories: growth of pathogens during sprouting (1,8,16,19,33,41,42,47,49) and pathogen detection on seeds or sprouts (8,15,20,21,23,36,45,48,55,59). Epidemiological literature was reviewed to assemble a comprehensive understanding of primary risk factors in the sprouting process (3,4,9,25,29,30,35,37,52,53,58).…”

“…Fu et al performed the most thorough comparison of spent irrigation water and sprouts, using both naturally occurring total aerobic mesophiles and inoculated E. coli O157:H7. They found, on average 1 log 10 CFU/g or ml more on sprouts than in irrigation water for both naturally occurring floras and inoculated E. coli O157:H7 (15).…”

Flow cytometry for rapid detection of Salmonella spp. in seed sprouts

“…A number of approaches have been developed for more rapid testing of Salmonella in alfalfa or other types of sprouts (e.g. mung bean) and in SIW, including commercially available immunoassay [39] or custom amperometric immunoassay [40], standard PCR [41], automated fiber optic biosensor [42], or automated nucleic acid sensor [38]. Pre-analytical sample preparation is an indispensible element in successful navigation from sample to answer [43].…”

“…Pre-analytical sample preparation is an indispensible element in successful navigation from sample to answer [43]. Sample preparation methods used in conjunction with assays for Salmonella in sprouts include simple centrifugation [41] or filtration [39] and TFF [40,44]. Reported levels of sensitivity for detection of Salmonella in SIW were 100 CFU L 1 (0.1 CFU ml 1 ) for standard PCR [41], ∼300 CFU ml 1 for combined TFF and amperometric immunoassay [40] and 8 Â 10 5 CFU ml 1 for automated PCR (reported as 10 4 CFU per 12.5 ml sample of SIW) [38].…”

Natural Antimicrobials for Biopreservation of Sprouts

“…The seeds usually carry microbial loads comprised between 3 and 6 log CFU/g, including pseudomonads and enterobacteriaceae as main components (Andrews et al, 1982;Prokopowich and Blank, 1991;Robertson et al, 2002;Splittstoesser et al, 1983). The bacterial load increases rapidly during the sprouting process, reaching from 6 to 8 log CFU/g after two days in one study (Fu et al, 2001) and between 7.8 and 8.8 in another (Weiss et al, 2007). Other reports have indicated final counts of up to 8-9 log CFU/g in commercial sprouts (Patterson and Woodburn, 1980;Prokopowich and Blank, 1991).…”