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
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Use
of Green Fluorescent Protein Expressing Salmonella Stanley To Investigate
Survival, Spatial Location, and Control on Alfalfa Sprouts Journal
of Food Protection: Vol. 64, No. 12, pp. 1891–1898. Megha
Gands, Sherene Golding, Sima Yaron, and Karl R. Matthews Cook
College, Department of Food Science, Rutgers, The State University of New Jersey Abstract—Laser scanning
confocal microscopy (LSCM) was used to observe the interaction of Salmonella
Stanley with alfalfa sprouts. The green fluorescent protein (gfp) gene was
integrated into the chromosome of Salmonella Stanley for constitutive
expression, thereby eliminating problems of plasmid stability and loss of
signal. Alfalfa seeds were inoculated by immersion in a suspension of Salmonella
Stanley (ca. 107 CFU/ml) for 5 min at 22°C. Epifluorescence
microscopy demonstrated the presence of target bacteria on the surface of
sprouts. LSCM demonstrated bacteria present at a depth of 12 um within intact
sprout tissue. An initial population of ca. 104 CFU/g seed increased
to 7.0 log CFU/g during a 24-h germination period and then decreased to 4.9 log
CFU/g during a 144-h sprouting period. Populations of Salmonella Stanley on
alfalfa seeds decreased from 5.2 to 4.1 log CFU/g and from 5.2 to 2.8 log CFU/g
for seeds stored 60 days at 5 and 22°C, respectively. The efficacy of 100, 200,
500, or 2,000 ppm chlorine in killing Salmonella Stanley associated with sprouts
was determined. Treatment of sprouts in 2,000 ppm chlorine for 2 or 5 min caused
a significant reduction in populations of Salmonella Stanley. Influence of
storage on Salmonella Stanley populations was investigated by storing sprouts 4
days at 4°C. The initial population (7.76 log CFU/g) of Salmonella Stanley on
mature sprouts decreased (7.67 log CFU/g) only slightly. Cross-contamination
during harvest was investigated by harvesting contaminated sprouts, then
directly harvesting noncontaminated sprouts. This process resulted in the
transfer of ca. 105 CFU/g Salmonella Stanley to the noncontaminated
sprouts. |