Inactivation of Escherichia coli O157:H7 and Salmonella by gamma irradiation of alfalfa seed intended for production of food sprouts.
Inonizing irradiation was determined to be a suitable method for the inactivation of Salmonella and Escherichia coli O157:H7 on alfalfa seed to be used in the production of food sprouts. The radiation D (dose resulting in a 90% reduction of viable CFU) values for the inactivation of Salmonella and E. coli O157:H7 on alfalfa seeds were higher than the D-values for their inactivation on meat or poultry. The average D-value for the inactivation of Salmonella on alfalfa seeds was 0.97 +/- 0.03 kGy; the D-values for cocktails of meat isolates and for vegetable-associated isolates were not significantly different. The D-values for nonoutbreak and outbreak isolates of E. coli O157:H7 on alfalfa seeds were 0.55 +/- 0.01 and 0.60 +/- 0.01 kGy, respectively. It was determined that the relatively high D-values were not due to the low moisture content or the low water activity of the seed. The D-values for Salmonella on alfalfa seeds from two different sources did not differ significantly, even though there were significant differences in seed size and water activity. The increased moisture content of the seed after artificial inoculation did not significantly alter the D-value for the inactivation of Salmonella. The results of this study demonstrate that 3.3- and 2-log inactivations can be achieved with a 2-kGy dose of ionizing radiation, which will permit satisfactory commercial yields of sprouts from alfalfa seed contaminated with E. coli O157:H7 and Salmonella, respectively.
Thayer
Donald W
DW
Food Safety Intervention Technologies Research Unit, U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, Pennsylvania 19038, USA. dthayer@arserrc.gov
Rajkowski
Kathleen T
KT
Boyd
Glenn
G
Cooke
Peter H
PH
Soroka
Douglas S
DS
D004307:Dose-Response Relationship, Radiation; D019453:Escherichia coli O157 / Q000254:growth & development / Q000528:radiation effects*; D005514:Food Irradiation; D005516:Food Microbiology; D005720:Gamma Rays; D000455:Medicago sativa / Q000382:microbiology*; D012475:Salmonella / Q000254:growth & development / Q000528:radiation effects*; D012639:Seeds / Q000382:microbiology* / Q000648:ultrastructure; D014867:Water
D014867:Water