title: Combined effect of low-dose irradiation and acidified sodium chlorite washing on Escherichia coli O157:H7 inoculated on mung bean seeds.
abstract: The effect of low-dose irradiation (0.75 and 1.5 kGy) in combination with acidified sodium chlorite (ASC) on the reduction of Escherichia coli O157:H7 on mung bean seeds was examined. Washing with ASC (0.2, 0.5, 0.8, and 1.2 g/L sodium chlorite and 1.0 g/L citric acid) for 2 h reduced the E. coli O157:H7 population from 5.2 to 2.3-3.3 log CFU/g, depending on the concentrations of sodium chlorite. Gamma ray irradiation at 0.75 and 1.5 kGy resulted in reductions of about 1.8 and 2.8 log CFU/g, respectively. Therefore, a single treatment with ASC washing or gamma ray irradiation at 0.75 or 1.5 kGy could not achieve the complete elimination of E. coli O157:H7 on mung bean seeds. Conversely, low-dose irradiation (0.75 and 1.5 kGy) followed by washing with ASC (0.5-1.2 g/L) reduced the population of E. coli O157:H7 to below the detection limit (<1 log CFU/g). However, E. coli O157:H7 was detected in most samples in the enrichment and germination studies. When the treatment order was reversed (ASC washing followed by low-dose irradiation), the E. coli O157:H7 population was also observed to be below the detection limit. Under this treatment, fewer samples (16.7%) were shown to be positive in the enrichment and germination studies, and complete elimination was not achieved. The germination rates of mung bean seeds were not affected by ASC washing and gamma irradiation; however, the yield and length of sprouts were decreased by gamma irradiation.
authors.affiliation: Food Hygiene Laboratory, National Food Research Institute, Kannondai 2-1-12, Tsukuba, Japan. nei@affrc.go.jp
authors.forename: Daisuke
authors.initials: D
authors.lastname: Nei
authors.forename: Md Latiful
authors.initials: ML
authors.lastname: Bari
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Inatsu
authors.forename: Susumu
authors.initials: S
authors.lastname: Kawasaki
authors.forename: Setsuko
authors.initials: S
authors.lastname: Todoriki
authors.forename: Shinichi
authors.initials: S
authors.lastname: Kawamoto
mesh_terms: D002712:Chlorides / Q000494:pharmacology*; D015169:Colony Count, Microbial; D019453:Escherichia coli O157 / Q000187:drug effects* / Q000302:isolation & purification / Q000528:radiation effects*; D007887:Fabaceae / Q000382:microbiology*; D005514:Food Irradiation / Q000379:methods; D005516:Food Microbiology; D005720:Gamma Rays; D018525:Germination / Q000187:drug effects / Q000528:radiation effects; D006863:Hydrogen-Ion Concentration; D027805:Phaseolus; D012639:Seeds / Q000382:microbiology*
chemical_list: D002712:Chlorides; C001599:chlorite