TABLE 1.

Effect of pressure treatments for 2 or 5 min in combination with mild heat on inactivation of E. coli O157:H7 on alfalfa seedsa

Pressure level (MPa)Log survivors (CFU/g) (mean ± SD) after treatment at the following temp and pressure treatment timeb:
40°C45°C50°C
2 min5 min2 min5 min2 min5 min
2503.5 ± 0.3NDNDND1 ± 0.35ND
3002.9 ± 0.5ND<0.8 (3)<0.8 (2)<0.8 (0)ND
350<0.8 (3)<0.8 (2)<0.8 (1)<0.8 (2)<0.8 (0)ND
400<0.8 (2)<0.8 (1)<0.8 (1)<0.8 (0)<0.8 (0)ND
450<0.8 (1)<0.8 (1)<0.8 (0)<0.8 (0)<0.8 (0)ND
500<0.8 (1)<0.8 (1)<0.8 (1)<0.8 (0)<0.8 (0)ND
550<0.8 (0)ND<0.8 (0)ND<0.8 (0)ND
  • a The initial populations of E. coli O157:H7 on inoculated and dried seeds were 5.7 log CFU/g, as determined by plating appropriate dilutions on TSAYE-N.

  • b The number of survivors (log survivors [CFU/g]) after treatment at three temperatures for 2 or 5 min at different pressures. Data representing log survivors (CFU/g) are the means of three replicates. The numbers in parentheses are the number of samples testing positive after enrichment out of a total of three trials. ND, not done.