3.2. Inactivation of pathogenic bacteria by RF heating
The survival of S. Typhimurium and E. coli O157:H7 in creamy
peanut butter during 90 s of RF heating are shown in Table 1. The
populations of both pathogens decreased with increasing treatment
time. Significant (P > 0.05) reductions were not observed for
50 s compared to the control. However, treatment for 70 s significantly
(P < 0.05) reduced levels of S. Typhimurium and E. coli
O157:H7 by 2.77 and 2.93 log CFU/g in creamy peanut butter,
respectively. After 90 s of RF treatment, the reductions of S.
Typhimurium and E. coli O157:H7 were 4.29 and 4.39 log CFU/g in
creamy peanut butter, respectively. Table 2 shows populations of S.
Typhimurium and E. coli O157:H7 in chunky peanut butter during
90 s of RF heating. There were no significant (P > 0.05) reductions in
microbial levels until 30 s of treatment had occurred. However,
significant reductions of S. Typhimurium and E. coli O157:H7 were
observed after 50 s of treatment. Treatment for 90 s significantly
(P < 0.05) reduced levels of S. Typhimurium by 4.55 log CFU/g and
E. coli O157:H7 by 5.32 log CFU/g.